- Email: [email protected]
How to improve mouse cloning
Theriogenology xxx (xxxx) xxx
Contents lists available at ScienceDirect
Theriogenology journal homepage: www.theriojournal.com
How to improve mouse cloning Atsuo Ogura a, b, c, * a
RIKEN BioResource Research Center, Ibaraki, 305-0074, Japan Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki, 305-8572, Japan c RIKEN Cluster for Pioneering Research, Saitama, 351-0198, Japan b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 15 January 2020 Accepted 18 January 2020 Available online xxx
The mouse is the most extensively used mammalian laboratory species in biology and medicine because of the ready availability of a wide variety of defined genetic and gene-modified strains and abundant genetic information. Its small size and rapid generation turnover are also advantages compared with other experimental animals. Using these advantages, somatic cell nuclear transfer (SCNT) in mice has provided invaluable information on epigenetics related to SCNT technology and cloning, playing a leading role in relevant technical improvements. These improvements include treatment with histone deacetylase inhibitors, correction of Xist gene expression (controlling X chromosome inactivation), and removal of methylated histones from SCNT-generated embryos, which have proven to be effective for SCNT cloning of other species. However, even with the best combination of these treatments, the birth rate in cloned offspring is still lower than intracytoplasmic sperm injection (ICSI) or in vitro fertilization (IVF). One remaining issue associated with SCNT is placental enlargement (hyperplasia) found in late pregnancy, but this abnormality might not be a major cause for the low efficiency of SCNT because many SCNT-derived embryos die before their placentas start to enlarge at midgestation (early postimplantation stage). It is known that, at this stage, undifferentiated trophoblast cells in the extraembryonic tissue of SCNT-derived embryos fail to proliferate. Understanding the molecular mechanisms is essential for further technical improvements of mouse SCNT, which might also provide clues for technical breakthroughs in mammalian SCNT and cloning in general. © 2020 Elsevier Inc. All rights reserved.
Keywords: Genomic imprinting Mouse Oocyte Somatic cell nuclear transfer Zygotic gene activation
1. What does mouse SCNT tell us? Somatic cell nuclear transfer (SCNT) in mammals is the sole reproductive technology that can produce a genetic copy of an animal from a single donor somatic cell [1,2]. Although its applications are enormous in basic biology as well as industry and medicine, the birth rates of cloned animals have been generally much lower than those of other reproductive techniques such as intracytoplasmic sperm injection (ICSI) or in vitro fertilization (IVF) [3]. The low efficiency of cloning following SCNT can be attributed to either genetic or epigenetic causes. While the former causes might arise accidentally and randomly, the latter causesdat least in partdoccur inevitably and nonrandomly, mostly representing differences between the epigenomes of germ and somatic cells [4,5]. Therefore, for technical improvements of SCNT, the most rational approach is to identify the epigenetic
* RIKEN BioResource Research Center, Ibaraki, 305-0074, Japan. E-mail address: [email protected].
abnormalities that are found in all or the majority of embryos and/ or their placentas, and then seek for methodology to correct these epigenetic abnormalities [5]. An alternative way for improving SCNT is to identify the cell types and genotypes of donor cells that ensure higher cloning efficiencies. The laboratory mouse (Mus musculus domesticus) might provide the best model for these strategies thanks to the presence of genetically defined strains, the availability of a large amount of genetic information, and relatively easy generation of gene-modified animals. Wakayama et al. first produced cloned mice using cumulus cells from the hybrids of two inbred strains, C57BL/6 and DBA/2 (BDF1), and BDF1 oocytes [6]. Since then, this combination of donor cells and oocytes has been the standard for mouse cloning by SCNT, which enables comparison of cloning efficiencies wherever it is performed (Fig. 1). The high reproductive performance, short gestation period, and rapid generation turnover are also major advantages of the mouse as a laboratory species. Furthermore, the easy correction of a number of in vivo-matured oocytes of high quality is also an important advantage of the mouse for SCNT studies [7]; in other species such
https://doi.org/10.1016/j.theriogenology.2020.01.038 0093-691X/© 2020 Elsevier Inc. All rights reserved.
Please cite this article as: Ogura A, How to improve mouse cloning, Theriogenology, https://doi.org/10.1016/j.theriogenology.2020.01.038
2
A. Ogura / Theriogenology xxx (xxxx) xxx
Fig. 1. Improvements in mouse SCNT cloning. (A) Since the first report of successful mouse cloning by Wakayama et al. [6], the use of B6D2F1 cumulus cells as donors and B6D2F1 oocytes has been the standard for mouse cloning by SCNT. (B) This enables the reliable comparison of different technical improvements between different laboratories. This is one of the best merits of mouse SCNT [68].
as the pig, in vitro maturation of oocytes can significantly affect SCNT outcome [8,9]. Since the first report of successful mouse SCNT cloning by Wakayama et al. [6], we have focused for a long time on how to improve this approach. In the first 10 years, we assessed donor somatic cells from different cell types and different genotypes, and concluded ultimately that there was no relationship between cloning efficiency and the undifferentiated state of donor cells, and that the presence of the 129 strain genome significantly improved cloning efficiency [10] (Fig. 2). As a result, many mouse cloned offspring with a variety of cell types (e.g., NKT cells, hematopoietic stem cells, neural stem cells, and primordial germ cells) were born using the C57BL/6 129 F1 hybrid genotype [11e14]. It is also noteworthy that Wakayama’s group has successfully propagated many generations of cloned mice by serial SCNT using cumulus cells with the BDF1 129/Sv F1 genetic background [15]. The 129 strain is also known as that in which the first embryonic stem cell line was established [16,17]. These results have led us to assume that 129 mouse genome has an exceptionally high genomic plasticity, but we do not know the underlying molecular mechanisms. After a number of SCNT trials using recombinant inbred strains between C57BL6 and 129, we have narrowed down the genomic regions responsible for the genomic plasticity of the 129 strain into four separate regions located on chromosomes 2, 5, 8, and 19 [18]. Full understanding of these mechanisms will contribute to significant improvements in SCNT cloning as well as refinement of other genomic reprogramming-related technologies such as the generation of induced pluripotent cells. 2. Epigenetic characteristics of SCNT-generated mouse embryos The abnormal epigenetic characteristic first identified for SCNT-derived embryos was DNA hypermethylation in bovine preimplantation embryos [19]. That study showed that donor-type DNA methylation was maintained in a specific interspersed nuclear element sequence during preimplantation development. To overcome this problem, many studies have attempted to decrease the DNA methylation level of SCNT-derived embryos by treatment of donor cells or reconstructed embryos with DNA
methyltransferase (DNMT) inhibitors such as azacytidine. Although improved development into blastocysts were reported in some cases [20,21], this strategy did not lead to technical breakthroughs in SCNT probably because no or only minor effects on the birth rates have been reported. The first technical breakthrough in SCNT methodology was achieved in mouse cloning by using trichostatin A (TSA), a potent histone deacetylate inhibitor [22,23] (Fig. 1B). Interestingly, TSA exerts its best effect when it is administered to reconstructed embryos, but not to the donor cells before nuclear transfer. It is very probable that the synergistic effects of the loosened chromatin state induced by TSA and the maternal (ooplasmic) chromatin-modifying factors might be a key for success. Our comparative transcriptome analysis using TSAtreated SCNT-derived embryos, non-treated SCNT-derived embryos, and IVF-derived embryos revealed that the effects of TSA were not random, but specifically increased the expression levels of genes linked to zygotic gene activation (ZGA), which occurs at the 2-cell embryo stage in mice [24]. It is generally assumed that zygotic activation proceeds with de novo activation of transcription factors, which then activate another layer of genes encoding transcription factors. Indeed, we identified that one of the upstream ZGA genes, Spic, was activated in TSA-treated SCNT-derived embryos, but not in nontreated embryos. Interestingly, injection of mRNA for the Spic gene alone into SCNT-derived embryos resulted in a transcriptional profile resembling TSA-treated embryos produced by SCNT and IVF. The TSA treatment was proven to be effective for SCNT of other species such as pigs, bovines, and monkeys [25e27]. Similarly, other histone deacetylate inhibitors such as suberoylanilide hydroxamic acid (SAHA) or scriptaid are reported to improve development of cloned embryos in mice, followed by many other species [28e32]. Thanks to the recent advent of next generation sequence technology, RNA-sequencing (RNA-seq) has become available for the detailed transcriptome analysis of mammalian preimplantation embryos. Matoba et al. employed this technology for the analysis of SCNT- and IVF-derived mouse embryos and identified the inactive genomic regions specific for SCNT-derived embryos’ reprogramming-resistant regions (RRRs) [33]. Based on existing chromosome immunoprecipitation (ChIP)-sequencing data for mouse somatic cells, they found that RRRs are enriched for H3K9me3 and its removal by the ectopically expressed H3K9me3 demethylase Kdm4d greatly improved SCNT efficiency (Fig. 1B). Interestingly, a comparison of the effects of TSA and Kdm4d on SCNT-derived embryos indicated that both target the H3K9me3repressed genes in somatic cells, but Kdm4d treatment released their repressive state more extensively by expanding the active areas including centric/pericentric repeat sequences [33]. The Kdm4d treatment was found to improve the development of SCNT-derived embryos significantly in humans and cynomolgus monkeys, resulting in the production of nuclear transfer-derived embryonic stem cells (ntESCs) and cloned monkeys [27,34]. It is well known that SCNT-derived embryos in humans and primates are very hard to culture beyond the stage of ZGAdaround the 16cell stage in these speciesdand ntESCs can only be established at low efficiency [35]. These studies revealed that the major reprogramming barrier in these species is H3K9me3 derived from the donor cell genome. For further identification of reprogramming barriers in a stage-specific manner, Liu et al. combined embryo biopsy and single-cell sequencing for SCNT-derived mouse embryos. They found that inactivation of Kdm4b and Kdm5b functioned as barriers for the 2-cell and 4-cell arrest stages of SCNT-derived embryos, respectively. Indeed, coinjection of mRNAs for Kdm4b and Kdm5b could restore the transcriptional profiles of SCNT-derived embryos and improve the production of cloned mice [36].
Please cite this article as: Ogura A, How to improve mouse cloning, Theriogenology, https://doi.org/10.1016/j.theriogenology.2020.01.038
A. Ogura / Theriogenology xxx (xxxx) xxx
3
Fig. 2. The presence of the 129 strain genome significantly increased the cloning efficiency. (A) B6 129 F1 Sertoli cells gave the best birth rate (>10%) without TSA. Two-way analysis of variance revealed that both the cell type (cumulus Sertoli) and the genotype had significant effects on the birth rate, and that there was a significant interaction between them, indicating that the combination of these two factors may affect the SCNT outcome. (B) The 129 genome enhances the genomic reprogramming of hematopoietic stem cells. More than half of the cloned embryos developed into blastocysts expressing EGFP-Oct4. Data are from Refs. [10,12].
Another transcriptome analysis using SCNT-derived mouse blastocysts revealed that SCNT-specific downregulation predominantly occurred in X-linked genes [37]. This was caused by ectopic expression of the Xist gene, which is responsible for X chromosome inactivation in mammalian cells [38]. In female preimplantation embryos in mice, but not humans and rabbits, Xist is exclusively expressed from the paternal allele so that the dosage of X-linked genes in female embryos (XX) is maintained at the same level as in male embryos (XY). Our large-scale nuclear transfer experiments using somatic cells and germ cells at different developmental stages suggested that Xist is expressed at the 4-cell stage as a default and that this is repressed in the maternal allele by imprinting established during the last stage of oogenesis [39]. Later, it was confirmed that this imprint was dependent on H3K27me3 [40], consistent with the previous notion thatdunlike other canonical imprinting systemsdthis Xist imprint did not depend on DNA methylation [41]. As it is erased in the embryonic linage after implantation, somatic cells have lost this memory. Therefore, cloned embryos derived from somatic cells have no Xist-repressing imprint and Xist is expressed in both maternal and paternal alleles, leading to the aberrant repression of X-linked genes. Surprisingly, correction of the Xist expression pattern in SCNT-derived embryos by Xist gene knockout or knockdown resulted in a nearly 10-fold increase in the birth rates of clones [37,42] (Fig. 1B). However, the knockdown strategy was effective only in male SCNT-derived embryos because of the inability of allele-specific repression of Xist by conventional siRNA injection [43]. In pigs, Xist knockdown also improved the developmental competence of male SCNT-derived embryos, although a longer blocking effect on Xist by injection with shRNA plasmids, rather than siRNA injection, was necessary [44]. It is important to note that correction of the Xist expression pattern is effective in the rescue of early postimplantation embryos following SCNT [42], in contrast to the predominant improvement of preimplantation SCNT-derived embryos by Kdm4d treatment [33]. Consistent with this, maternal Xist knockout of donor cells and Kdm4d mRNA injection into reconstructed embryos had a synergistic effect and their combination increased the birth rates to as high as 18.7% and 23.5% with cumulus and Sertoli cells, used as donors, respectively [45] (Fig. 1B).
3. Abnormal placental development following mouse SCNT The placenta is the organ that facilitates the maternalefetal exchanges of gases, nutrients, and all other supplies necessary for fetal growth, while separating the fetal and maternal circulations. The placenta has attracted special attention from cloning researchers because SCNT is often associated with morphological abnormalities of placentas even in cases of normal delivery of cloned offspring [46]. In mouse SCNT, it is well known that placental enlargement (placentomegaly) inevitably occurs during the late gestation period [47,48] (Fig. 3A and B). This enlargement is predominantly caused by an expansion of the spongiotrophoblast (ST) layer (the junctional zone) that includes swollen ST cells with enlarged endoplasmic reticulum and an increased number of glycogen storage cells [48,49] (Fig. 3B and C). As a very similar placental phonotype also appears in interspecies crosses (e.g., M. musculus M. spretus) and Esx1 knockout mice, Fundele et al. attempted to identify the causative genes by comparative transcriptome analysis using enlarged placentas from these three different sources including SCNT-derived embryos and from normal control placentas derived by natural mating of laboratory mice [50]. However, only one gene of known function (Ramp2) and one gene of unknown function were found common to all three types of enlarged placentas [50]. It is conceivable that, because the histology of enlarged placentas is much different from that of control placentas, differentially expressed genes in each experimental group might have simply reflected the results of aberrant placental histology. As placental enlargement occurs in most clones, there should be some primary key mechanism(s) that are always associated with mouse SCNT. As far as we and others have observed, the technical breakthroughs so far achieved, such as corrections of Xist or H3K9me3-repressed genes, have never ameliorated the aberrant placental phenotype [33,37]. Therefore, we should seek for other epigenetic errors that might impair placental, rather than fetal, development. In this context, placentaspecific imprinted genes might be probable candidates. Previously, we have identified loss of imprinting (LOI) of three placentaspecific imprinted genes, Gab1, Sfmbt2, and Slc38a4, in SCNTderived placentas [51]. This was further confirmed using SCNT-
Please cite this article as: Ogura A, How to improve mouse cloning, Theriogenology, https://doi.org/10.1016/j.theriogenology.2020.01.038
4
A. Ogura / Theriogenology xxx (xxxx) xxx
Fig. 3. Placental enlargement associated with mouse SCNT. (A and B) This placental phenotype is characterized by the enlarged spongiotrophoblast (ST) layer, an irregular spongiotrophoblastelabyrinthine (LB) cell boundary and proliferation of glycogen-rich cells. (C) The enlargement of the ST layer is causeddat least in partdby cell hypertrophy with expanded rough endoplasmic reticulum (ER; arrows).
derived trophoblast stem cells [52]. LOI leads to biallelic expression of these genes, which might have caused placental enlargement, because it was reported that these genes can positively regulate placental development based on observations of mutant forms of these genes [53e55]. Therefore, we employed a maternal gene knockout strategy to recover a normal paternal expression, as we did for the rescue of ectopic Xist expression in cloned embryos. However, the maternal knockout of either of the genes did not decrease the placental size at term following SCNT. These placentaspecific, paternally expressed imprinted genes are reported to be regulated by a histone mark, H3K27me3 [56]. We further examined the possible involvement of other H3K27me3-regulated imprinted genes in the enlargement of SCNT-derived placentas and finally identified a set of downstream genes responsible for this phenotype [57]. It will be interesting to examine whether the expressions of these genes are also altered in interspecies hybrids or Esx1 gene knockout placentas. Thus, the major cause for the enlargement of SCNT-derived placentas has been identified, but we also found that this placental phenotype does not significantly affect the development of SCNT-derived embryos. Indeed, the stage at which most SCNT-derived mouse embryos die is the early postimplantation period without placental enlargement (embryo days, E6.5eE9.5). During this stage, paradoxically, the SCNT-derived extraembryonic tissues show poor development because of the low proliferating ability of undifferentiated trophoblast cells that express Cdx2, Esrrb, and Eomes [58,59]. This early placental anomaly might be the next target for further improvement of mouse SCNT. 4. Potential applications of SCNT One of the important purposes of mammalian SCNT is the production of genetic copies from valuable animals. It might even be possible to produce cloned offspring from dead individuals or resurrect the genotypes of extinct animals. In 2007, the world’s first
clone of a family dog, Missy, was born using her cryopreserved somatic cells [60]. Cells recovered from the 28,000-year-old frozen remains of a woolly mammoth showed spindle assembly, histone incorporation, and partial nuclear formation, although the nuclei were too damaged to go further [61]. In laboratory mice, duplication of genetically unidentified mutants might prove practical, especially when the phenotype is dependent on the unknown genetic background. It is desirable for donor cells that are ready for use to be repeatedly collected without damaging the donor animals. For this purpose, we examined the possibility of using (nucleated) leukocytes collected from a drop of peripheral blood as SCNT donor cells. The leukocyte suspension was prepared by lysing the erythrocytes. Using fluorescence-activated cell sorting, we found that most nucleated cells >8 mm in diameter were granulocytes or monocytes. We confirmed that both putative granulocytes/monocytes and lymphocytes could be used for cloning mice by SCNT [62]. Because the use of lymphocytes will result in the birth of offspring with DNA rearrangements, we applied granulocyte/monocyte cloning to two genetically modified strains and two recombinant inbred strains, and offspring were obtained from all four strains tested [62]. This strategy could be applied to the rescue of infertile founder animals or a “last-of-line” animal possessing invaluable genetic resources. A calf was also born from a leukocyte using a serial cloning method, in which somatically cloned blastomeres (compacting morulae) were subjected to a second round of nuclear transfer [63]. Later, Wakayama’s group reported that sediment cells in urine can be used for the production of cloned mice and ntESCs [64]. This should be one of the most invasive ways to make genetic copies of animals by SCNT. As mentioned above, the use of lymphocytes as donor cells results in the production of cloned animals carrying rearranged DNA in their whole body. Hochedlinger and Jaenisch produced “monoclonal mice” derived from mature B- and T-cells via ntESC and chimera generation [65] and Inoue et al. generated NKT cell-
Please cite this article as: Ogura A, How to improve mouse cloning, Theriogenology, https://doi.org/10.1016/j.theriogenology.2020.01.038
A. Ogura / Theriogenology xxx (xxxx) xxx
derived cloned mice by direct SCNT [11]. In either case, the offspring carried the expected DNA rearrangements. Taking advantage of this feature, we generated cloned mice that carry endogenously rearranged T-cell receptor (TCR) genes from CD4þ T cells specific for antigens, mite antigens, and ovalbumin, which had been administered to the donor animals [66]. The pre-rearranged TCR alleles of the clones were transmitted to the offspring, allowing us to establish a set of mouse lines. They showed chronic-type allergic phenotypes, and bronchial and nasal inflammation upon local administration of the corresponding antigens [66]. These mouse lines are available from our center for research use (https:// mus.brc.riken.jp/en/). Thus, SCNT can be used for the generation of new mouse strains for research. One of the biggest technical challenges inherent to SCNT is the inflexibility of the sex of the offspring. Cloning male cells inevitably results in the birth of male, not female neonates, and vice versa. This sex irreversibility might become an important issue, especially when sexual breeding must be resumed for subsequent propagation, for example in projects for the resurrection of extinct species or the rescue of endangered species. While we were producing cloned mice using Sertoli cells as nuclear donors, one female mouse was born accidentally. This “male-derived female” clone grew into a normal adult and produced offspring by natural mating with a littermate [67]. Chromosomal analysis revealed that the female clone had a 39,X karyotype (XO or Turner syndrome), indicating that the Y chromosome had been deleted in the donor cell or at some early step during the SCNT procedure. This finding suggests the possibility of resuming sexual reproduction after cloning a single male animal, as XO females could be fertile, as in the case of this mouse. In conclusion, mouse SCNT may provide us with invaluable information on mammalian developmental epigenetics as well as experimental models for biomedical researches. So far, we have successfully cloned all types of somatic cells we tested, provided they had a normal chromosomal constitution and normal genomic imprinting. Thus, although the differentiation-associated memories are highly variable, they might be easily reprogramed at nuclear transfer. By contrast, genome-wide somatic epigenetic marks imposed at implantation (such as repressive histone marks) seem to be more rigid, but their number may be limited. Therefore, we might be able to achieve high-yield SCNT cloning outcomes by targeting fewer epigenetic errors than originally anticipated. Acknowledgment A part of this study was supported by Grants-in-Aid from the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) (Nos. 25112009 and 19H05758) and Epigenome Manipulation Project of the All-RIKEN Projects. References [1] Gurdon JB. Nuclear transplantation, the conservation of the genome, and prospects for cell replacement. FEBS J 2017;284:211e7. [2] Miyamoto K. Various nuclear reprogramming systems using egg and oocyte materials. J Reprod Dev 2019;65:203e8. [3] Loi P, Iuso D, Czernik M, Ogura A. A new, dynamic era for somatic cell nuclear transfer? Trends Biotechnol 2016;34:791e7. [4] Ogura A, Inoue K, Wakayama T. Recent advancements in cloning by somatic cell nuclear transfer. Philos Trans R Soc Lond B Biol Sci 2013;368: 20110329. [5] Matoba S, Zhang Y. Somatic cell nuclear transfer reprogramming: mechanisms and applications. Cell Stem Cell 2018;23:471e85. [6] Wakayama T, Perry ACF, Zuccotti M, Johnson KR, Yanagimachi R. Full-term development of mice from enucleated oocytes injected with cumulus cell nuclei. Nature 1998;394:369e74. [7] Hasegawa A, Mochida K, Inoue H, Noda Y, Endo T, Watanabe G, Ogura A. Highyield superovulation in adult mice by anti-inhibin serum treatment combined with estrous cycle synchronization. Biol Reprod 2016;94:21.
5
[8] Kim MJ, Oh HJ, Choi YB, Lee S, Setyawan EMN, Lee SH, Lee SH, Hur TY, Lee BC. Suberoylanilide hydroxamic acid during in vitro culture improves development of dog-pig interspecies cloned embryos but not dog cloned embryos. J Reprod Dev 2018;64:277e82. [9] Wang X, Zhu X, Liang X, Xu H, Liao Y, Lu K, Lu S. Effects of resveratrol on in vitro maturation of porcine oocytes and subsequent early embryonic development following somatic cell nuclear transfer. Reprod Domest Anim 2019;54:1195e205. [10] Inoue K, Ogonuki N, Mochida K, Yamamoto Y, Takano K, Kohda T, Ishino F, Ogura A. Effects of donor cell type and genotype on the efficiency of mouse somatic cell cloning. Biol Reprod 2003;69:1394e400. [11] Inoue K, Wakao H, Ogonuki N, Miki H, Seino K, Nambu-Wakao R, Noda S, Miyoshi H, Koseki H, Taniguchi M, Ogura A. Generation of cloned mice by direct nuclear transfer from natural killer T cells. Curr Biol 2005;15:1114e8. [12] Inoue K, Ogonuki N, Miki H, Hirose M, Noda S, Kim JM, Aoki F, Miyoshi H, Ogura A. Inefficient reprogramming of the hematopoietic stem cell genome following nuclear transfer. J Cell Sci 2006;119:1985e91. [13] Inoue K, Noda S, Ogonuki N, Miki H, Inoue S, Katayama K, Mekada K, Miyoshi H, Ogura A. Differential developmental ability of embryos cloned from tissue-specific stem cells. Stem Cells 2007;25:1279e85. [14] Miki H, Inoue K, Kohda T, Honda A, Ogonuki N, Yuzuriha M, Mise N, Matsui Y, Baba T, Abe K, Ishino F, Ogura A. Birth of mice produced by germ cell nuclear transfer. Genesis 2005;41:81e6. [15] Wakayama S, Kohda T, Obokata H, Tokoro M, Li C, Terashita Y, Mizutani E, Nguyen VT, Kishigami S, Ishino F, Wakayama T. Successful serial recloning in the mouse over multiple generations. Cell Stem Cell 2013;12:293e7. [16] Evans MJ, Kaufman MH. Establishment in culture of pluripotential cells from mouse embryos. Nature 1981;292:154e6. [17] Martin GR. Isolation of a pluripotent cell line from early mouse embryos cultured in medium conditioned by teratocarcinoma stem cells. Proc Natl Acad Sci U S A 1981;78:7634e8. [18] Inoue K, Ogura A. In quest of genomic treasure. J Reprod Dev 2015;61:489e93. [19] Kang YK, Koo DB, Park JS, Choi YH, Chung AS, Lee KK, Han YM. Aberrant methylation of donor genome in cloned bovine embryos. Nat Genet 2001;28: 173e7. [20] Enright BP, Kubota C, Yang X, Tian XC. Epigenetic characteristics and development of embryos cloned from donor cells treated by trichostatin A or 5-aza20 -deoxycytidine. Biol Reprod 2003;69:896e901. [21] Enright BP, Sung LY, Chang CC, Yang X, Tian XC. Methylation and acetylation characteristics of cloned bovine embryos from donor cells treated with 5-aza20 -deoxycytidine. Biol Reprod 2005;72:944e8. [22] Kishigami S, Mizutani E, Ohta H, Hikichi T, Thuan NV, Wakayama S, Bui HT, Wakayama T. Significant improvement of mouse cloning technique by treatment with trichostatin A after somatic nuclear transfer. Biochem Biophys Res Commun 2006;340:183e9. [23] Rybouchkin A, Kato Y, Tsunoda Y. Role of histone acetylation in reprogramming of somatic nuclei following nuclear transfer. Biol Reprod 2006;74: 1083e9. [24] Inoue K, Oikawa M, Kamimura S, Ogonuki N, Nakamura T, Nakano T, Abe K, Ogura A. Trichostatin A specifically improves the aberrant expression of transcription factor genes in embryos produced by somatic cell nuclear transfer. Sci Rep 2015;5:10127. https://doi.org/10.1038/srep10127. [25] Li J, Svarcova O, Villemoes K, Kragh PM, Schmidt M, Bogh IB, Zhang Y, Du Y, Lin L, Purup S, Xue Q, Bolund L, Yang H, Maddox Hyttel P, Vajta G. High in vitro development after somatic cell nuclear transfer and trichostatin A treatment of reconstructed porcine embryos. Theriogenology 2008;70:800e8. [26] Iager AE, Ragina NP, Ross PJ, Beyhan Z, Cunniff K, Rodriguez RM, Cibelli JB. Trichostatin A improves histone acetylation in bovine somatic cell nuclear transfer early embryos. Clon Stem Cells 2008;10:371e9. [27] Liu Z, Cai Y, Wang Y, Nie Y, Zhang C, Xu Y, Zhang X, Lu Y, Wang Z, Poo M, Sun Q. Cloning of macaque monkeys by somatic cell nuclear transfer. Cell 2018;172:881e7. e7. [28] Ono T, Li C, Mizutani E, Terashita Y, Yamagata K, Wakayama T. Inhibition of class IIb histone deacetylase significantly improves cloning efficiency in mice. Biol Reprod 2010;83:929e37. [29] Van Thuan N, Bui HT, Kim JH, Hikichi T, Wakayama S, Kishigami S, Mizutani E, Wakayama T. The histone deacetylase inhibitor scriptaid enhances nascent mRNA production and rescues full-term development in cloned inbred mice. Reproduction 2009;138:309e17. [30] Taweechaipaisankul A, Jin JX, Lee S, Kim GA, Suh YH, Ahn MS, Park SJ, Lee BY, Lee BC. Improved early development of porcine cloned embryos by treatment with quisinostat, a potent histone deacetylase inhibitor. J Reprod Dev 2019;65:103e12. [31] Wen BQ, Li J, Li JJ, Tian SJ, Sun SC, Qi X, Cai WT, Chang QL. The histone deacetylase inhibitor Scriptaid improves in vitro developmental competence of ovine somatic cell nuclear transferred embryos. Theriogenology 2014;81: 332e9. [32] Wang LJ, Zhang H, Wang YS, Xu WB, Xiong XR, Li YY, Su JM, Hua S, Zhang Y. Scriptaid improves in vitro development and nuclear reprogramming of somatic cell nuclear transfer bovine embryos. Cell Reprogr 2011;13:431e9. [33] Matoba S, Liu Y, Lu F, Iwabuchi KA, Shen L, Inoue A, Zhang Y. Embryonic development following somatic cell nuclear transfer impeded by persisting histone methylation. Cell 2014;159:884e95. [34] Chung YG, Matoba S, Liu Y, Eum JH, Lu F, Jiang W, Lee JE, Sepilian V, Cha KY, Lee DR, Zhang Y. Histone demethylase expression enhances human somatic
Please cite this article as: Ogura A, How to improve mouse cloning, Theriogenology, https://doi.org/10.1016/j.theriogenology.2020.01.038
6
A. Ogura / Theriogenology xxx (xxxx) xxx
[35]
[36]
[37]
[38] [39]
[40] [41]
[42]
[43]
[44]
[45]
[46]
[47] [48]
[49]
[50]
cell nuclear transfer efficiency and promotes derivation of pluripotent stem cells. Cell Stem Cell 2015;17:758e66. Tachibana M, Amato P, Sparman M, Gutierrez NM, Tippner Hedges R, Ma H, Kang E, Fulati A, Lee HS, Sritanaudomchai H, Masterson K, Larson J, Eaton D, Sadler Fredd K, Battaglia D, Lee D, Wu D, Jensen J, Patton P, Gokhale S, Stouffer RL, Wolf D, Mitalipov S. Human embryonic stem cells derived by somatic cell nuclear transfer. Cell 2013;153:1228e38. Liu W, Liu X, Wang C, Gao Y, Gao R, Kou X, Zhao Y, Li J, Wu Y, Xiu W, Wang S, Yin J, Liu W, Cai T, Wang H, Zhang Y, Gao S. Identification of key factors conquering developmental arrest of somatic cell cloned embryos by combining embryo biopsy and single-cell sequencing. Cell Discov 2016;2: 16010. Inoue K, Kohda T, Sugimoto M, Sado T, Ogonuki N, Matoba S, Shiura H, Ikeda R, Mochida K, Fujii T, Sawai K, Otte AP, Tian XC, Yang X, Ishino F, Abe K, Ogura A. Impeding Xist expression from the active X chromosome improves mouse somatic cell nuclear transfer. Science 2010;330:496e9. Huynh KD, Lee JT. X-chromosome inactivation: a hypothesis linking ontogeny and phylogeny. Nat Rev Genet 2005;6:410e8. Oikawa M, Inoue K, Shiura H, Matoba S, Kamimura S, Hirose M, Mekada K, Yoshiki A, Tanaka S, Abe K, Ishino F, Ogura A. Understanding the X chromosome inactivation cycle in mice: a comprehensive view provided by nuclear transfer. Epigenetics 2014;9:204e11. Inoue A, Jiang L, Lu F, Zhang Y. Genomic imprinting of Xist by maternal H3K27me3. Genes Dev 2017;31:1927e32. Chiba H, Hirasawa R, Kaneda M, Amakawa Y, Li E, Sado T, Sasaki H. De novo DNA methylation independent establishment of maternal imprint on X chromosome in mouse oocytes. Genesis 2008;46:768e74. Matoba S, Inoue K, Kohda T, Sugimoto M, Mizutani E, Ogonuki N, Nakamura T, Abe K, Nakano T, Ishino F, Ogura A. RNAi-mediated knockdown of Xist can rescue the impaired postimplantation development of cloned mouse embryos. Proc Natl Acad Sci U S A 2011;108:20621e6. Oikawa M, Matoba S, Inoue K, Kamimura S, Hirose M, Ogonuki N, Shiura H, Sugimoto M, Abe K, Ishino F, Ogura A. RNAi-mediated knockdown of Xist does not rescue the impaired development of female cloned mouse embryos. J Reprod Dev 2013;59:231e7. Yang X, Wu X, Yang Y, Gu T, Hong L, Zheng E, Xu Z, Zeng F, Shi J, Zhou R, Cai G, Wu Z, Li Z. Improvement of developmental competence of cloned male pig embryos by short hairpin ribonucleic acid (shRNA) vector-based but not small interfering RNA (siRNA)-mediated RNA interference (RNAi) of Xist expression. J Reprod Dev 2019. https://doi.org/10.1262/jrd.2019e0. Matoba S, Wang H, Jiang L, Lu F, Iwabuchi KA, Wu X, Inoue K, Yang L, Press W, Lee JT, Ogura A, Shen L, Zhang Y. Loss of H3K27me3 imprinting in somatic cell nuclear transfer embryos disrupts post-implantation development. Cell Stem Cell 2018;23:343e54. e5. Yang X, Smith SL, Tian XC, Lewin HA, Renard JP, Wakayama T. Nuclear reprogramming of cloned embryos and its implications for therapeutic cloning. Nat Genet 2007;39:295e302. Wakayama T, Yanagimachi R. Cloning of male mice from adult tail-tip cells. Nat Genet 1999;22:127e8. Tanaka S, Oda M, Toyoshima Y, Wakayama T, Tanaka M, Yoshida N, Hattori N, Ohgane J, Yanagimachi R, Shiota K. Placentomegaly in cloned mouse concept caused by expansion of the spongiotrophoblast layer. Biol Reprod 2001;65: 1813e21. Wakisaka N, Inoue K, Ogonuki N, Miki H, Sekita Y, Hanaki K, Akatsuka A, Kaneko Ishino T, Ishino F, Ogura A. Ultrastructure of placental hyperplasia in mice: comparison of placental phenotypes with three different etiologies. Placenta 2008;29:753e9. Singh U, Fohn LE, Wakayama T, Ohgane J, Steinhoff C, Lipkowitz B, Schulz R, Orth A, Ropers HH, Behringer RR, Tanaka S, Shiota K, Yanagimachi R, Nuber UA, Fundele R. Different molecular mechanisms underlie placental overgrowth phenotypes caused by interspecies hybridization, cloning, and Esx1 mutation. Dev Dynam 2004;230:149e64.
[51] Okae H, Matoba S, Nagashima T, Mizutani E, Inoue K, Ogonuki N, Chiba H, Funayama R, Tanaka S, Yaegashi N, Nakayama K, Sasaki H, Ogura A, Arima T. RNA sequencing-based identification of aberrant imprinting in cloned mice. Hum Mol Genet 2014;23:992e1001. [52] Hirose M, Hada M, Kamimura S, Matoba S, Honda A, Motomura K, Ogonuki N, Shawki HH, Inoue K, Takahashi S, Ogura A. Aberrant imprinting in mouse trophoblast stem cells established from somatic cell nuclear transfer-derived embryos. Epigenetics 2018;13:693e703. [53] Itoh M, Yoshida Y, Nishida K, Narimatsu M, Hibi M, Hirano T. Role of Gab1 in heart, placenta, and skin development and growth factor- and cytokineinduced extracellular signal-regulated kinase mitogen-activated protein kinase activation. Mol Cell Biol 2000;20:3695e704. [54] Miri K, Latham K, Panning B, Zhong Z, Andersen A, Varmuza S. The imprinted polycomb group gene Sfmbt2 is required for trophoblast maintenance and placenta development. Development 2013;140:4480e9. [55] Matoba S, Nakamuta S, Miura K, Hirose M, Shiura H, Kohda T, Nakamuta N, Ogura A. Paternal knockout of Slc38a4/SNAT4 causes placental hypoplasia associated with intrauterine growth restriction in mice. Proc Natl Acad Sci U S A 2019;116:21047e53. [56] Inoue A, Jiang L, Lu F, Suzuki T, Zhang Y. Maternal H3K27me3 controls DNA methylation-independent imprinting. Nature 2017;547:419e24. [57] Inoue K, Hirose M, Inoue H, Hatanaka Y, Honda A, Hasegawa A, Mochida K, Ogura A. The rodent-specific microRNA cluster within the Sfmbt2 gene is imprinted and essential for placental development. Cell Rep 2017;19:949e56. [58] Wakisaka Saito N, Kohda T, Inoue K, Ogonuki N, Miki H, Hikichi T, Mizutani E, Wakayama T, Kaneko Ishino T, Ogura A, Ishino F. Chorioallantoic placenta defects in cloned mice. Biochem Biophys Res Commun 2006;349:106e14. [59] Hirasawa R, Matoba S, Inoue K, Ogura A. Somatic donor cell type correlates with embryonic, but not extra-embryonic, gene expression in postimplantation cloned embryos. PLoS One 2013;8:e76422. [60] Hossein MS, Jeong YW, Park SW, Kim JJ, Lee E, Ko KH, Kim HS, Kim YW, Hyun SH, Shin T, Hawthorne L, Hwang WS. Cloning Missy: obtaining multiple offspring of a specific canine genotype by somatic cell nuclear transfer. Clon Stem Cells 2009;11:123e30. [61] Yamagata K, Nagai K, Miyamoto H, Anzai M, Kato H, Miyamoto K, Kurosaka S, Azuma R, Kolodeznikov II, Protopopov AV, Plotnikov VV, Kobayashi H, Kawahara Miki R, Kono T, Uchida M, Shibata Y, Handa T, Kimura H, Hosoi Y, Mitani T, Matsumoto K, Iritani A. Signs of biological activities of 28,000-yearold mammoth nuclei in mouse oocytes visualized by live-cell imaging. Sci Rep 2019;9:4050. https://doi.org/10.1038/s41598-019-40546-1. [62] Kamimura S, Inoue K, Ogonuki N, Hirose M, Oikawa M, Yo M, Ohara O, Miyoshi H, Ogura A. Mouse cloning using a drop of peripheral blood. Biol Reprod 2013;24:1e6. [63] Galli C, Duchi R, Moor RM, Lazzari G. Mammalian leukocytes contain all the genetic information necessary for the development of a new individual. Cloning 1999;1:161e70. [64] Mizutani E, Torikai K, Wakayama S, Nagatomo H, Ohinata Y, Kishigami S, Wakayama T. Generation of cloned mice and nuclear transfer embryonic stem cell lines from urine-derived cells. Sci Rep 2016;6:23808. [65] Hochedlinger K, Jaenisch R. Monoclonal mice generated by nuclear transfer from mature B and T donor cells. Nature 2002;415:1035e8. [66] Kaminuma O, Katayama K, Inoue K, Saeki M, Nishimura T, Kitamura N, Shimo Y, Tofukuji S, Ishida S, Ogonuki N, Kamimura S, Oikawa M, Katoh S, Mori A, Shichijo M, Hiroi T, Ogura A. Hyper-reactive cloned mice generated by direct nuclear transfer of antigen-specific CD4(þ) T cells. EMBO Rep 2017;18: 885e93. [67] Inoue K, Ogonuki N, Mekada K, Yoshiki A, Sado T, Ogura A. Sex-reversed somatic cell cloning in the mouse. J Reprod Dev 2009;55:566e9. [68] Miyamoto K, Tajima Y, Yoshida K, Oikawa M, Azuma R, Allen GE, Tsujikawa T, Tsukaguchi T, Bradshaw CR, Jullien J, Yamagata K, Matsumoto K, Anzai M, Imai H, Gurdon JB, Yamada M. Reprogramming towards totipotency is greatly facilitated by synergistic effects of small molecules. Biol Open 2017;6:415e24.
Please cite this article as: Ogura A, How to improve mouse cloning, Theriogenology, https://doi.org/10.1016/j.theriogenology.2020.01.038
Contents lists available at ScienceDirect
Theriogenology journal homepage: www.theriojournal.com
How to improve mouse cloning Atsuo Ogura a, b, c, * a
RIKEN BioResource Research Center, Ibaraki, 305-0074, Japan Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki, 305-8572, Japan c RIKEN Cluster for Pioneering Research, Saitama, 351-0198, Japan b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 15 January 2020 Accepted 18 January 2020 Available online xxx
The mouse is the most extensively used mammalian laboratory species in biology and medicine because of the ready availability of a wide variety of defined genetic and gene-modified strains and abundant genetic information. Its small size and rapid generation turnover are also advantages compared with other experimental animals. Using these advantages, somatic cell nuclear transfer (SCNT) in mice has provided invaluable information on epigenetics related to SCNT technology and cloning, playing a leading role in relevant technical improvements. These improvements include treatment with histone deacetylase inhibitors, correction of Xist gene expression (controlling X chromosome inactivation), and removal of methylated histones from SCNT-generated embryos, which have proven to be effective for SCNT cloning of other species. However, even with the best combination of these treatments, the birth rate in cloned offspring is still lower than intracytoplasmic sperm injection (ICSI) or in vitro fertilization (IVF). One remaining issue associated with SCNT is placental enlargement (hyperplasia) found in late pregnancy, but this abnormality might not be a major cause for the low efficiency of SCNT because many SCNT-derived embryos die before their placentas start to enlarge at midgestation (early postimplantation stage). It is known that, at this stage, undifferentiated trophoblast cells in the extraembryonic tissue of SCNT-derived embryos fail to proliferate. Understanding the molecular mechanisms is essential for further technical improvements of mouse SCNT, which might also provide clues for technical breakthroughs in mammalian SCNT and cloning in general. © 2020 Elsevier Inc. All rights reserved.
Keywords: Genomic imprinting Mouse Oocyte Somatic cell nuclear transfer Zygotic gene activation
1. What does mouse SCNT tell us? Somatic cell nuclear transfer (SCNT) in mammals is the sole reproductive technology that can produce a genetic copy of an animal from a single donor somatic cell [1,2]. Although its applications are enormous in basic biology as well as industry and medicine, the birth rates of cloned animals have been generally much lower than those of other reproductive techniques such as intracytoplasmic sperm injection (ICSI) or in vitro fertilization (IVF) [3]. The low efficiency of cloning following SCNT can be attributed to either genetic or epigenetic causes. While the former causes might arise accidentally and randomly, the latter causesdat least in partdoccur inevitably and nonrandomly, mostly representing differences between the epigenomes of germ and somatic cells [4,5]. Therefore, for technical improvements of SCNT, the most rational approach is to identify the epigenetic
* RIKEN BioResource Research Center, Ibaraki, 305-0074, Japan. E-mail address: [email protected].
abnormalities that are found in all or the majority of embryos and/ or their placentas, and then seek for methodology to correct these epigenetic abnormalities [5]. An alternative way for improving SCNT is to identify the cell types and genotypes of donor cells that ensure higher cloning efficiencies. The laboratory mouse (Mus musculus domesticus) might provide the best model for these strategies thanks to the presence of genetically defined strains, the availability of a large amount of genetic information, and relatively easy generation of gene-modified animals. Wakayama et al. first produced cloned mice using cumulus cells from the hybrids of two inbred strains, C57BL/6 and DBA/2 (BDF1), and BDF1 oocytes [6]. Since then, this combination of donor cells and oocytes has been the standard for mouse cloning by SCNT, which enables comparison of cloning efficiencies wherever it is performed (Fig. 1). The high reproductive performance, short gestation period, and rapid generation turnover are also major advantages of the mouse as a laboratory species. Furthermore, the easy correction of a number of in vivo-matured oocytes of high quality is also an important advantage of the mouse for SCNT studies [7]; in other species such
https://doi.org/10.1016/j.theriogenology.2020.01.038 0093-691X/© 2020 Elsevier Inc. All rights reserved.
Please cite this article as: Ogura A, How to improve mouse cloning, Theriogenology, https://doi.org/10.1016/j.theriogenology.2020.01.038
2
A. Ogura / Theriogenology xxx (xxxx) xxx
Fig. 1. Improvements in mouse SCNT cloning. (A) Since the first report of successful mouse cloning by Wakayama et al. [6], the use of B6D2F1 cumulus cells as donors and B6D2F1 oocytes has been the standard for mouse cloning by SCNT. (B) This enables the reliable comparison of different technical improvements between different laboratories. This is one of the best merits of mouse SCNT [68].
as the pig, in vitro maturation of oocytes can significantly affect SCNT outcome [8,9]. Since the first report of successful mouse SCNT cloning by Wakayama et al. [6], we have focused for a long time on how to improve this approach. In the first 10 years, we assessed donor somatic cells from different cell types and different genotypes, and concluded ultimately that there was no relationship between cloning efficiency and the undifferentiated state of donor cells, and that the presence of the 129 strain genome significantly improved cloning efficiency [10] (Fig. 2). As a result, many mouse cloned offspring with a variety of cell types (e.g., NKT cells, hematopoietic stem cells, neural stem cells, and primordial germ cells) were born using the C57BL/6 129 F1 hybrid genotype [11e14]. It is also noteworthy that Wakayama’s group has successfully propagated many generations of cloned mice by serial SCNT using cumulus cells with the BDF1 129/Sv F1 genetic background [15]. The 129 strain is also known as that in which the first embryonic stem cell line was established [16,17]. These results have led us to assume that 129 mouse genome has an exceptionally high genomic plasticity, but we do not know the underlying molecular mechanisms. After a number of SCNT trials using recombinant inbred strains between C57BL6 and 129, we have narrowed down the genomic regions responsible for the genomic plasticity of the 129 strain into four separate regions located on chromosomes 2, 5, 8, and 19 [18]. Full understanding of these mechanisms will contribute to significant improvements in SCNT cloning as well as refinement of other genomic reprogramming-related technologies such as the generation of induced pluripotent cells. 2. Epigenetic characteristics of SCNT-generated mouse embryos The abnormal epigenetic characteristic first identified for SCNT-derived embryos was DNA hypermethylation in bovine preimplantation embryos [19]. That study showed that donor-type DNA methylation was maintained in a specific interspersed nuclear element sequence during preimplantation development. To overcome this problem, many studies have attempted to decrease the DNA methylation level of SCNT-derived embryos by treatment of donor cells or reconstructed embryos with DNA
methyltransferase (DNMT) inhibitors such as azacytidine. Although improved development into blastocysts were reported in some cases [20,21], this strategy did not lead to technical breakthroughs in SCNT probably because no or only minor effects on the birth rates have been reported. The first technical breakthrough in SCNT methodology was achieved in mouse cloning by using trichostatin A (TSA), a potent histone deacetylate inhibitor [22,23] (Fig. 1B). Interestingly, TSA exerts its best effect when it is administered to reconstructed embryos, but not to the donor cells before nuclear transfer. It is very probable that the synergistic effects of the loosened chromatin state induced by TSA and the maternal (ooplasmic) chromatin-modifying factors might be a key for success. Our comparative transcriptome analysis using TSAtreated SCNT-derived embryos, non-treated SCNT-derived embryos, and IVF-derived embryos revealed that the effects of TSA were not random, but specifically increased the expression levels of genes linked to zygotic gene activation (ZGA), which occurs at the 2-cell embryo stage in mice [24]. It is generally assumed that zygotic activation proceeds with de novo activation of transcription factors, which then activate another layer of genes encoding transcription factors. Indeed, we identified that one of the upstream ZGA genes, Spic, was activated in TSA-treated SCNT-derived embryos, but not in nontreated embryos. Interestingly, injection of mRNA for the Spic gene alone into SCNT-derived embryos resulted in a transcriptional profile resembling TSA-treated embryos produced by SCNT and IVF. The TSA treatment was proven to be effective for SCNT of other species such as pigs, bovines, and monkeys [25e27]. Similarly, other histone deacetylate inhibitors such as suberoylanilide hydroxamic acid (SAHA) or scriptaid are reported to improve development of cloned embryos in mice, followed by many other species [28e32]. Thanks to the recent advent of next generation sequence technology, RNA-sequencing (RNA-seq) has become available for the detailed transcriptome analysis of mammalian preimplantation embryos. Matoba et al. employed this technology for the analysis of SCNT- and IVF-derived mouse embryos and identified the inactive genomic regions specific for SCNT-derived embryos’ reprogramming-resistant regions (RRRs) [33]. Based on existing chromosome immunoprecipitation (ChIP)-sequencing data for mouse somatic cells, they found that RRRs are enriched for H3K9me3 and its removal by the ectopically expressed H3K9me3 demethylase Kdm4d greatly improved SCNT efficiency (Fig. 1B). Interestingly, a comparison of the effects of TSA and Kdm4d on SCNT-derived embryos indicated that both target the H3K9me3repressed genes in somatic cells, but Kdm4d treatment released their repressive state more extensively by expanding the active areas including centric/pericentric repeat sequences [33]. The Kdm4d treatment was found to improve the development of SCNT-derived embryos significantly in humans and cynomolgus monkeys, resulting in the production of nuclear transfer-derived embryonic stem cells (ntESCs) and cloned monkeys [27,34]. It is well known that SCNT-derived embryos in humans and primates are very hard to culture beyond the stage of ZGAdaround the 16cell stage in these speciesdand ntESCs can only be established at low efficiency [35]. These studies revealed that the major reprogramming barrier in these species is H3K9me3 derived from the donor cell genome. For further identification of reprogramming barriers in a stage-specific manner, Liu et al. combined embryo biopsy and single-cell sequencing for SCNT-derived mouse embryos. They found that inactivation of Kdm4b and Kdm5b functioned as barriers for the 2-cell and 4-cell arrest stages of SCNT-derived embryos, respectively. Indeed, coinjection of mRNAs for Kdm4b and Kdm5b could restore the transcriptional profiles of SCNT-derived embryos and improve the production of cloned mice [36].
Please cite this article as: Ogura A, How to improve mouse cloning, Theriogenology, https://doi.org/10.1016/j.theriogenology.2020.01.038
A. Ogura / Theriogenology xxx (xxxx) xxx
3
Fig. 2. The presence of the 129 strain genome significantly increased the cloning efficiency. (A) B6 129 F1 Sertoli cells gave the best birth rate (>10%) without TSA. Two-way analysis of variance revealed that both the cell type (cumulus Sertoli) and the genotype had significant effects on the birth rate, and that there was a significant interaction between them, indicating that the combination of these two factors may affect the SCNT outcome. (B) The 129 genome enhances the genomic reprogramming of hematopoietic stem cells. More than half of the cloned embryos developed into blastocysts expressing EGFP-Oct4. Data are from Refs. [10,12].
Another transcriptome analysis using SCNT-derived mouse blastocysts revealed that SCNT-specific downregulation predominantly occurred in X-linked genes [37]. This was caused by ectopic expression of the Xist gene, which is responsible for X chromosome inactivation in mammalian cells [38]. In female preimplantation embryos in mice, but not humans and rabbits, Xist is exclusively expressed from the paternal allele so that the dosage of X-linked genes in female embryos (XX) is maintained at the same level as in male embryos (XY). Our large-scale nuclear transfer experiments using somatic cells and germ cells at different developmental stages suggested that Xist is expressed at the 4-cell stage as a default and that this is repressed in the maternal allele by imprinting established during the last stage of oogenesis [39]. Later, it was confirmed that this imprint was dependent on H3K27me3 [40], consistent with the previous notion thatdunlike other canonical imprinting systemsdthis Xist imprint did not depend on DNA methylation [41]. As it is erased in the embryonic linage after implantation, somatic cells have lost this memory. Therefore, cloned embryos derived from somatic cells have no Xist-repressing imprint and Xist is expressed in both maternal and paternal alleles, leading to the aberrant repression of X-linked genes. Surprisingly, correction of the Xist expression pattern in SCNT-derived embryos by Xist gene knockout or knockdown resulted in a nearly 10-fold increase in the birth rates of clones [37,42] (Fig. 1B). However, the knockdown strategy was effective only in male SCNT-derived embryos because of the inability of allele-specific repression of Xist by conventional siRNA injection [43]. In pigs, Xist knockdown also improved the developmental competence of male SCNT-derived embryos, although a longer blocking effect on Xist by injection with shRNA plasmids, rather than siRNA injection, was necessary [44]. It is important to note that correction of the Xist expression pattern is effective in the rescue of early postimplantation embryos following SCNT [42], in contrast to the predominant improvement of preimplantation SCNT-derived embryos by Kdm4d treatment [33]. Consistent with this, maternal Xist knockout of donor cells and Kdm4d mRNA injection into reconstructed embryos had a synergistic effect and their combination increased the birth rates to as high as 18.7% and 23.5% with cumulus and Sertoli cells, used as donors, respectively [45] (Fig. 1B).
3. Abnormal placental development following mouse SCNT The placenta is the organ that facilitates the maternalefetal exchanges of gases, nutrients, and all other supplies necessary for fetal growth, while separating the fetal and maternal circulations. The placenta has attracted special attention from cloning researchers because SCNT is often associated with morphological abnormalities of placentas even in cases of normal delivery of cloned offspring [46]. In mouse SCNT, it is well known that placental enlargement (placentomegaly) inevitably occurs during the late gestation period [47,48] (Fig. 3A and B). This enlargement is predominantly caused by an expansion of the spongiotrophoblast (ST) layer (the junctional zone) that includes swollen ST cells with enlarged endoplasmic reticulum and an increased number of glycogen storage cells [48,49] (Fig. 3B and C). As a very similar placental phonotype also appears in interspecies crosses (e.g., M. musculus M. spretus) and Esx1 knockout mice, Fundele et al. attempted to identify the causative genes by comparative transcriptome analysis using enlarged placentas from these three different sources including SCNT-derived embryos and from normal control placentas derived by natural mating of laboratory mice [50]. However, only one gene of known function (Ramp2) and one gene of unknown function were found common to all three types of enlarged placentas [50]. It is conceivable that, because the histology of enlarged placentas is much different from that of control placentas, differentially expressed genes in each experimental group might have simply reflected the results of aberrant placental histology. As placental enlargement occurs in most clones, there should be some primary key mechanism(s) that are always associated with mouse SCNT. As far as we and others have observed, the technical breakthroughs so far achieved, such as corrections of Xist or H3K9me3-repressed genes, have never ameliorated the aberrant placental phenotype [33,37]. Therefore, we should seek for other epigenetic errors that might impair placental, rather than fetal, development. In this context, placentaspecific imprinted genes might be probable candidates. Previously, we have identified loss of imprinting (LOI) of three placentaspecific imprinted genes, Gab1, Sfmbt2, and Slc38a4, in SCNTderived placentas [51]. This was further confirmed using SCNT-
Please cite this article as: Ogura A, How to improve mouse cloning, Theriogenology, https://doi.org/10.1016/j.theriogenology.2020.01.038
4
A. Ogura / Theriogenology xxx (xxxx) xxx
Fig. 3. Placental enlargement associated with mouse SCNT. (A and B) This placental phenotype is characterized by the enlarged spongiotrophoblast (ST) layer, an irregular spongiotrophoblastelabyrinthine (LB) cell boundary and proliferation of glycogen-rich cells. (C) The enlargement of the ST layer is causeddat least in partdby cell hypertrophy with expanded rough endoplasmic reticulum (ER; arrows).
derived trophoblast stem cells [52]. LOI leads to biallelic expression of these genes, which might have caused placental enlargement, because it was reported that these genes can positively regulate placental development based on observations of mutant forms of these genes [53e55]. Therefore, we employed a maternal gene knockout strategy to recover a normal paternal expression, as we did for the rescue of ectopic Xist expression in cloned embryos. However, the maternal knockout of either of the genes did not decrease the placental size at term following SCNT. These placentaspecific, paternally expressed imprinted genes are reported to be regulated by a histone mark, H3K27me3 [56]. We further examined the possible involvement of other H3K27me3-regulated imprinted genes in the enlargement of SCNT-derived placentas and finally identified a set of downstream genes responsible for this phenotype [57]. It will be interesting to examine whether the expressions of these genes are also altered in interspecies hybrids or Esx1 gene knockout placentas. Thus, the major cause for the enlargement of SCNT-derived placentas has been identified, but we also found that this placental phenotype does not significantly affect the development of SCNT-derived embryos. Indeed, the stage at which most SCNT-derived mouse embryos die is the early postimplantation period without placental enlargement (embryo days, E6.5eE9.5). During this stage, paradoxically, the SCNT-derived extraembryonic tissues show poor development because of the low proliferating ability of undifferentiated trophoblast cells that express Cdx2, Esrrb, and Eomes [58,59]. This early placental anomaly might be the next target for further improvement of mouse SCNT. 4. Potential applications of SCNT One of the important purposes of mammalian SCNT is the production of genetic copies from valuable animals. It might even be possible to produce cloned offspring from dead individuals or resurrect the genotypes of extinct animals. In 2007, the world’s first
clone of a family dog, Missy, was born using her cryopreserved somatic cells [60]. Cells recovered from the 28,000-year-old frozen remains of a woolly mammoth showed spindle assembly, histone incorporation, and partial nuclear formation, although the nuclei were too damaged to go further [61]. In laboratory mice, duplication of genetically unidentified mutants might prove practical, especially when the phenotype is dependent on the unknown genetic background. It is desirable for donor cells that are ready for use to be repeatedly collected without damaging the donor animals. For this purpose, we examined the possibility of using (nucleated) leukocytes collected from a drop of peripheral blood as SCNT donor cells. The leukocyte suspension was prepared by lysing the erythrocytes. Using fluorescence-activated cell sorting, we found that most nucleated cells >8 mm in diameter were granulocytes or monocytes. We confirmed that both putative granulocytes/monocytes and lymphocytes could be used for cloning mice by SCNT [62]. Because the use of lymphocytes will result in the birth of offspring with DNA rearrangements, we applied granulocyte/monocyte cloning to two genetically modified strains and two recombinant inbred strains, and offspring were obtained from all four strains tested [62]. This strategy could be applied to the rescue of infertile founder animals or a “last-of-line” animal possessing invaluable genetic resources. A calf was also born from a leukocyte using a serial cloning method, in which somatically cloned blastomeres (compacting morulae) were subjected to a second round of nuclear transfer [63]. Later, Wakayama’s group reported that sediment cells in urine can be used for the production of cloned mice and ntESCs [64]. This should be one of the most invasive ways to make genetic copies of animals by SCNT. As mentioned above, the use of lymphocytes as donor cells results in the production of cloned animals carrying rearranged DNA in their whole body. Hochedlinger and Jaenisch produced “monoclonal mice” derived from mature B- and T-cells via ntESC and chimera generation [65] and Inoue et al. generated NKT cell-
Please cite this article as: Ogura A, How to improve mouse cloning, Theriogenology, https://doi.org/10.1016/j.theriogenology.2020.01.038
A. Ogura / Theriogenology xxx (xxxx) xxx
derived cloned mice by direct SCNT [11]. In either case, the offspring carried the expected DNA rearrangements. Taking advantage of this feature, we generated cloned mice that carry endogenously rearranged T-cell receptor (TCR) genes from CD4þ T cells specific for antigens, mite antigens, and ovalbumin, which had been administered to the donor animals [66]. The pre-rearranged TCR alleles of the clones were transmitted to the offspring, allowing us to establish a set of mouse lines. They showed chronic-type allergic phenotypes, and bronchial and nasal inflammation upon local administration of the corresponding antigens [66]. These mouse lines are available from our center for research use (https:// mus.brc.riken.jp/en/). Thus, SCNT can be used for the generation of new mouse strains for research. One of the biggest technical challenges inherent to SCNT is the inflexibility of the sex of the offspring. Cloning male cells inevitably results in the birth of male, not female neonates, and vice versa. This sex irreversibility might become an important issue, especially when sexual breeding must be resumed for subsequent propagation, for example in projects for the resurrection of extinct species or the rescue of endangered species. While we were producing cloned mice using Sertoli cells as nuclear donors, one female mouse was born accidentally. This “male-derived female” clone grew into a normal adult and produced offspring by natural mating with a littermate [67]. Chromosomal analysis revealed that the female clone had a 39,X karyotype (XO or Turner syndrome), indicating that the Y chromosome had been deleted in the donor cell or at some early step during the SCNT procedure. This finding suggests the possibility of resuming sexual reproduction after cloning a single male animal, as XO females could be fertile, as in the case of this mouse. In conclusion, mouse SCNT may provide us with invaluable information on mammalian developmental epigenetics as well as experimental models for biomedical researches. So far, we have successfully cloned all types of somatic cells we tested, provided they had a normal chromosomal constitution and normal genomic imprinting. Thus, although the differentiation-associated memories are highly variable, they might be easily reprogramed at nuclear transfer. By contrast, genome-wide somatic epigenetic marks imposed at implantation (such as repressive histone marks) seem to be more rigid, but their number may be limited. Therefore, we might be able to achieve high-yield SCNT cloning outcomes by targeting fewer epigenetic errors than originally anticipated. Acknowledgment A part of this study was supported by Grants-in-Aid from the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) (Nos. 25112009 and 19H05758) and Epigenome Manipulation Project of the All-RIKEN Projects. References [1] Gurdon JB. Nuclear transplantation, the conservation of the genome, and prospects for cell replacement. FEBS J 2017;284:211e7. [2] Miyamoto K. Various nuclear reprogramming systems using egg and oocyte materials. J Reprod Dev 2019;65:203e8. [3] Loi P, Iuso D, Czernik M, Ogura A. A new, dynamic era for somatic cell nuclear transfer? Trends Biotechnol 2016;34:791e7. [4] Ogura A, Inoue K, Wakayama T. Recent advancements in cloning by somatic cell nuclear transfer. Philos Trans R Soc Lond B Biol Sci 2013;368: 20110329. [5] Matoba S, Zhang Y. Somatic cell nuclear transfer reprogramming: mechanisms and applications. Cell Stem Cell 2018;23:471e85. [6] Wakayama T, Perry ACF, Zuccotti M, Johnson KR, Yanagimachi R. Full-term development of mice from enucleated oocytes injected with cumulus cell nuclei. Nature 1998;394:369e74. [7] Hasegawa A, Mochida K, Inoue H, Noda Y, Endo T, Watanabe G, Ogura A. Highyield superovulation in adult mice by anti-inhibin serum treatment combined with estrous cycle synchronization. Biol Reprod 2016;94:21.
5
[8] Kim MJ, Oh HJ, Choi YB, Lee S, Setyawan EMN, Lee SH, Lee SH, Hur TY, Lee BC. Suberoylanilide hydroxamic acid during in vitro culture improves development of dog-pig interspecies cloned embryos but not dog cloned embryos. J Reprod Dev 2018;64:277e82. [9] Wang X, Zhu X, Liang X, Xu H, Liao Y, Lu K, Lu S. Effects of resveratrol on in vitro maturation of porcine oocytes and subsequent early embryonic development following somatic cell nuclear transfer. Reprod Domest Anim 2019;54:1195e205. [10] Inoue K, Ogonuki N, Mochida K, Yamamoto Y, Takano K, Kohda T, Ishino F, Ogura A. Effects of donor cell type and genotype on the efficiency of mouse somatic cell cloning. Biol Reprod 2003;69:1394e400. [11] Inoue K, Wakao H, Ogonuki N, Miki H, Seino K, Nambu-Wakao R, Noda S, Miyoshi H, Koseki H, Taniguchi M, Ogura A. Generation of cloned mice by direct nuclear transfer from natural killer T cells. Curr Biol 2005;15:1114e8. [12] Inoue K, Ogonuki N, Miki H, Hirose M, Noda S, Kim JM, Aoki F, Miyoshi H, Ogura A. Inefficient reprogramming of the hematopoietic stem cell genome following nuclear transfer. J Cell Sci 2006;119:1985e91. [13] Inoue K, Noda S, Ogonuki N, Miki H, Inoue S, Katayama K, Mekada K, Miyoshi H, Ogura A. Differential developmental ability of embryos cloned from tissue-specific stem cells. Stem Cells 2007;25:1279e85. [14] Miki H, Inoue K, Kohda T, Honda A, Ogonuki N, Yuzuriha M, Mise N, Matsui Y, Baba T, Abe K, Ishino F, Ogura A. Birth of mice produced by germ cell nuclear transfer. Genesis 2005;41:81e6. [15] Wakayama S, Kohda T, Obokata H, Tokoro M, Li C, Terashita Y, Mizutani E, Nguyen VT, Kishigami S, Ishino F, Wakayama T. Successful serial recloning in the mouse over multiple generations. Cell Stem Cell 2013;12:293e7. [16] Evans MJ, Kaufman MH. Establishment in culture of pluripotential cells from mouse embryos. Nature 1981;292:154e6. [17] Martin GR. Isolation of a pluripotent cell line from early mouse embryos cultured in medium conditioned by teratocarcinoma stem cells. Proc Natl Acad Sci U S A 1981;78:7634e8. [18] Inoue K, Ogura A. In quest of genomic treasure. J Reprod Dev 2015;61:489e93. [19] Kang YK, Koo DB, Park JS, Choi YH, Chung AS, Lee KK, Han YM. Aberrant methylation of donor genome in cloned bovine embryos. Nat Genet 2001;28: 173e7. [20] Enright BP, Kubota C, Yang X, Tian XC. Epigenetic characteristics and development of embryos cloned from donor cells treated by trichostatin A or 5-aza20 -deoxycytidine. Biol Reprod 2003;69:896e901. [21] Enright BP, Sung LY, Chang CC, Yang X, Tian XC. Methylation and acetylation characteristics of cloned bovine embryos from donor cells treated with 5-aza20 -deoxycytidine. Biol Reprod 2005;72:944e8. [22] Kishigami S, Mizutani E, Ohta H, Hikichi T, Thuan NV, Wakayama S, Bui HT, Wakayama T. Significant improvement of mouse cloning technique by treatment with trichostatin A after somatic nuclear transfer. Biochem Biophys Res Commun 2006;340:183e9. [23] Rybouchkin A, Kato Y, Tsunoda Y. Role of histone acetylation in reprogramming of somatic nuclei following nuclear transfer. Biol Reprod 2006;74: 1083e9. [24] Inoue K, Oikawa M, Kamimura S, Ogonuki N, Nakamura T, Nakano T, Abe K, Ogura A. Trichostatin A specifically improves the aberrant expression of transcription factor genes in embryos produced by somatic cell nuclear transfer. Sci Rep 2015;5:10127. https://doi.org/10.1038/srep10127. [25] Li J, Svarcova O, Villemoes K, Kragh PM, Schmidt M, Bogh IB, Zhang Y, Du Y, Lin L, Purup S, Xue Q, Bolund L, Yang H, Maddox Hyttel P, Vajta G. High in vitro development after somatic cell nuclear transfer and trichostatin A treatment of reconstructed porcine embryos. Theriogenology 2008;70:800e8. [26] Iager AE, Ragina NP, Ross PJ, Beyhan Z, Cunniff K, Rodriguez RM, Cibelli JB. Trichostatin A improves histone acetylation in bovine somatic cell nuclear transfer early embryos. Clon Stem Cells 2008;10:371e9. [27] Liu Z, Cai Y, Wang Y, Nie Y, Zhang C, Xu Y, Zhang X, Lu Y, Wang Z, Poo M, Sun Q. Cloning of macaque monkeys by somatic cell nuclear transfer. Cell 2018;172:881e7. e7. [28] Ono T, Li C, Mizutani E, Terashita Y, Yamagata K, Wakayama T. Inhibition of class IIb histone deacetylase significantly improves cloning efficiency in mice. Biol Reprod 2010;83:929e37. [29] Van Thuan N, Bui HT, Kim JH, Hikichi T, Wakayama S, Kishigami S, Mizutani E, Wakayama T. The histone deacetylase inhibitor scriptaid enhances nascent mRNA production and rescues full-term development in cloned inbred mice. Reproduction 2009;138:309e17. [30] Taweechaipaisankul A, Jin JX, Lee S, Kim GA, Suh YH, Ahn MS, Park SJ, Lee BY, Lee BC. Improved early development of porcine cloned embryos by treatment with quisinostat, a potent histone deacetylase inhibitor. J Reprod Dev 2019;65:103e12. [31] Wen BQ, Li J, Li JJ, Tian SJ, Sun SC, Qi X, Cai WT, Chang QL. The histone deacetylase inhibitor Scriptaid improves in vitro developmental competence of ovine somatic cell nuclear transferred embryos. Theriogenology 2014;81: 332e9. [32] Wang LJ, Zhang H, Wang YS, Xu WB, Xiong XR, Li YY, Su JM, Hua S, Zhang Y. Scriptaid improves in vitro development and nuclear reprogramming of somatic cell nuclear transfer bovine embryos. Cell Reprogr 2011;13:431e9. [33] Matoba S, Liu Y, Lu F, Iwabuchi KA, Shen L, Inoue A, Zhang Y. Embryonic development following somatic cell nuclear transfer impeded by persisting histone methylation. Cell 2014;159:884e95. [34] Chung YG, Matoba S, Liu Y, Eum JH, Lu F, Jiang W, Lee JE, Sepilian V, Cha KY, Lee DR, Zhang Y. Histone demethylase expression enhances human somatic
Please cite this article as: Ogura A, How to improve mouse cloning, Theriogenology, https://doi.org/10.1016/j.theriogenology.2020.01.038
6
A. Ogura / Theriogenology xxx (xxxx) xxx
[35]
[36]
[37]
[38] [39]
[40] [41]
[42]
[43]
[44]
[45]
[46]
[47] [48]
[49]
[50]
cell nuclear transfer efficiency and promotes derivation of pluripotent stem cells. Cell Stem Cell 2015;17:758e66. Tachibana M, Amato P, Sparman M, Gutierrez NM, Tippner Hedges R, Ma H, Kang E, Fulati A, Lee HS, Sritanaudomchai H, Masterson K, Larson J, Eaton D, Sadler Fredd K, Battaglia D, Lee D, Wu D, Jensen J, Patton P, Gokhale S, Stouffer RL, Wolf D, Mitalipov S. Human embryonic stem cells derived by somatic cell nuclear transfer. Cell 2013;153:1228e38. Liu W, Liu X, Wang C, Gao Y, Gao R, Kou X, Zhao Y, Li J, Wu Y, Xiu W, Wang S, Yin J, Liu W, Cai T, Wang H, Zhang Y, Gao S. Identification of key factors conquering developmental arrest of somatic cell cloned embryos by combining embryo biopsy and single-cell sequencing. Cell Discov 2016;2: 16010. Inoue K, Kohda T, Sugimoto M, Sado T, Ogonuki N, Matoba S, Shiura H, Ikeda R, Mochida K, Fujii T, Sawai K, Otte AP, Tian XC, Yang X, Ishino F, Abe K, Ogura A. Impeding Xist expression from the active X chromosome improves mouse somatic cell nuclear transfer. Science 2010;330:496e9. Huynh KD, Lee JT. X-chromosome inactivation: a hypothesis linking ontogeny and phylogeny. Nat Rev Genet 2005;6:410e8. Oikawa M, Inoue K, Shiura H, Matoba S, Kamimura S, Hirose M, Mekada K, Yoshiki A, Tanaka S, Abe K, Ishino F, Ogura A. Understanding the X chromosome inactivation cycle in mice: a comprehensive view provided by nuclear transfer. Epigenetics 2014;9:204e11. Inoue A, Jiang L, Lu F, Zhang Y. Genomic imprinting of Xist by maternal H3K27me3. Genes Dev 2017;31:1927e32. Chiba H, Hirasawa R, Kaneda M, Amakawa Y, Li E, Sado T, Sasaki H. De novo DNA methylation independent establishment of maternal imprint on X chromosome in mouse oocytes. Genesis 2008;46:768e74. Matoba S, Inoue K, Kohda T, Sugimoto M, Mizutani E, Ogonuki N, Nakamura T, Abe K, Nakano T, Ishino F, Ogura A. RNAi-mediated knockdown of Xist can rescue the impaired postimplantation development of cloned mouse embryos. Proc Natl Acad Sci U S A 2011;108:20621e6. Oikawa M, Matoba S, Inoue K, Kamimura S, Hirose M, Ogonuki N, Shiura H, Sugimoto M, Abe K, Ishino F, Ogura A. RNAi-mediated knockdown of Xist does not rescue the impaired development of female cloned mouse embryos. J Reprod Dev 2013;59:231e7. Yang X, Wu X, Yang Y, Gu T, Hong L, Zheng E, Xu Z, Zeng F, Shi J, Zhou R, Cai G, Wu Z, Li Z. Improvement of developmental competence of cloned male pig embryos by short hairpin ribonucleic acid (shRNA) vector-based but not small interfering RNA (siRNA)-mediated RNA interference (RNAi) of Xist expression. J Reprod Dev 2019. https://doi.org/10.1262/jrd.2019e0. Matoba S, Wang H, Jiang L, Lu F, Iwabuchi KA, Wu X, Inoue K, Yang L, Press W, Lee JT, Ogura A, Shen L, Zhang Y. Loss of H3K27me3 imprinting in somatic cell nuclear transfer embryos disrupts post-implantation development. Cell Stem Cell 2018;23:343e54. e5. Yang X, Smith SL, Tian XC, Lewin HA, Renard JP, Wakayama T. Nuclear reprogramming of cloned embryos and its implications for therapeutic cloning. Nat Genet 2007;39:295e302. Wakayama T, Yanagimachi R. Cloning of male mice from adult tail-tip cells. Nat Genet 1999;22:127e8. Tanaka S, Oda M, Toyoshima Y, Wakayama T, Tanaka M, Yoshida N, Hattori N, Ohgane J, Yanagimachi R, Shiota K. Placentomegaly in cloned mouse concept caused by expansion of the spongiotrophoblast layer. Biol Reprod 2001;65: 1813e21. Wakisaka N, Inoue K, Ogonuki N, Miki H, Sekita Y, Hanaki K, Akatsuka A, Kaneko Ishino T, Ishino F, Ogura A. Ultrastructure of placental hyperplasia in mice: comparison of placental phenotypes with three different etiologies. Placenta 2008;29:753e9. Singh U, Fohn LE, Wakayama T, Ohgane J, Steinhoff C, Lipkowitz B, Schulz R, Orth A, Ropers HH, Behringer RR, Tanaka S, Shiota K, Yanagimachi R, Nuber UA, Fundele R. Different molecular mechanisms underlie placental overgrowth phenotypes caused by interspecies hybridization, cloning, and Esx1 mutation. Dev Dynam 2004;230:149e64.
[51] Okae H, Matoba S, Nagashima T, Mizutani E, Inoue K, Ogonuki N, Chiba H, Funayama R, Tanaka S, Yaegashi N, Nakayama K, Sasaki H, Ogura A, Arima T. RNA sequencing-based identification of aberrant imprinting in cloned mice. Hum Mol Genet 2014;23:992e1001. [52] Hirose M, Hada M, Kamimura S, Matoba S, Honda A, Motomura K, Ogonuki N, Shawki HH, Inoue K, Takahashi S, Ogura A. Aberrant imprinting in mouse trophoblast stem cells established from somatic cell nuclear transfer-derived embryos. Epigenetics 2018;13:693e703. [53] Itoh M, Yoshida Y, Nishida K, Narimatsu M, Hibi M, Hirano T. Role of Gab1 in heart, placenta, and skin development and growth factor- and cytokineinduced extracellular signal-regulated kinase mitogen-activated protein kinase activation. Mol Cell Biol 2000;20:3695e704. [54] Miri K, Latham K, Panning B, Zhong Z, Andersen A, Varmuza S. The imprinted polycomb group gene Sfmbt2 is required for trophoblast maintenance and placenta development. Development 2013;140:4480e9. [55] Matoba S, Nakamuta S, Miura K, Hirose M, Shiura H, Kohda T, Nakamuta N, Ogura A. Paternal knockout of Slc38a4/SNAT4 causes placental hypoplasia associated with intrauterine growth restriction in mice. Proc Natl Acad Sci U S A 2019;116:21047e53. [56] Inoue A, Jiang L, Lu F, Suzuki T, Zhang Y. Maternal H3K27me3 controls DNA methylation-independent imprinting. Nature 2017;547:419e24. [57] Inoue K, Hirose M, Inoue H, Hatanaka Y, Honda A, Hasegawa A, Mochida K, Ogura A. The rodent-specific microRNA cluster within the Sfmbt2 gene is imprinted and essential for placental development. Cell Rep 2017;19:949e56. [58] Wakisaka Saito N, Kohda T, Inoue K, Ogonuki N, Miki H, Hikichi T, Mizutani E, Wakayama T, Kaneko Ishino T, Ogura A, Ishino F. Chorioallantoic placenta defects in cloned mice. Biochem Biophys Res Commun 2006;349:106e14. [59] Hirasawa R, Matoba S, Inoue K, Ogura A. Somatic donor cell type correlates with embryonic, but not extra-embryonic, gene expression in postimplantation cloned embryos. PLoS One 2013;8:e76422. [60] Hossein MS, Jeong YW, Park SW, Kim JJ, Lee E, Ko KH, Kim HS, Kim YW, Hyun SH, Shin T, Hawthorne L, Hwang WS. Cloning Missy: obtaining multiple offspring of a specific canine genotype by somatic cell nuclear transfer. Clon Stem Cells 2009;11:123e30. [61] Yamagata K, Nagai K, Miyamoto H, Anzai M, Kato H, Miyamoto K, Kurosaka S, Azuma R, Kolodeznikov II, Protopopov AV, Plotnikov VV, Kobayashi H, Kawahara Miki R, Kono T, Uchida M, Shibata Y, Handa T, Kimura H, Hosoi Y, Mitani T, Matsumoto K, Iritani A. Signs of biological activities of 28,000-yearold mammoth nuclei in mouse oocytes visualized by live-cell imaging. Sci Rep 2019;9:4050. https://doi.org/10.1038/s41598-019-40546-1. [62] Kamimura S, Inoue K, Ogonuki N, Hirose M, Oikawa M, Yo M, Ohara O, Miyoshi H, Ogura A. Mouse cloning using a drop of peripheral blood. Biol Reprod 2013;24:1e6. [63] Galli C, Duchi R, Moor RM, Lazzari G. Mammalian leukocytes contain all the genetic information necessary for the development of a new individual. Cloning 1999;1:161e70. [64] Mizutani E, Torikai K, Wakayama S, Nagatomo H, Ohinata Y, Kishigami S, Wakayama T. Generation of cloned mice and nuclear transfer embryonic stem cell lines from urine-derived cells. Sci Rep 2016;6:23808. [65] Hochedlinger K, Jaenisch R. Monoclonal mice generated by nuclear transfer from mature B and T donor cells. Nature 2002;415:1035e8. [66] Kaminuma O, Katayama K, Inoue K, Saeki M, Nishimura T, Kitamura N, Shimo Y, Tofukuji S, Ishida S, Ogonuki N, Kamimura S, Oikawa M, Katoh S, Mori A, Shichijo M, Hiroi T, Ogura A. Hyper-reactive cloned mice generated by direct nuclear transfer of antigen-specific CD4(þ) T cells. EMBO Rep 2017;18: 885e93. [67] Inoue K, Ogonuki N, Mekada K, Yoshiki A, Sado T, Ogura A. Sex-reversed somatic cell cloning in the mouse. J Reprod Dev 2009;55:566e9. [68] Miyamoto K, Tajima Y, Yoshida K, Oikawa M, Azuma R, Allen GE, Tsujikawa T, Tsukaguchi T, Bradshaw CR, Jullien J, Yamagata K, Matsumoto K, Anzai M, Imai H, Gurdon JB, Yamada M. Reprogramming towards totipotency is greatly facilitated by synergistic effects of small molecules. Biol Open 2017;6:415e24.
Please cite this article as: Ogura A, How to improve mouse cloning, Theriogenology, https://doi.org/10.1016/j.theriogenology.2020.01.038