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Inherited 15q24 microdeletion syndrome in twins and their father with phenotypic variability
European Journal of Medical Genetics xxx (2014) 1e5
Contents lists available at ScienceDirect
European Journal of Medical Genetics journal homepage: http://www.elsevier.com/locate/ejmg
Clinical report
Inherited 15q24 microdeletion syndrome in twins and their father with phenotypic variability Lena Samuelsson a, Theofanis Zagoras a, Maria Hafström b, c, d, * a
Department of Clinical Genetics, Sahlgrenska University Hospital, Sweden Department of Pediatrics, Institute of Clinical Sciences, The Queen Silvia Children’s Hospital, University of Gothenburg, Göteborg, Sweden c Department of Paediatrics, St. Olavs Hospital, Norway d Department of Laboratory Medicine, Children’s and Women’s Health, Norwegian University of Science and Technology, Trondheim, Norway b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 1 June 2014 Accepted 1 December 2014 Available online xxx
Background: Deletions including chromosome 15q24 have been delineated in recent years as a separate syndrome with phenotypic variability. Here we report a familial 15q24 deletion and further contribute to the phenotypic description of this syndrome. Methods: Molecular karyotyping and description of the phenotype of three patients in the same family with a 15q24 deletion. Results: Parental transmission of the 15q24 deletion syndrome is described in the same family. The affected, the father and his twin offspring, all exhibit the typical facial features, signs and symptoms consistent with the syndromic phenotype. A distinct phenotypic variability is nevertheless noted although they all share the same deletion. Conclusions: These three patients are to our knowledge the first described cases of 15q24 syndrome in the same family. Urogenital malformations have previously been described as a part of this syndrome. Our adult male patient exhibits no such malformations but has a documented reduced fertility. This fact points to other factors such as haploinsufficiency of one and/or further genes on 15q24 as being responsible for the infertility. Array analysis could be considered as a first hand analysis in the investigation of cases of infertility and intellectual deficiency in adults in analogy to the existing consensus regarding cases of intellectual deficiency in children. Ó 2014 Elsevier Masson SAS. All rights reserved.
Keywords: Chromosome deletion Intellectual disability Chromosome disorders Chromosomes human pair 15 Microarray analysis
1. Introduction The establishment of array-based molecular karyotyping has in recent years led to the discovery and precise delineation of copy number variants and microdeletion/duplication syndromes that have previously been unknown. Deletions including 15q24 were first described a few years ago [Sharp et al., 2007]. To date, more than 30 such cases have been reported in the literature [Andrieux et al., 2009; El-Hattab et al., 2009, 2010; IS et al., 2011; Klopocki et al., 2008; Marshall et al., 2008; Masurel-Paulet et al., 2009; McInnes et al., 2010; Mefford et al., 2012; Sharp et al., 2007; Van Esch et al., 2009]. The syndrome is associated with intellectual disability, characteristic
* Corresponding author. Department of Pediatrics, Institute of Clinical Sciences, The Queen Silvia Children’s Hospital, University of Gothenburg, S-416 85 Göteborg, Sweden. Tel.: þ46 702 806269; fax: þ46 31 3434316. E-mail address: [email protected] (M. Hafström).
facial features such as long face, hypertelorism and epicanthal folds as well as growth retardation, genital anomalies and skeletal deformities. Most of the 15q24 deletions’ breakpoints are located in one of five blocks of segmental duplications (SD), commonly referred to as SD block 15q24 A, B, C, D and E [ElHattab et al., 2009]. A smallest region of overlap (SRO) has been delineated and encompasses an approximately 1.2 Mb region between 15q24B and 15q24C since the majority of patients have deletions including this region [Andrieux et al., 2009; IS et al., 2011; Magoulas and El-Hattab, 2012; McInnes et al., 2010; Mefford et al., 2012]. In addition, at least two patients have been reported that have a deletion completely outside the region between block B and block C [Mefford et al., 2012]. All known cases until now have been reported as de novo occurring deletions when parents were available for testing. There have been no known offspring from individuals carrying the 15q24 microdeletion syndrome. Here we present a newborn girl and her twin brother, as well as their father, carrying a deletion on chromosome 15q24.
http://dx.doi.org/10.1016/j.ejmg.2014.12.006 1769-7212/Ó 2014 Elsevier Masson SAS. All rights reserved.
Please cite this article in press as: Samuelsson L, et al., Inherited 15q24 microdeletion syndrome in twins and their father with phenotypic variability, European Journal of Medical Genetics (2014), http://dx.doi.org/10.1016/j.ejmg.2014.12.006
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L. Samuelsson et al. / European Journal of Medical Genetics xxx (2014) 1e5
2. Patients and methods 2.1. Study subjects Twins, a girl and a boy, were born as the first children to non consanguineous Caucasian parents. The pregnancy was assisted by in vitro fertilization due to oligoasthenospermia in the father. During the pregnancy the mother had urinary tract infections but was otherwise healthy. Growth retardation was noted in twin number one and for this reason a cesarean section was done in week 38. The father’s medical history was reviewed after the twins were born. In his first years of life he had been thoroughly evaluated due to hypotonicity, delayed verbal and motor development, feeding difficulties and recurrent otitis and pneumonias. He received gammaglobulin treatment due to a decreased amount of IgG2. A submucous cleft palate was diagnosed as well as a sleep apnea syndrome. Both his hands had been operated due to proximally implanted thumbs. He had attended a school for children with mild intellectual disabilities and he now has unqualified work. The results of any cognitive assessments are not accessible but, according to his parents, he had a mild developmental delay. He had been evaluated for 22q11 syndrome, and a neuroepithelial cyst was found in the thalamus. Upon physical examination at 27 years of age, he exhibited mild dysmorphic facial features such as epicanthal folds, small mouth and long smooth philtrum. The index patient was the girl who had an asymmetrical growth retardation, birth weight 4 SD, birth length 0.5 SD and a head circumference 1 SD. Shortly after birth she developed respiratory symptoms and was for a short period of time in need of CPAP (Continuous Positive Airway Pressure) treatment. She was hypotonic and in need of tube feeding. Dysmorphic features were noted: down-slanted palpebral fissures, epicanthal folds, sparse eyebrows, posterior rotated ears, wide depressed nasal bridge, small mouth, thin upper lip, long smooth philtrum, micrognatia, cleft palate, single transverse palmar crease and a large clitoris. A discrete pulmonary stenosis was found. Her hips were treated with immobilization due to subluxation. Her respiratory difficulties became gradually more significant and were initially treated by positioning her on the side or stomach. Nevertheless her respiratory problems further increased with both central and obstructive apneas and desaturations. A pharyngeal nose tube was used to relieve her problems. After four months she was able to manage her airways without the aid of the tube. She also received a gastrostomy since her feeding difficulties continued. She also had problems with vomiting and constipation. Ophthalmological examination was normal and the hearing evaluation inconclusive. At the age of 9.5 months she was hypotonic, had joint laxicity and a minor developmental delay. She was able to sit unsupported for several minutes and used both hands. She made vocal sounds and had started do discriminate strangers. She was still in need of partly gastrostomy feeding. Her growth had improved, with weight at 2 SD, length at 1 SD and head circumference at 0.5 SD. Habilitation efforts were initiated. Her twin brother also had an asymmetrical growth retardation, weight 3.5 SD, length 0.5 SD and head circumference 1.5 SD at birth. In his first week of life a subluxation of the hips was diagnosed but no other obvious clinical abnormalities were seen at that time. From the age of one month his skin became dry and he developed a severe infection in the eczema. Further investigations discovered a multiple food allergy. Dysmorphic features were described: prominent forehead, down slanting palpebral fissures, hypertelorism, sparse eyebrows, wide, depressed nasal bridge, posterior rotated ears and retrognathia. At the age of 2.5 months he was hypotonic and was unable to turn his head when laid in a prone
position. He was fully bottle fed and had no respiratory problems. He had abducens nerve palsy in one eye. He had a normal echocardiography. His hearing evaluation was not conclusive and repeated examinations are planned. He had a normal genital appearance except a slightly curved penis. At the age of 9.5 months his psychomotor development was delayed, he was hypotonic and had a general joint laxicity. He had not developed complete head control, he could roll over, transfer objects between hands, and he babbled and was interested in social contact. His growth had improved, weighing 2 SD, length þ0.5 SD and head circumference 0 SD. He received treatment for eczema and ate special food due to the allergy. Habilitation efforts were also initiated for him. Clinical features of the twins and their father are shown in Table 1. 2.2. Genotype analysis Genomic DNA was isolated from peripheral blood samples using EZ1 DNA Blood 350 ml Kit from Qiagen. Samples were analyzed by high-density SNP array using the Genome-Wide Human SNP 6.0 Array, and CytoScan HD from Affymetrix. Data analyses were performed using the GTC software and Chromosome Analysis Suite (ChAS) from Affymetrix. Multiplex Ligation-dependent Probe Amplification (MLPA) was performed using kit P371 from MRCHolland. 3. Results The index patient was referred for molecular karyotyping in the neonatal period. This was included in her medical evaluation due to hypotonicity in conjunction with respiratory difficulties and dysmorphic features. Using a high-density SNP array, a deletion on chromosome 15q24 was detected in the patient. All other reported copy number variations were either recognized as polymorphisms or regarded as likely benign variations. The deleted region extends between base pairs 74,786,531 to 76,305,473 (GRCh37/hg19) and the size is approximately 1.52 Mb. Previous publications have described the genomic architecture of the chromosome 15q24 region and defined five blocks of segmental duplications (SD) where breakpoints commonly occur due to non-allelic homologous recombination (NAHR), [Andrieux et al., 2009; El-Hattab et al., 2009; Mefford et al., 2012] (Fig. 1). These SD blocks are commonly referred to as blocks A, B, C, D and E. In our patient the breakpoints are not within any SD block but between SD blocks BeC and DeE, see Fig. 1. Only approximately 0.71 Mb of the deleted region is located within the proposed 1.2 Mb SRO between block B and block C [Andrieux et al., 2009; IS et al., 2011; Magoulas and El-Hattab, 2012; McInnes et al., 2010; Mefford et al., 2012]. We used Multiplex Ligation-dependent Probe Amplification, MLPA, to confirm the finding and to investigate whether the patient’s twin brother and parents carry the same deletion. Probes in genes CLK3, CYP1A1 and CSK showed reduced dosage in agreement with a deletion for the patient, the twin brother and their father (data not shown). Analysis by high-resolution SNP array (CytoScan HD from Affymetrix) in the twin brother and father showed that deletion breakpoints are similar in the three cases, with no differences in genetic content (data not shown). 4. Discussion The 15q24 microdeletion syndrome is a rare and relative newly [Sharp et al., 2007] described syndrome with distinct clinical features. A diverse range of findings is described: mild to severe
Please cite this article in press as: Samuelsson L, et al., Inherited 15q24 microdeletion syndrome in twins and their father with phenotypic variability, European Journal of Medical Genetics (2014), http://dx.doi.org/10.1016/j.ejmg.2014.12.006
L. Samuelsson et al. / European Journal of Medical Genetics xxx (2014) 1e5
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Table 1 Clinical features of the twins and their father in comparison with previously reported features [Andrieux et al., 2009; El-Hattab et al., 2009, 2010; IS et al., 2011; Klopocki et al., 2008; Marshall et al., 2008; Masurel-Paulet et al., 2009; McInnes et al., 2010; Mefford et al., 2012; Sharp et al., 2007; Van Esch et al., 2009]. Features
Previously reported
Father
Girl
Boy
Developmental delay/Intellectual disability Speech delay Hypotonia/motor delay Joint laxity/hip instability Microcephalic Brain MRIs abnormalities Psychiatric symptoms Seizures Growth abnormalities Feeding difficulties/Failure to thrive Immunological disease
Yes. Global developmental delay; mild to severe
þ
þþ
þþ
Yes. Yes Yes Yes Yes Yes. Yes Yes. Yes Yes.
? þþ þþ 0 N.A. N.A. 0 þþ þþþ 0
Recurrent infections
Yes.
Respiratory difficulties
þþ Otitis þþþ
? þþþ þ 0 N.A. N.A. 0 þþ 0 þþ Eczema, allergy, asthma þ Otitis 0
þþ
þþ
Cleft palate
Yes: Pierre Robin sequence [Brun et al., 2012] diaphragmatic hernia [Van Esch et al., 2009] Yes. High anterior hairline, deep-set eyes, triangular shaped face. Yes. [Brun et al., 2012].
þ þþ N. A. 0 þ N.A. 0 N. A. þ þþ Decreased amount of IgG2, asthma þþ Otitis and pneumonia þþ Sleep apnea syndrome þ
þþ
0
Ear and hearing abnormalities
Yes. Conductive and sensorineural hearing loss.
? Inconclusive
? Inconclusive
Ocular abnormalities
Yes. Strabismus
þ Submucous þ Bilateral conductive sensorineural hearing loss N. A.
0
Limb abnormalities
Yes. Congenital malformations of the hands and feet.
þþ Proximal implanted thumbs
þ Abducens nerve palsy 0
Cardiac malformation Genital abnormalities Gastrointestinal abnormalities
Yes Yes. Hypospadias, micropenis, labial adhesions Yes. Inguinal hernia, intestinal atresia
Hematology abnormalities
Yes. Myeloproliferative disease
N. A. þ þ Inguinal hernia 0
Dysmorphic facial features
Marked delayed or absent
ADHD, autism, psychiatric disorders IUGR, GH deficiency Dry skin
(þ) Single transverse palmar crease þ 0 0 0
0 (þ) 0 0
N.A. ¼ data not available, (þ) ¼ uncertain clinical significance, þ ¼ mild clinical significance, þþ ¼ moderate clinical significance, þþþ ¼ severe clinical significance, ? ¼ inconclusive.
developmental delay, growth retardation, dysmorphic features, different malformations and abnormalities (Table 1) [Andrieux et al., 2009; El-Hattab et al., 2009, 2010; IS et al., 2011; Klopocki et al., 2008; Marshall et al., 2008; Masurel-Paulet et al., 2009; McInnes et al., 2010; Mefford et al., 2012; Sharp et al., 2007; Van Esch et al., 2009].
The majority of previously reported patients have large deletions with breakpoints in one or more of five blocks of segmental duplications. Based on the localization of the breakpoints, a shortest region of overlap (SRO) has been proposed between SD blocks B and C since this region is deleted in more than 70 per cent of all patients [Mefford et al., 2012]. However, deletions with
Fig. 1. Schematic representation of the structure of the 15q24 region. The black bars represent localization of the four most commonly deleted regions, extending between breakpoints AeD, BeE, AeC and BeD, respectively. The light gray box shows the shared critical region. The white bar represents the 1.52 Mb deletion in our index patient, with the gene content of the deleted region shown below (from UCSC GRCh37/hg19).
Please cite this article in press as: Samuelsson L, et al., Inherited 15q24 microdeletion syndrome in twins and their father with phenotypic variability, European Journal of Medical Genetics (2014), http://dx.doi.org/10.1016/j.ejmg.2014.12.006
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L. Samuelsson et al. / European Journal of Medical Genetics xxx (2014) 1e5
atypical breakpoints have been described [Andrieux et al., 2009; ElHattab et al., 2009; McInnes et al., 2010; Mefford et al., 2012; Narumi et al., 2012]. Amongst these, there are several cases where only part of the proposed SRO is deleted [Brun et al., 2012; McInnes et al., 2010; Mefford et al., 2012; Narumi et al., 2012]. A number of candidate genes have been proposed [Andrieux et al., 2009; El-Hattab et al., 2010; McInnes et al., 2010] and, of these, ARID3B (AT rich interactive domain 3B), CSK (cytoplasmic-src tyrosine kinase), CPLX3 (complexin 3) and SIN3A (transcriptional co-repressor Sin3A) are deleted in our patient but not in all patients with atypical deletions including parts of the proposed SRO. In fact, our patient and patient 1 in a study by Mefford and colleagues [Mefford et al., 2012] both have breakpoints between block B and C but they are non-overlapping, separated by 143 kbp. These patients do not share any deleted genetic information. If haploinsufficiency of one or more gene/s is the underlying cause of the 15q24 microdeletion syndrome, different sets of genes might give rise to the phenotypic spectrum of this syndrome. Alternatively, the deletion of regulatory sequences within and outside the SRO might explain the existence of non-overlapping deletions leading to a similar phenotype. To the best of our knowledge, our report represents the first inherited cases and also the first sibling cases of the 15q24 syndrome. A clear difference in the phenotype between the affected family members is shown although they all shared the same deletion. The twin girl was more severely affected in the neonatal period. She was referred for molecular karyotyping due to her being hypotonic and somewhat dysmorphic. Upon further investigations undertaken in the family, it was shown that the brother also carried the deletion. His symptomatology became gradually more obvious. Possible explanations at this point included germinal mosaicism (not previously described with this microdeletion syndrome) or inheritance from one of the parents. The familial investigation pointed to the twins’ father also being a carrier. A more detailed family history revealed that the father had symptoms consistent with the 15q24 microdeletion syndrome such as low muscle tonus, feeding difficulties, bilateral conductive sensorineural hearing loss and mild intellectual deficiency/developmental delay (Table 1). He was previously undiagnosed. Urogenital malformations have been described as a part of this syndrome [El-Hattab et al., 2010; Mefford et al., 2012]. Our adult male patient exhibits no such malformations but had documented reduced fertility, making assisted conception necessary. This fact could indicate that other factors such as haploinsufficiency of one or more genes located on the 15q24 chromosomal region are responsible for the infertility, e.g. leading to decreased sperm production. Alternatively, mitotic or meiotic disjunction and the production of sperms with unviable chromosomal aberrations as a result could be responsible for the oligoasthenospermia. Since only a few adult patients with 15q24 syndrome are described today and this is the first case of parental transmission, the degree of infertility in the syndrome has to be evaluated further. The father had a submucous cleft palate and the girl a cleft palate. To our knowledge, only one patient with the 15q24 microdeletion syndrome has earlier been identified as having a cleft palate [Brun et al., 2012]. This patient has a similar deletion with respect to both size and location. Among the deleted genes in this region, there are no obvious candidates that could lead to cleft palate. It is however not inconceivable that one or more of these genes could be involved in a pathway critical for the development of the oral region. As more cases of the syndrome are described it should emerge whether cleft palate is part of the phenotypic spectrum.
The current relatively mild developmental and language features in the father are not unique, although most reports describe markedly absent or delayed speech development and mild to moderate intellectual disability [Brun et al., 2012]. This might partly be explained by the majority of cases presented earlier having been in children [El-Hattab et al., 2010; Mefford et al., 2012] and little is known about long term variation in developmental outcome. The couple was referred to a specialist clinic for reproductive problems. Chromosomal studies in the father revealed a normal karyotype. If his mild intellectual deficiency and congenital anomalies had been taken into account, an array analysis could have been considered instead [Miller et al., 2010; Tucker et al., 2014]. This would have revealed the 15q24 deletion and made prenatal diagnosis and/or preimplantation genetic diagnosis possible. 5. Conclusions The majority of cases of 15q24 microdeletion syndrome have been diagnosed in children. As these children mature into adults, more cases of parental transmission can occur, especially if no urogenital malformations are present. Array analysis could be considered as a first-tier analysis in cases of infertility and intellectual deficiency/developmental delay in undiagnosed adults in analogy to the existing consensus regarding cases of intellectual deficiency/developmental delay and congenital anomalies [Miller et al., 2010]. Acknowledgment We are grateful to the family who provided the clinical information and gave permission to publish it. We would also like to acknowledge Dr Jan Pedersen, who partly initiated this work. References Andrieux J, Dubourg C, Rio M, Attie-Bitach T, Delaby E, Mathieu M, et al. Genotypephenotype correlation in four 15q24 deleted patients identified by array-CGH. Am J Med Genet A 2009;149A:2813e9. Brun A, Cailley D, Toutain J, Bouron J, Arveiler B, Lacombe D, et al. 1.5 Mb microdeletion in 15q24 in a patient with mild OAVS phenotype. Eur J Med Genet 2012;55:135e9. El-Hattab AW, Smolarek TA, Walker ME, Schorry EK, Immken LL, Patel G, et al. Redefined genomic architecture in 15q24 directed by patient deletion/duplication breakpoint mapping. Hum Genet 2009;126:589e602. El-Hattab AW, Zhang F, Maxim R, Christensen KM, Ward JC, Hines-Dowell S, et al. Deletion and duplication of 15q24: molecular mechanisms and potential modification by additional copy number variants. Genet Med 2010;12:573e86. IS LN, Chin WH, EC PL, Tan EC. An additional case of the recurrent 15q24.1 microdeletion syndrome and review of the literature. Twin Res Hum Genet 2011;14: 333e9. Klopocki E, Graul-Neumann LM, Grieben U, Tonnies H, Ropers HH, Horn D, et al. A further case of the recurrent 15q24 microdeletion syndrome, detected by array CGH. Eur J Pediatr 2008;167:903e8. Magoulas PL, El-Hattab AW. Chromosome 15q24 microdeletion syndrome. Orphanet J Rare Dis 2012;7:2. Marshall CR, Noor A, Vincent JB, Lionel AC, Feuk L, Skaug J, et al. Structural variation of chromosomes in autism spectrum disorder. Am J Hum Genet 2008;82:477e88. Masurel-Paulet A, Callier P, Thauvin-Robinet C, Chouchane M, Mejean N, Marle N, et al. Multiple cysts of the corpus callosum and psychomotor delay in a patient with a 3.1 Mb 15q24.1q24.2 interstitial deletion identified by array-CGH. Am J Med Genet A 2009;149A:1504e10. McInnes LA, Nakamine A, Pilorge M, Brandt T, Jimenez Gonzalez P, Fallas M, et al. A large-scale survey of the novel 15q24 microdeletion syndrome in autism spectrum disorders identifies an atypical deletion that narrows the critical region. Mol Autism 2010;1:5. Mefford HC, Rosenfeld JA, Shur N, Slavotinek AM, Cox VA, Hennekam RC, et al. Further clinical and molecular delineation of the 15q24 microdeletion syndrome. J Med Genet 2012;49:110e8. Miller DT, Adam MP, Aradhya S, Biesecker LG, Brothman AR, Carter NP, et al. Consensus statement: chromosomal microarray is a first-tier clinical diagnostic test for individuals with developmental disabilities or congenital anomalies. Am J Hum Genet 2010;86:749e64.
Please cite this article in press as: Samuelsson L, et al., Inherited 15q24 microdeletion syndrome in twins and their father with phenotypic variability, European Journal of Medical Genetics (2014), http://dx.doi.org/10.1016/j.ejmg.2014.12.006
L. Samuelsson et al. / European Journal of Medical Genetics xxx (2014) 1e5 Narumi Y, Shiohara M, Wakui K, Hama A, Kojima S, Yoshikawa K, et al. Myelodysplastic syndrome in a child with 15q24 deletion syndrome. Am J Med Genet A 2012;158A:412e6. Sharp AJ, Selzer RR, Veltman JA, Gimelli S, Gimelli G, Striano P, et al. Characterization of a recurrent 15q24 microdeletion syndrome. Hum Mol Genet 2007;16: 567e72.
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Tucker T, Zahir FR, Griffith M, Delaney A, Chai D, Tsang E, et al. Single exonresolution targeted chromosomal microarray analysis of known and candidate intellectual disability genes. Eur J Hum Genet 2014;22:792e800. Van Esch H, Backx L, Pijkels E, Fryns JP. Congenital diaphragmatic hernia is part of the new 15q24 microdeletion syndrome. Eur J Med Genet 2009;52:153e6.
Please cite this article in press as: Samuelsson L, et al., Inherited 15q24 microdeletion syndrome in twins and their father with phenotypic variability, European Journal of Medical Genetics (2014), http://dx.doi.org/10.1016/j.ejmg.2014.12.006
Contents lists available at ScienceDirect
European Journal of Medical Genetics journal homepage: http://www.elsevier.com/locate/ejmg
Clinical report
Inherited 15q24 microdeletion syndrome in twins and their father with phenotypic variability Lena Samuelsson a, Theofanis Zagoras a, Maria Hafström b, c, d, * a
Department of Clinical Genetics, Sahlgrenska University Hospital, Sweden Department of Pediatrics, Institute of Clinical Sciences, The Queen Silvia Children’s Hospital, University of Gothenburg, Göteborg, Sweden c Department of Paediatrics, St. Olavs Hospital, Norway d Department of Laboratory Medicine, Children’s and Women’s Health, Norwegian University of Science and Technology, Trondheim, Norway b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 1 June 2014 Accepted 1 December 2014 Available online xxx
Background: Deletions including chromosome 15q24 have been delineated in recent years as a separate syndrome with phenotypic variability. Here we report a familial 15q24 deletion and further contribute to the phenotypic description of this syndrome. Methods: Molecular karyotyping and description of the phenotype of three patients in the same family with a 15q24 deletion. Results: Parental transmission of the 15q24 deletion syndrome is described in the same family. The affected, the father and his twin offspring, all exhibit the typical facial features, signs and symptoms consistent with the syndromic phenotype. A distinct phenotypic variability is nevertheless noted although they all share the same deletion. Conclusions: These three patients are to our knowledge the first described cases of 15q24 syndrome in the same family. Urogenital malformations have previously been described as a part of this syndrome. Our adult male patient exhibits no such malformations but has a documented reduced fertility. This fact points to other factors such as haploinsufficiency of one and/or further genes on 15q24 as being responsible for the infertility. Array analysis could be considered as a first hand analysis in the investigation of cases of infertility and intellectual deficiency in adults in analogy to the existing consensus regarding cases of intellectual deficiency in children. Ó 2014 Elsevier Masson SAS. All rights reserved.
Keywords: Chromosome deletion Intellectual disability Chromosome disorders Chromosomes human pair 15 Microarray analysis
1. Introduction The establishment of array-based molecular karyotyping has in recent years led to the discovery and precise delineation of copy number variants and microdeletion/duplication syndromes that have previously been unknown. Deletions including 15q24 were first described a few years ago [Sharp et al., 2007]. To date, more than 30 such cases have been reported in the literature [Andrieux et al., 2009; El-Hattab et al., 2009, 2010; IS et al., 2011; Klopocki et al., 2008; Marshall et al., 2008; Masurel-Paulet et al., 2009; McInnes et al., 2010; Mefford et al., 2012; Sharp et al., 2007; Van Esch et al., 2009]. The syndrome is associated with intellectual disability, characteristic
* Corresponding author. Department of Pediatrics, Institute of Clinical Sciences, The Queen Silvia Children’s Hospital, University of Gothenburg, S-416 85 Göteborg, Sweden. Tel.: þ46 702 806269; fax: þ46 31 3434316. E-mail address: [email protected] (M. Hafström).
facial features such as long face, hypertelorism and epicanthal folds as well as growth retardation, genital anomalies and skeletal deformities. Most of the 15q24 deletions’ breakpoints are located in one of five blocks of segmental duplications (SD), commonly referred to as SD block 15q24 A, B, C, D and E [ElHattab et al., 2009]. A smallest region of overlap (SRO) has been delineated and encompasses an approximately 1.2 Mb region between 15q24B and 15q24C since the majority of patients have deletions including this region [Andrieux et al., 2009; IS et al., 2011; Magoulas and El-Hattab, 2012; McInnes et al., 2010; Mefford et al., 2012]. In addition, at least two patients have been reported that have a deletion completely outside the region between block B and block C [Mefford et al., 2012]. All known cases until now have been reported as de novo occurring deletions when parents were available for testing. There have been no known offspring from individuals carrying the 15q24 microdeletion syndrome. Here we present a newborn girl and her twin brother, as well as their father, carrying a deletion on chromosome 15q24.
http://dx.doi.org/10.1016/j.ejmg.2014.12.006 1769-7212/Ó 2014 Elsevier Masson SAS. All rights reserved.
Please cite this article in press as: Samuelsson L, et al., Inherited 15q24 microdeletion syndrome in twins and their father with phenotypic variability, European Journal of Medical Genetics (2014), http://dx.doi.org/10.1016/j.ejmg.2014.12.006
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L. Samuelsson et al. / European Journal of Medical Genetics xxx (2014) 1e5
2. Patients and methods 2.1. Study subjects Twins, a girl and a boy, were born as the first children to non consanguineous Caucasian parents. The pregnancy was assisted by in vitro fertilization due to oligoasthenospermia in the father. During the pregnancy the mother had urinary tract infections but was otherwise healthy. Growth retardation was noted in twin number one and for this reason a cesarean section was done in week 38. The father’s medical history was reviewed after the twins were born. In his first years of life he had been thoroughly evaluated due to hypotonicity, delayed verbal and motor development, feeding difficulties and recurrent otitis and pneumonias. He received gammaglobulin treatment due to a decreased amount of IgG2. A submucous cleft palate was diagnosed as well as a sleep apnea syndrome. Both his hands had been operated due to proximally implanted thumbs. He had attended a school for children with mild intellectual disabilities and he now has unqualified work. The results of any cognitive assessments are not accessible but, according to his parents, he had a mild developmental delay. He had been evaluated for 22q11 syndrome, and a neuroepithelial cyst was found in the thalamus. Upon physical examination at 27 years of age, he exhibited mild dysmorphic facial features such as epicanthal folds, small mouth and long smooth philtrum. The index patient was the girl who had an asymmetrical growth retardation, birth weight 4 SD, birth length 0.5 SD and a head circumference 1 SD. Shortly after birth she developed respiratory symptoms and was for a short period of time in need of CPAP (Continuous Positive Airway Pressure) treatment. She was hypotonic and in need of tube feeding. Dysmorphic features were noted: down-slanted palpebral fissures, epicanthal folds, sparse eyebrows, posterior rotated ears, wide depressed nasal bridge, small mouth, thin upper lip, long smooth philtrum, micrognatia, cleft palate, single transverse palmar crease and a large clitoris. A discrete pulmonary stenosis was found. Her hips were treated with immobilization due to subluxation. Her respiratory difficulties became gradually more significant and were initially treated by positioning her on the side or stomach. Nevertheless her respiratory problems further increased with both central and obstructive apneas and desaturations. A pharyngeal nose tube was used to relieve her problems. After four months she was able to manage her airways without the aid of the tube. She also received a gastrostomy since her feeding difficulties continued. She also had problems with vomiting and constipation. Ophthalmological examination was normal and the hearing evaluation inconclusive. At the age of 9.5 months she was hypotonic, had joint laxicity and a minor developmental delay. She was able to sit unsupported for several minutes and used both hands. She made vocal sounds and had started do discriminate strangers. She was still in need of partly gastrostomy feeding. Her growth had improved, with weight at 2 SD, length at 1 SD and head circumference at 0.5 SD. Habilitation efforts were initiated. Her twin brother also had an asymmetrical growth retardation, weight 3.5 SD, length 0.5 SD and head circumference 1.5 SD at birth. In his first week of life a subluxation of the hips was diagnosed but no other obvious clinical abnormalities were seen at that time. From the age of one month his skin became dry and he developed a severe infection in the eczema. Further investigations discovered a multiple food allergy. Dysmorphic features were described: prominent forehead, down slanting palpebral fissures, hypertelorism, sparse eyebrows, wide, depressed nasal bridge, posterior rotated ears and retrognathia. At the age of 2.5 months he was hypotonic and was unable to turn his head when laid in a prone
position. He was fully bottle fed and had no respiratory problems. He had abducens nerve palsy in one eye. He had a normal echocardiography. His hearing evaluation was not conclusive and repeated examinations are planned. He had a normal genital appearance except a slightly curved penis. At the age of 9.5 months his psychomotor development was delayed, he was hypotonic and had a general joint laxicity. He had not developed complete head control, he could roll over, transfer objects between hands, and he babbled and was interested in social contact. His growth had improved, weighing 2 SD, length þ0.5 SD and head circumference 0 SD. He received treatment for eczema and ate special food due to the allergy. Habilitation efforts were also initiated for him. Clinical features of the twins and their father are shown in Table 1. 2.2. Genotype analysis Genomic DNA was isolated from peripheral blood samples using EZ1 DNA Blood 350 ml Kit from Qiagen. Samples were analyzed by high-density SNP array using the Genome-Wide Human SNP 6.0 Array, and CytoScan HD from Affymetrix. Data analyses were performed using the GTC software and Chromosome Analysis Suite (ChAS) from Affymetrix. Multiplex Ligation-dependent Probe Amplification (MLPA) was performed using kit P371 from MRCHolland. 3. Results The index patient was referred for molecular karyotyping in the neonatal period. This was included in her medical evaluation due to hypotonicity in conjunction with respiratory difficulties and dysmorphic features. Using a high-density SNP array, a deletion on chromosome 15q24 was detected in the patient. All other reported copy number variations were either recognized as polymorphisms or regarded as likely benign variations. The deleted region extends between base pairs 74,786,531 to 76,305,473 (GRCh37/hg19) and the size is approximately 1.52 Mb. Previous publications have described the genomic architecture of the chromosome 15q24 region and defined five blocks of segmental duplications (SD) where breakpoints commonly occur due to non-allelic homologous recombination (NAHR), [Andrieux et al., 2009; El-Hattab et al., 2009; Mefford et al., 2012] (Fig. 1). These SD blocks are commonly referred to as blocks A, B, C, D and E. In our patient the breakpoints are not within any SD block but between SD blocks BeC and DeE, see Fig. 1. Only approximately 0.71 Mb of the deleted region is located within the proposed 1.2 Mb SRO between block B and block C [Andrieux et al., 2009; IS et al., 2011; Magoulas and El-Hattab, 2012; McInnes et al., 2010; Mefford et al., 2012]. We used Multiplex Ligation-dependent Probe Amplification, MLPA, to confirm the finding and to investigate whether the patient’s twin brother and parents carry the same deletion. Probes in genes CLK3, CYP1A1 and CSK showed reduced dosage in agreement with a deletion for the patient, the twin brother and their father (data not shown). Analysis by high-resolution SNP array (CytoScan HD from Affymetrix) in the twin brother and father showed that deletion breakpoints are similar in the three cases, with no differences in genetic content (data not shown). 4. Discussion The 15q24 microdeletion syndrome is a rare and relative newly [Sharp et al., 2007] described syndrome with distinct clinical features. A diverse range of findings is described: mild to severe
Please cite this article in press as: Samuelsson L, et al., Inherited 15q24 microdeletion syndrome in twins and their father with phenotypic variability, European Journal of Medical Genetics (2014), http://dx.doi.org/10.1016/j.ejmg.2014.12.006
L. Samuelsson et al. / European Journal of Medical Genetics xxx (2014) 1e5
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Table 1 Clinical features of the twins and their father in comparison with previously reported features [Andrieux et al., 2009; El-Hattab et al., 2009, 2010; IS et al., 2011; Klopocki et al., 2008; Marshall et al., 2008; Masurel-Paulet et al., 2009; McInnes et al., 2010; Mefford et al., 2012; Sharp et al., 2007; Van Esch et al., 2009]. Features
Previously reported
Father
Girl
Boy
Developmental delay/Intellectual disability Speech delay Hypotonia/motor delay Joint laxity/hip instability Microcephalic Brain MRIs abnormalities Psychiatric symptoms Seizures Growth abnormalities Feeding difficulties/Failure to thrive Immunological disease
Yes. Global developmental delay; mild to severe
þ
þþ
þþ
Yes. Yes Yes Yes Yes Yes. Yes Yes. Yes Yes.
? þþ þþ 0 N.A. N.A. 0 þþ þþþ 0
Recurrent infections
Yes.
Respiratory difficulties
þþ Otitis þþþ
? þþþ þ 0 N.A. N.A. 0 þþ 0 þþ Eczema, allergy, asthma þ Otitis 0
þþ
þþ
Cleft palate
Yes: Pierre Robin sequence [Brun et al., 2012] diaphragmatic hernia [Van Esch et al., 2009] Yes. High anterior hairline, deep-set eyes, triangular shaped face. Yes. [Brun et al., 2012].
þ þþ N. A. 0 þ N.A. 0 N. A. þ þþ Decreased amount of IgG2, asthma þþ Otitis and pneumonia þþ Sleep apnea syndrome þ
þþ
0
Ear and hearing abnormalities
Yes. Conductive and sensorineural hearing loss.
? Inconclusive
? Inconclusive
Ocular abnormalities
Yes. Strabismus
þ Submucous þ Bilateral conductive sensorineural hearing loss N. A.
0
Limb abnormalities
Yes. Congenital malformations of the hands and feet.
þþ Proximal implanted thumbs
þ Abducens nerve palsy 0
Cardiac malformation Genital abnormalities Gastrointestinal abnormalities
Yes Yes. Hypospadias, micropenis, labial adhesions Yes. Inguinal hernia, intestinal atresia
Hematology abnormalities
Yes. Myeloproliferative disease
N. A. þ þ Inguinal hernia 0
Dysmorphic facial features
Marked delayed or absent
ADHD, autism, psychiatric disorders IUGR, GH deficiency Dry skin
(þ) Single transverse palmar crease þ 0 0 0
0 (þ) 0 0
N.A. ¼ data not available, (þ) ¼ uncertain clinical significance, þ ¼ mild clinical significance, þþ ¼ moderate clinical significance, þþþ ¼ severe clinical significance, ? ¼ inconclusive.
developmental delay, growth retardation, dysmorphic features, different malformations and abnormalities (Table 1) [Andrieux et al., 2009; El-Hattab et al., 2009, 2010; IS et al., 2011; Klopocki et al., 2008; Marshall et al., 2008; Masurel-Paulet et al., 2009; McInnes et al., 2010; Mefford et al., 2012; Sharp et al., 2007; Van Esch et al., 2009].
The majority of previously reported patients have large deletions with breakpoints in one or more of five blocks of segmental duplications. Based on the localization of the breakpoints, a shortest region of overlap (SRO) has been proposed between SD blocks B and C since this region is deleted in more than 70 per cent of all patients [Mefford et al., 2012]. However, deletions with
Fig. 1. Schematic representation of the structure of the 15q24 region. The black bars represent localization of the four most commonly deleted regions, extending between breakpoints AeD, BeE, AeC and BeD, respectively. The light gray box shows the shared critical region. The white bar represents the 1.52 Mb deletion in our index patient, with the gene content of the deleted region shown below (from UCSC GRCh37/hg19).
Please cite this article in press as: Samuelsson L, et al., Inherited 15q24 microdeletion syndrome in twins and their father with phenotypic variability, European Journal of Medical Genetics (2014), http://dx.doi.org/10.1016/j.ejmg.2014.12.006
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L. Samuelsson et al. / European Journal of Medical Genetics xxx (2014) 1e5
atypical breakpoints have been described [Andrieux et al., 2009; ElHattab et al., 2009; McInnes et al., 2010; Mefford et al., 2012; Narumi et al., 2012]. Amongst these, there are several cases where only part of the proposed SRO is deleted [Brun et al., 2012; McInnes et al., 2010; Mefford et al., 2012; Narumi et al., 2012]. A number of candidate genes have been proposed [Andrieux et al., 2009; El-Hattab et al., 2010; McInnes et al., 2010] and, of these, ARID3B (AT rich interactive domain 3B), CSK (cytoplasmic-src tyrosine kinase), CPLX3 (complexin 3) and SIN3A (transcriptional co-repressor Sin3A) are deleted in our patient but not in all patients with atypical deletions including parts of the proposed SRO. In fact, our patient and patient 1 in a study by Mefford and colleagues [Mefford et al., 2012] both have breakpoints between block B and C but they are non-overlapping, separated by 143 kbp. These patients do not share any deleted genetic information. If haploinsufficiency of one or more gene/s is the underlying cause of the 15q24 microdeletion syndrome, different sets of genes might give rise to the phenotypic spectrum of this syndrome. Alternatively, the deletion of regulatory sequences within and outside the SRO might explain the existence of non-overlapping deletions leading to a similar phenotype. To the best of our knowledge, our report represents the first inherited cases and also the first sibling cases of the 15q24 syndrome. A clear difference in the phenotype between the affected family members is shown although they all shared the same deletion. The twin girl was more severely affected in the neonatal period. She was referred for molecular karyotyping due to her being hypotonic and somewhat dysmorphic. Upon further investigations undertaken in the family, it was shown that the brother also carried the deletion. His symptomatology became gradually more obvious. Possible explanations at this point included germinal mosaicism (not previously described with this microdeletion syndrome) or inheritance from one of the parents. The familial investigation pointed to the twins’ father also being a carrier. A more detailed family history revealed that the father had symptoms consistent with the 15q24 microdeletion syndrome such as low muscle tonus, feeding difficulties, bilateral conductive sensorineural hearing loss and mild intellectual deficiency/developmental delay (Table 1). He was previously undiagnosed. Urogenital malformations have been described as a part of this syndrome [El-Hattab et al., 2010; Mefford et al., 2012]. Our adult male patient exhibits no such malformations but had documented reduced fertility, making assisted conception necessary. This fact could indicate that other factors such as haploinsufficiency of one or more genes located on the 15q24 chromosomal region are responsible for the infertility, e.g. leading to decreased sperm production. Alternatively, mitotic or meiotic disjunction and the production of sperms with unviable chromosomal aberrations as a result could be responsible for the oligoasthenospermia. Since only a few adult patients with 15q24 syndrome are described today and this is the first case of parental transmission, the degree of infertility in the syndrome has to be evaluated further. The father had a submucous cleft palate and the girl a cleft palate. To our knowledge, only one patient with the 15q24 microdeletion syndrome has earlier been identified as having a cleft palate [Brun et al., 2012]. This patient has a similar deletion with respect to both size and location. Among the deleted genes in this region, there are no obvious candidates that could lead to cleft palate. It is however not inconceivable that one or more of these genes could be involved in a pathway critical for the development of the oral region. As more cases of the syndrome are described it should emerge whether cleft palate is part of the phenotypic spectrum.
The current relatively mild developmental and language features in the father are not unique, although most reports describe markedly absent or delayed speech development and mild to moderate intellectual disability [Brun et al., 2012]. This might partly be explained by the majority of cases presented earlier having been in children [El-Hattab et al., 2010; Mefford et al., 2012] and little is known about long term variation in developmental outcome. The couple was referred to a specialist clinic for reproductive problems. Chromosomal studies in the father revealed a normal karyotype. If his mild intellectual deficiency and congenital anomalies had been taken into account, an array analysis could have been considered instead [Miller et al., 2010; Tucker et al., 2014]. This would have revealed the 15q24 deletion and made prenatal diagnosis and/or preimplantation genetic diagnosis possible. 5. Conclusions The majority of cases of 15q24 microdeletion syndrome have been diagnosed in children. As these children mature into adults, more cases of parental transmission can occur, especially if no urogenital malformations are present. Array analysis could be considered as a first-tier analysis in cases of infertility and intellectual deficiency/developmental delay in undiagnosed adults in analogy to the existing consensus regarding cases of intellectual deficiency/developmental delay and congenital anomalies [Miller et al., 2010]. Acknowledgment We are grateful to the family who provided the clinical information and gave permission to publish it. We would also like to acknowledge Dr Jan Pedersen, who partly initiated this work. References Andrieux J, Dubourg C, Rio M, Attie-Bitach T, Delaby E, Mathieu M, et al. Genotypephenotype correlation in four 15q24 deleted patients identified by array-CGH. Am J Med Genet A 2009;149A:2813e9. Brun A, Cailley D, Toutain J, Bouron J, Arveiler B, Lacombe D, et al. 1.5 Mb microdeletion in 15q24 in a patient with mild OAVS phenotype. Eur J Med Genet 2012;55:135e9. El-Hattab AW, Smolarek TA, Walker ME, Schorry EK, Immken LL, Patel G, et al. Redefined genomic architecture in 15q24 directed by patient deletion/duplication breakpoint mapping. Hum Genet 2009;126:589e602. El-Hattab AW, Zhang F, Maxim R, Christensen KM, Ward JC, Hines-Dowell S, et al. Deletion and duplication of 15q24: molecular mechanisms and potential modification by additional copy number variants. Genet Med 2010;12:573e86. IS LN, Chin WH, EC PL, Tan EC. An additional case of the recurrent 15q24.1 microdeletion syndrome and review of the literature. Twin Res Hum Genet 2011;14: 333e9. Klopocki E, Graul-Neumann LM, Grieben U, Tonnies H, Ropers HH, Horn D, et al. A further case of the recurrent 15q24 microdeletion syndrome, detected by array CGH. Eur J Pediatr 2008;167:903e8. Magoulas PL, El-Hattab AW. Chromosome 15q24 microdeletion syndrome. Orphanet J Rare Dis 2012;7:2. Marshall CR, Noor A, Vincent JB, Lionel AC, Feuk L, Skaug J, et al. Structural variation of chromosomes in autism spectrum disorder. Am J Hum Genet 2008;82:477e88. Masurel-Paulet A, Callier P, Thauvin-Robinet C, Chouchane M, Mejean N, Marle N, et al. Multiple cysts of the corpus callosum and psychomotor delay in a patient with a 3.1 Mb 15q24.1q24.2 interstitial deletion identified by array-CGH. Am J Med Genet A 2009;149A:1504e10. McInnes LA, Nakamine A, Pilorge M, Brandt T, Jimenez Gonzalez P, Fallas M, et al. A large-scale survey of the novel 15q24 microdeletion syndrome in autism spectrum disorders identifies an atypical deletion that narrows the critical region. Mol Autism 2010;1:5. Mefford HC, Rosenfeld JA, Shur N, Slavotinek AM, Cox VA, Hennekam RC, et al. Further clinical and molecular delineation of the 15q24 microdeletion syndrome. J Med Genet 2012;49:110e8. Miller DT, Adam MP, Aradhya S, Biesecker LG, Brothman AR, Carter NP, et al. Consensus statement: chromosomal microarray is a first-tier clinical diagnostic test for individuals with developmental disabilities or congenital anomalies. Am J Hum Genet 2010;86:749e64.
Please cite this article in press as: Samuelsson L, et al., Inherited 15q24 microdeletion syndrome in twins and their father with phenotypic variability, European Journal of Medical Genetics (2014), http://dx.doi.org/10.1016/j.ejmg.2014.12.006
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Please cite this article in press as: Samuelsson L, et al., Inherited 15q24 microdeletion syndrome in twins and their father with phenotypic variability, European Journal of Medical Genetics (2014), http://dx.doi.org/10.1016/j.ejmg.2014.12.006