- Email: [email protected]
A serum response factor homologue is expressed in ectodermal tissues during development of the crustacean Artemia franciscana
Mechanisms of Development 96 (2000) 229±232
www.elsevier.com/locate/modo
Gene expression pattern
A serum response factor homologue is expressed in ectodermal tissues during development of the crustacean Artemia franciscana Marie-Carmen Casero, Leandro Sastre* Instituto de Investigaciones BiomeÂdicas CSIC/ UAM, Arturo Duperier, 4, 28029 Madrid, Spain Received 7 April 2000; received in revised form 31 May 2000; accepted 13 June 2000
Abstract Complementary DNA clones have been isolated from the crustacean Artemia franciscana coding for a serum response factor (SRF)homologue that is more than 96% identical to human and Drosophila melanogaster SRFs in their MADS boxes. The SRF homologue is expressed in ectodermal tissues, as determined by in situ hybridization experiments. A SRF-binding site has been identi®ed in the promoter region of the Actin403 gene that is also expressed in ectodermal tissues, in accordance with its transcriptional regulation by the SRF homologue. The mRNA coding for A. franciscana SRF is present at similar levels in cryptobiotic encysted embryos and in developing nauplii. However, there is a signi®cant increase in CArG-binding activity at the later developmental stage, indicating a postranscriptional regulation of SRF during A. franciscana embryonic development. q 2000 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Actin; Artemia franciscana; Brine shrimp; CArG-box; Crustacean; Development; Digestive tube; Ectoderm; Epidermis; Gene expression; Gene regulation; In situ hybridization; MADS-box; Serum response element; Serum response factor; Transcription factor; Transcription
In situ hybridization studies in chickens (Croissant et al., 1996) and mice (Belaguli et al., 1997; Arsenian et al., 1998) showed high levels of serum response factor (SRF) expression at early developmental stages in the heart and the myotomal region of the somites. At later stages SRF is strongly expressed in smooth, cardiac and skeletal muscle tissues (Croissant et al., 1996) which suggest an important role for SRF in muscle development. A Srf-homologue gene has been identi®ed in Drosophila melanogaster that is expressed at high levels in the terminal cells of the trachea at larval stages (Affolter et al., 1994) and in the intervein regions of the adult wing (Montagne et al., 1996). These data indicate that SRF plays a very different function in D. melanogaster than in vertebrates. The Srf-homologue gene from the slime mold Dictyostelium discoideurn is expressed at high levels in prespore and spore cells. Interruption of the gene affects spore terminal differentiation (Escalante and Sastre, 1998). Despite the diversity of functions described for SRF in these organisms, the proteins display a high similarity at their MADS boxes, which are the main functional regions of the proteins.
1. Results cDNA clones coding for the putative A. franciscana SRF homologue were obtained after screening 500 000 clones of a cDNA library made from adults RNA (Palmero et al., 1988) with a probe derived from D. melanogaster SRF (Affolter et al., 1994). The 2361 nt long cDNA (EMBL Accession number AJ251270) coded for a 317 amino acids polypeptide that showed a strong similarity to the
Fig. 1. Comparison of the amino acid sequence of A. fransciscana SRF homologue (Af) to those of H. sapiens (Hs) and D. melanogaster (Dm) SRFs around the human Serl03 phosphorilation site, indicated by the asterisk. Dots indicate amino acids identical to those of A. franciscana shown above. Slashes indicate gaps introduced to increase the similarities. Numbers at the beginning and the end of each sequence indicate the position of the ®rst and last amino acids shown in this alignment on the complete amino acid sequence of each protein.
* Corresponding author. Tel.: 134-91-585-4626; fax: 134-91-585-4587. E-mail address: [email protected] (L. Sastre). 0925-4773/00/$ - see front matter q 2000 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0925-477 3(00)00386-5
230
M.-C. Casero, L. Sastre / Mechanisms of Development 96 (2000) 229±232
Fig. 2. In situ hybridization analyses of SRF expression in A. franciscana nauplii. A. franciscana nauplii cultured for 40 h were cut in 10 mm sections and hybridized with digoxigenin-labeled RNA probes corresponding to the antisense SRF strand (SRF1, panels A±C) or the sense strand (SRF2, panels D±F) as described by Escalante et al. (1995). The upper panel shows a picture of an untreated, unsectioned nauplius of the same developmental stage to facilitate the identi®cation of the structures. Panels A and D show longitudinal sections of the nauplii where the head is located towards the right side and the dorsal region to the top. Panels (B±F) show transversal sections of the anterior region. Symbols: a, anterior; d, dorsal; e, epidermis; f, foregut; g, gut; h, hindgut. Bar represents 200 mm.
MADS-box sequences of SRF from D. melanogaster (98% identity) (Affolter et al., 1994), humans (96%) (Norman et al., 1988) and D. discoideum (85%) (Escalante and Sastre, 1998). The identity also extended to two regions contiguous to the MADS-box, a short N-terminal and a 50 amino acid long C-terminal regions. Another small region of amino acid sequence similarity, not previously described, was found between A. franciscana amino acids 55±63, D. melanogaster amino acids 107±116 and human amino acids 95± 104 (Fig. 1). This region contains human Ser103, that has been described to be phosphorilated, in vitro and in vivo, by the protein kinase MCKII (Heidenreich et al., 1999). The tissue-speci®c expression of SRF in A. franciscana nauplii was determined by in situ hybridization using digoxigenin-labeled RNA probes (Fig. 2A±C). Sense probes from the same cDNA region were used as negative controls (Fig. 2D±F). A strong hybridization, speci®c for the antisense probe, was obtained in all ectodermal tissues, including the epidermal tissue and the terminal regions of the digestive tube (foregut and hindgut). No SRF expression was observed in the muscles, located in the central part of the antennae and surrounding the digestive tube (Fig. 2A,B). The spatial pattern of expression observed for SRF mRNA in A. franciscana is very different from those described in vertebrates and D. melanogaster. The only common feature seems to be the conservation of the expression in some ectodermal tissues: neuroectodermal tissues in vertebrates (Herdegen et al., 1997; Croissant et al., 1996), terminal tracheal and wing intervein regions in D. melanogaster (Affolter et al., 1994; Montagne et al., 1996) and all ectodermal cells in A. franciscana. The A. franciscana Actin 403 gene promoter has been described to contain a canonical SRF-binding site (Ortega
Fig. 3. In situ hybridization analyses of Actin 403 expression in A. franciscana nauplii. A. franciscana nauplii cultured for 40 h were cut in 10 mm sections and hybridized with ¯uorescein-labeled oligonucleotides 44 (5 0 -GGTGGCATCTTCACTCTTGGACATAAGCAG-3 0 ), complementary to the 3 0 untranslated region of Actin403 mRNA (panel A), or 11 (5 0 -CGAGACTTACTAAATCTTAGAAGACTGGTG-3 0 ), complementary to the 3 0 untranslated region of Actin205 mRNA (panel B), or with a digoxigenin-labeled RNA probe complementary to the 3 0 untranslated region of Actin403 mRNA (lanes C and D). Panels (A,B) show transversal sections of the anterior region of the nauplii. Panels (C,D) show longitudinal sections of the anterior and posterior region of the nauplii, respectively. Symbols: a, anterior; d, dorsal; e, epidermis; f, foregut; g, gut; h, hindgut; l, labrum. Bar represents 200 mm.
M.-C. Casero, L. Sastre / Mechanisms of Development 96 (2000) 229±232
231
mia is the activation of the encysted embryos, that are in a cryptobiotic stage. The amount of SRF mRNA expressed during development of A. franciscana encysted embryos was determined by Northern blot (Fig. 4A). The SRF cDNA clone used as probe hybridized with two RNAs of 18 and 1.8 kb. The amount of both RNAs remained constant during the period of embryonic development studied, from the encysted embryos (0 h) to ®rst instar nauplii (23 h). SRF binding activity was determined at different developmental stages by gel retardation assays. The results are shown in Fig. 4B. Naupliar nuclear extracts originated a retardation band that was speci®c for the SRF binding site. Nuclear extracts from encysted embryos produced a much weaker retardation band. These results show a clear induction of SRF activity during embryonic development, indicating a postranscriptional control of the expression and/or activity of this protein during A. franciscana embryonic development. Acknowledgements We are indebted to Dr Markus Affolter for the donation of the D. melanogaster SRF cDNA clone, to Drs Rosario Perona and Ricardo Escalante for critical reading of the manuscript and helpful discussions. This work has been supported by Grant PB95-0096 and PB98-0517 from the DireccioÂn General de EnsenÄanza Superior e InvestigacioÂn CientI®ca. References Fig. 4. Levels of SRF mRNA expression and serum response element (SRE)-binding activity during A. franciscana early development. Panel A: total RNA was obtained from A. franciscana encysted embryos either before (0 h) or after 4, 16, 20 or 23 h of development (lanes 0, 4, 16, 20 and 23, respectively). Fifteen micrograms of each RNA were analyzed on a 1.5% agarose-2.2 M Formaldehyde gel, transferred to nylon ®lters and hybridized to 32P-labeled A. franciscana SRF cDNA. The migration of the ribosomal RNAs used as markers is indicated at the right of the picture. Panel B: nuclear extracts were obtained from A. franciscana cryptobiotic embryos either untreated (cysts) or cultured for 20 h (nauplii). Thirty micrograms of nuclear extracts were incubated with the 32P-labeled oligonucleotide SRE (5 0 -ACATGACCATATAAGGTATTGCAGCT-3 0 ), either alone (lanes-) or in the presence of a 100-fold excess of the unlabeled oligonucleotides SRE, the CArG-mutated SRE* 5 0 -ACATGAACATACAAGGTATTGCAGCT-3 0 ) or the unrelated oligonucleotide Act (5 0 -CCAACATCATCACATGCACC-3 0 ) (lanes SRE, SRE* and Act, respectively), as previously described (Perona et al., 1997). Arrowheads indicate the migration of the SRE-speci®c retardation complexes.
et al., 1996). In situ hybridization experiments were performed using probes complementary to the 3 0 untranslated region of Actin403 mRNA. This gene was found to be expressed in the epidermis and the terminal regions of the digestive tube (foregut and hindgut) with a pattern of expression similar to that of the SRF homologue, in agreement with its transcriptional regulation by SRF (Fig. 3). An interesting aspect of transcriptional regulation in Arte-
Affolter, M., Montagne, J., Walldorf, U., Groppe, J., Kloter, U., LaRosa, M., Gehring, W.J., 1994. The Drosophila SRF homolog is expressed in a subset of tracheal cells and maps within a genomic region required for tracheal development. Development 120, 743±753. Arsenian, S., Weinhold, B., Oelgeschlager, M., Ruther, U., Nordheim, A., 1998. Serum response factor is essential for mesoderm formation during mouse embryogenesis. EMBO J. 17, 6289±6299. Belaguli, N.S., Schildmeyer, L.A., Schwartz, R.J., 1997. Organization and myogenic restricted expression of the murine serum response factor gene. A role for autoregulation. J. Biol. Chem. 272, 18222±18231. Croissant, J.D., Kim, J.H., Eichele, G., Goering, L., Lough, J., Prywes, R., Schwartz, R.J., 1996. Avian serum response factor expression restricted primarily to muscle cell lineages is required for alpha-actin gene transcription. Dev. Biol. 177, 250±264. Escalante, R., Sastre, L., 1998. A serum response factor homolog is required for spore differentiation in Dictyostelium. Development 125, 3801±3808. Escalante, R., GarcõÂa-SaÂez, A., Sastre, L., 1995. In situ hybridization analyses of Na K-ATPase alpha-subunit expression during early larval development of Artemia franciscana. J. Histochem. Cytochem. 43, 391±399. Heidenreich, O., Neininger, A., Schratt, C., Zinck, R., Cahill, M.A., Engel, K., Kotlyarov, A., Kraft, R., Kostka, S., Gaestel, M., Nordheim, A., 1999. MAPKAP kinase 2 phosphorylates serum response factor in vitro and in vivo. J. Biol. Chem. 274, 14434±14443. Herdegen, T., Blume, A., Buschmann, T., Georgakopoulos, E., Winter, C., Schmid, W., Hsieh, T.F., Zimmermann, M., Gass, P., 1997. Expression of activating transcription factor-2, serum response factor and cAMP/ Ca response element binding protein in the adult rat brain following
232
M.-C. Casero, L. Sastre / Mechanisms of Development 96 (2000) 229±232
generalized seizures, nerve ®ber lesion and ultraviolet irradiation. Neuroscience 81, 199±212. Montagne, J., Groppe, J., Guillemin, K., Krasnow, M.A., Gehring, W.J., Affolter, M., 1996. The Drosophila serum response factor gene is required for the formation of intervein tissue of the wing and is allelic to blistered. Development 122, 2589±2597. Norman, C., Runswick, M., Pollock, R., Treisman, R., 1988. Isolation and properties of cDNA clones encoding SRF, a transcription factor that binds to the c-fos serum response element. Cell 55, 989±1003.
Ortega, M.A., DõÂaz-Guerra, M., Sastre, L., 1996. Actin gene structure in two Artemia species A. franciscana and A. parthenogenetica. J. Mol. Evol. 43, 224±235. Palmero, I., Renart, J., Sastre, L., 1988. Isolation of cDNA clones coding for mitochondrial 16S ribosomal RNA from the crustacean Artemia. Gene 68, 239±248. Perona, R., Montaner, S., Saniger, L., SaÂnchez-PeÂrez, I., Bravo, R., Lacal, J.C., 1997. Activation of the nuclear factor-kB by Rho CDC42, and Rac-1 proteins. Genes Dev. 11, 463±475.
www.elsevier.com/locate/modo
Gene expression pattern
A serum response factor homologue is expressed in ectodermal tissues during development of the crustacean Artemia franciscana Marie-Carmen Casero, Leandro Sastre* Instituto de Investigaciones BiomeÂdicas CSIC/ UAM, Arturo Duperier, 4, 28029 Madrid, Spain Received 7 April 2000; received in revised form 31 May 2000; accepted 13 June 2000
Abstract Complementary DNA clones have been isolated from the crustacean Artemia franciscana coding for a serum response factor (SRF)homologue that is more than 96% identical to human and Drosophila melanogaster SRFs in their MADS boxes. The SRF homologue is expressed in ectodermal tissues, as determined by in situ hybridization experiments. A SRF-binding site has been identi®ed in the promoter region of the Actin403 gene that is also expressed in ectodermal tissues, in accordance with its transcriptional regulation by the SRF homologue. The mRNA coding for A. franciscana SRF is present at similar levels in cryptobiotic encysted embryos and in developing nauplii. However, there is a signi®cant increase in CArG-binding activity at the later developmental stage, indicating a postranscriptional regulation of SRF during A. franciscana embryonic development. q 2000 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Actin; Artemia franciscana; Brine shrimp; CArG-box; Crustacean; Development; Digestive tube; Ectoderm; Epidermis; Gene expression; Gene regulation; In situ hybridization; MADS-box; Serum response element; Serum response factor; Transcription factor; Transcription
In situ hybridization studies in chickens (Croissant et al., 1996) and mice (Belaguli et al., 1997; Arsenian et al., 1998) showed high levels of serum response factor (SRF) expression at early developmental stages in the heart and the myotomal region of the somites. At later stages SRF is strongly expressed in smooth, cardiac and skeletal muscle tissues (Croissant et al., 1996) which suggest an important role for SRF in muscle development. A Srf-homologue gene has been identi®ed in Drosophila melanogaster that is expressed at high levels in the terminal cells of the trachea at larval stages (Affolter et al., 1994) and in the intervein regions of the adult wing (Montagne et al., 1996). These data indicate that SRF plays a very different function in D. melanogaster than in vertebrates. The Srf-homologue gene from the slime mold Dictyostelium discoideurn is expressed at high levels in prespore and spore cells. Interruption of the gene affects spore terminal differentiation (Escalante and Sastre, 1998). Despite the diversity of functions described for SRF in these organisms, the proteins display a high similarity at their MADS boxes, which are the main functional regions of the proteins.
1. Results cDNA clones coding for the putative A. franciscana SRF homologue were obtained after screening 500 000 clones of a cDNA library made from adults RNA (Palmero et al., 1988) with a probe derived from D. melanogaster SRF (Affolter et al., 1994). The 2361 nt long cDNA (EMBL Accession number AJ251270) coded for a 317 amino acids polypeptide that showed a strong similarity to the
Fig. 1. Comparison of the amino acid sequence of A. fransciscana SRF homologue (Af) to those of H. sapiens (Hs) and D. melanogaster (Dm) SRFs around the human Serl03 phosphorilation site, indicated by the asterisk. Dots indicate amino acids identical to those of A. franciscana shown above. Slashes indicate gaps introduced to increase the similarities. Numbers at the beginning and the end of each sequence indicate the position of the ®rst and last amino acids shown in this alignment on the complete amino acid sequence of each protein.
* Corresponding author. Tel.: 134-91-585-4626; fax: 134-91-585-4587. E-mail address: [email protected] (L. Sastre). 0925-4773/00/$ - see front matter q 2000 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0925-477 3(00)00386-5
230
M.-C. Casero, L. Sastre / Mechanisms of Development 96 (2000) 229±232
Fig. 2. In situ hybridization analyses of SRF expression in A. franciscana nauplii. A. franciscana nauplii cultured for 40 h were cut in 10 mm sections and hybridized with digoxigenin-labeled RNA probes corresponding to the antisense SRF strand (SRF1, panels A±C) or the sense strand (SRF2, panels D±F) as described by Escalante et al. (1995). The upper panel shows a picture of an untreated, unsectioned nauplius of the same developmental stage to facilitate the identi®cation of the structures. Panels A and D show longitudinal sections of the nauplii where the head is located towards the right side and the dorsal region to the top. Panels (B±F) show transversal sections of the anterior region. Symbols: a, anterior; d, dorsal; e, epidermis; f, foregut; g, gut; h, hindgut. Bar represents 200 mm.
MADS-box sequences of SRF from D. melanogaster (98% identity) (Affolter et al., 1994), humans (96%) (Norman et al., 1988) and D. discoideum (85%) (Escalante and Sastre, 1998). The identity also extended to two regions contiguous to the MADS-box, a short N-terminal and a 50 amino acid long C-terminal regions. Another small region of amino acid sequence similarity, not previously described, was found between A. franciscana amino acids 55±63, D. melanogaster amino acids 107±116 and human amino acids 95± 104 (Fig. 1). This region contains human Ser103, that has been described to be phosphorilated, in vitro and in vivo, by the protein kinase MCKII (Heidenreich et al., 1999). The tissue-speci®c expression of SRF in A. franciscana nauplii was determined by in situ hybridization using digoxigenin-labeled RNA probes (Fig. 2A±C). Sense probes from the same cDNA region were used as negative controls (Fig. 2D±F). A strong hybridization, speci®c for the antisense probe, was obtained in all ectodermal tissues, including the epidermal tissue and the terminal regions of the digestive tube (foregut and hindgut). No SRF expression was observed in the muscles, located in the central part of the antennae and surrounding the digestive tube (Fig. 2A,B). The spatial pattern of expression observed for SRF mRNA in A. franciscana is very different from those described in vertebrates and D. melanogaster. The only common feature seems to be the conservation of the expression in some ectodermal tissues: neuroectodermal tissues in vertebrates (Herdegen et al., 1997; Croissant et al., 1996), terminal tracheal and wing intervein regions in D. melanogaster (Affolter et al., 1994; Montagne et al., 1996) and all ectodermal cells in A. franciscana. The A. franciscana Actin 403 gene promoter has been described to contain a canonical SRF-binding site (Ortega
Fig. 3. In situ hybridization analyses of Actin 403 expression in A. franciscana nauplii. A. franciscana nauplii cultured for 40 h were cut in 10 mm sections and hybridized with ¯uorescein-labeled oligonucleotides 44 (5 0 -GGTGGCATCTTCACTCTTGGACATAAGCAG-3 0 ), complementary to the 3 0 untranslated region of Actin403 mRNA (panel A), or 11 (5 0 -CGAGACTTACTAAATCTTAGAAGACTGGTG-3 0 ), complementary to the 3 0 untranslated region of Actin205 mRNA (panel B), or with a digoxigenin-labeled RNA probe complementary to the 3 0 untranslated region of Actin403 mRNA (lanes C and D). Panels (A,B) show transversal sections of the anterior region of the nauplii. Panels (C,D) show longitudinal sections of the anterior and posterior region of the nauplii, respectively. Symbols: a, anterior; d, dorsal; e, epidermis; f, foregut; g, gut; h, hindgut; l, labrum. Bar represents 200 mm.
M.-C. Casero, L. Sastre / Mechanisms of Development 96 (2000) 229±232
231
mia is the activation of the encysted embryos, that are in a cryptobiotic stage. The amount of SRF mRNA expressed during development of A. franciscana encysted embryos was determined by Northern blot (Fig. 4A). The SRF cDNA clone used as probe hybridized with two RNAs of 18 and 1.8 kb. The amount of both RNAs remained constant during the period of embryonic development studied, from the encysted embryos (0 h) to ®rst instar nauplii (23 h). SRF binding activity was determined at different developmental stages by gel retardation assays. The results are shown in Fig. 4B. Naupliar nuclear extracts originated a retardation band that was speci®c for the SRF binding site. Nuclear extracts from encysted embryos produced a much weaker retardation band. These results show a clear induction of SRF activity during embryonic development, indicating a postranscriptional control of the expression and/or activity of this protein during A. franciscana embryonic development. Acknowledgements We are indebted to Dr Markus Affolter for the donation of the D. melanogaster SRF cDNA clone, to Drs Rosario Perona and Ricardo Escalante for critical reading of the manuscript and helpful discussions. This work has been supported by Grant PB95-0096 and PB98-0517 from the DireccioÂn General de EnsenÄanza Superior e InvestigacioÂn CientI®ca. References Fig. 4. Levels of SRF mRNA expression and serum response element (SRE)-binding activity during A. franciscana early development. Panel A: total RNA was obtained from A. franciscana encysted embryos either before (0 h) or after 4, 16, 20 or 23 h of development (lanes 0, 4, 16, 20 and 23, respectively). Fifteen micrograms of each RNA were analyzed on a 1.5% agarose-2.2 M Formaldehyde gel, transferred to nylon ®lters and hybridized to 32P-labeled A. franciscana SRF cDNA. The migration of the ribosomal RNAs used as markers is indicated at the right of the picture. Panel B: nuclear extracts were obtained from A. franciscana cryptobiotic embryos either untreated (cysts) or cultured for 20 h (nauplii). Thirty micrograms of nuclear extracts were incubated with the 32P-labeled oligonucleotide SRE (5 0 -ACATGACCATATAAGGTATTGCAGCT-3 0 ), either alone (lanes-) or in the presence of a 100-fold excess of the unlabeled oligonucleotides SRE, the CArG-mutated SRE* 5 0 -ACATGAACATACAAGGTATTGCAGCT-3 0 ) or the unrelated oligonucleotide Act (5 0 -CCAACATCATCACATGCACC-3 0 ) (lanes SRE, SRE* and Act, respectively), as previously described (Perona et al., 1997). Arrowheads indicate the migration of the SRE-speci®c retardation complexes.
et al., 1996). In situ hybridization experiments were performed using probes complementary to the 3 0 untranslated region of Actin403 mRNA. This gene was found to be expressed in the epidermis and the terminal regions of the digestive tube (foregut and hindgut) with a pattern of expression similar to that of the SRF homologue, in agreement with its transcriptional regulation by SRF (Fig. 3). An interesting aspect of transcriptional regulation in Arte-
Affolter, M., Montagne, J., Walldorf, U., Groppe, J., Kloter, U., LaRosa, M., Gehring, W.J., 1994. The Drosophila SRF homolog is expressed in a subset of tracheal cells and maps within a genomic region required for tracheal development. Development 120, 743±753. Arsenian, S., Weinhold, B., Oelgeschlager, M., Ruther, U., Nordheim, A., 1998. Serum response factor is essential for mesoderm formation during mouse embryogenesis. EMBO J. 17, 6289±6299. Belaguli, N.S., Schildmeyer, L.A., Schwartz, R.J., 1997. Organization and myogenic restricted expression of the murine serum response factor gene. A role for autoregulation. J. Biol. Chem. 272, 18222±18231. Croissant, J.D., Kim, J.H., Eichele, G., Goering, L., Lough, J., Prywes, R., Schwartz, R.J., 1996. Avian serum response factor expression restricted primarily to muscle cell lineages is required for alpha-actin gene transcription. Dev. Biol. 177, 250±264. Escalante, R., Sastre, L., 1998. A serum response factor homolog is required for spore differentiation in Dictyostelium. Development 125, 3801±3808. Escalante, R., GarcõÂa-SaÂez, A., Sastre, L., 1995. In situ hybridization analyses of Na K-ATPase alpha-subunit expression during early larval development of Artemia franciscana. J. Histochem. Cytochem. 43, 391±399. Heidenreich, O., Neininger, A., Schratt, C., Zinck, R., Cahill, M.A., Engel, K., Kotlyarov, A., Kraft, R., Kostka, S., Gaestel, M., Nordheim, A., 1999. MAPKAP kinase 2 phosphorylates serum response factor in vitro and in vivo. J. Biol. Chem. 274, 14434±14443. Herdegen, T., Blume, A., Buschmann, T., Georgakopoulos, E., Winter, C., Schmid, W., Hsieh, T.F., Zimmermann, M., Gass, P., 1997. Expression of activating transcription factor-2, serum response factor and cAMP/ Ca response element binding protein in the adult rat brain following
232
M.-C. Casero, L. Sastre / Mechanisms of Development 96 (2000) 229±232
generalized seizures, nerve ®ber lesion and ultraviolet irradiation. Neuroscience 81, 199±212. Montagne, J., Groppe, J., Guillemin, K., Krasnow, M.A., Gehring, W.J., Affolter, M., 1996. The Drosophila serum response factor gene is required for the formation of intervein tissue of the wing and is allelic to blistered. Development 122, 2589±2597. Norman, C., Runswick, M., Pollock, R., Treisman, R., 1988. Isolation and properties of cDNA clones encoding SRF, a transcription factor that binds to the c-fos serum response element. Cell 55, 989±1003.
Ortega, M.A., DõÂaz-Guerra, M., Sastre, L., 1996. Actin gene structure in two Artemia species A. franciscana and A. parthenogenetica. J. Mol. Evol. 43, 224±235. Palmero, I., Renart, J., Sastre, L., 1988. Isolation of cDNA clones coding for mitochondrial 16S ribosomal RNA from the crustacean Artemia. Gene 68, 239±248. Perona, R., Montaner, S., Saniger, L., SaÂnchez-PeÂrez, I., Bravo, R., Lacal, J.C., 1997. Activation of the nuclear factor-kB by Rho CDC42, and Rac-1 proteins. Genes Dev. 11, 463±475.