A W-linked DM-domain gene, DM-W, participates in primary ovary development in Xenopus laevis.
In the XX/XY sex-determining system, the Y-linked SRY genes of most mammals and the DMY/Dmrt1bY genes of the teleost fish medaka have been characterized as sex-determining genes that trigger formation of the testis. However, the molecular mechanism of the ZZ/ZW-type system in vertebrates, including the clawed frog Xenopus laevis, is unknown. Here, we isolated an X. laevis female genome-specific DM-domain gene, DM-W, and obtained molecular evidence of a W-chromosome in this species. The DNA-binding domain of DM-W showed a strikingly high identity (89%) with that of DMRT1, but it had no significant sequence similarity with the transactivation domain of DMRT1. In nonmammalian vertebrates, DMRT1 expression is connected to testis formation. We found DMRT1 or DM-W to be expressed exclusively in the primordial gonads of both ZZ and ZW or ZW tadpoles, respectively. Although DMRT1 showed continued expression after sex determination, DM-W was expressed transiently during sex determination. Interestingly, DM-W mRNA was more abundant than DMRT1 mRNA in the primordial gonads of ZW tadpoles early in sex determination. To assess the role of DM-W, we produced transgenic tadpoles carrying a DM-W expression vector driven by approximately 3 kb of the 5'-flanking sequence of DM-W or by the cytomegalovirus promoter. Importantly, some developing gonads of ZZ transgenic tadpoles showed ovarian cavities and primary oocytes with both drivers, suggesting that DM-W is crucial for primary ovary formation. Taken together, these results suggest that DM-W is a likely sex (ovary)-determining gene in X. laevis.
Yoshimoto
Shin
S
Department of Bioscience, School of Science, Kitasato University, 1-15-1 Kitasato, Sagamihara, Kanagawa 228-8555, Japan.
Okada
Ema
E
Umemoto
Hirohito
H
Tamura
Kei
K
Uno
Yoshinobu
Y
Nishida-Umehara
Chizuko
C
Matsuda
Yoichi
Y
Takamatsu
Nobuhiko
N
Shiba
Tadayoshi
T
Ito
Michihiko
M
D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D016678:Genome / Q000235:genetics; D005838:Genotype; D007814:Larva / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D010053:Ovary; D011401:Promoter Regions, Genetic; D012730:Sex Chromosomes / Q000235:genetics*; D019849:Sex Determination Processes; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014982:Xenopus laevis / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism
C110547:DMRT1 protein; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; C102284:Myc protein, Drosophila; D014157:Transcription Factors