Oocyte apoptosis during the transition from ovary-like tissue to testes during sex differentiation of juvenile zebrafish.
Large numbers of apoptotic early diplotene oocytes were observed during the transition from ovary-like undifferentiated gonadal tissue to testes during sex differentiation in presumptive males of the zebrafish (Danio rerio). The percentage of terminal-deoxynucleotidyl-transferase-mediated dUTP nick-end labelling (TUNEL)-positive apoptotic oocytes in the gonads of presumptive males was approximately eight- to 12-fold higher than in genetic all-females. By 29 days post-hatching, all oocytes had disappeared from the gonads of presumptive males. In these males, we also observed apoptotic somatic cells in the ovarian cavity between 23 and 35 days post-hatching. Therefore, the disappearance of oocytes and the decomposition of the ovarian cavity caused by apoptosis during sex differentiation were male-specific events. In genetic all-females, apoptosis in a proportion of early diplotene oocytes was found in the undifferentiated gonads at 15-19 days post-hatching, probably as a result of programmed oocyte loss during ovarian development. These findings suggest that oocyte apoptosis is the mechanism of testicular and ovarian differentiation in zebrafish.
Uchida
Daisuke
D
Graduate School of Integrated Science, Yokohama City University, Seto, Kanazawa-ku, Yokohama 236-0027, Japan.
Yamashita
Michiaki
M
Kitano
Takeshi
T
Iguchi
Taisen
T
D000818:Animals; D017209:Apoptosis; D002454:Cell Differentiation; D005260:Female; D020287:In Situ Nick-End Labeling; D008297:Male; D009865:Oocytes / Q000166:cytology*; D010053:Ovary / Q000196:embryology*; D012733:Sex Differentiation / Q000235:genetics; D013737:Testis / Q000196:embryology*; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics