Center of Excellence for Marine Bioenvironment and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan.
Biol Reprod. 2013 Jun 13;88(6):150. doi: 10.1095/biolreprod.112.105536. Print 2013 Jun.
Meiosis is an essential mechanism of gametogenesis for all sexually reproducing species. In vertebrates, one conserved aspect of sex differentiation is that female embryonic germ cells enter meiosis earlier than male germ cells. In some lower vertebrates, female germ cells proliferate prior to entering meiosis, whereas male cells remain in mitotic arrest. Protandrous black porgy fish, Acanthopagrus schlegelii, have a dramatic life cycle involving a characteristic sex change. Black porgy are functional males for their first and second spawning seasons, but approximately half of the fish transform into females during their third year. We cloned the black porgy homologs of dosage suppressor of mck1 homolog (dmc1) and synaptonemal complex protein 3 (sycp3), and examined their expression profiles as well as those of cytochrome P450 family 26 genes (cyp26: cyp26a and cyp26b), retinaldehyde dehydrogenases (raldh: raldh2 and raldh3), retinoic acid receptors (rars: raralpha, rarbeta, rargamma, and rargammab), retinoid X receptors (rxrs: rxralpha, rxrbeta, and rxrgamma) and deleted azoospermia-like (dazl) during gonadal sex differentiation by RT-PCR, quantitative RT-PCR, and immunohistochemistry. Our results show that during gonadal development, germ cells located in ovarian tissue proceed into meiosis earlier than germ cells in testicular tissue. Furthermore, treatment with estradiol-17beta, which induced cyp26 expression, blocked dazl and raldh expression and reduced the expression of rars, rxrs, dmc1, and sycp3. This unique model therefore suggests that the temporal differences in meiosis initiation between females and males are conserved during gonadal sex differentiation in hermaphroditic vertebrates.
减数分裂是所有有性生殖物种配子发生的重要机制。在脊椎动物中，性别分化的一个保守方面是雌性胚胎生殖细胞比雄性生殖细胞更早进入减数分裂。在一些较低等的脊椎动物中，雌性生殖细胞在进入减数分裂之前增殖，而雄性细胞仍然处于有丝分裂阻滞状态。雄性先熟的黑鲷鱼，Acanthopagrus schlegelii，具有一个显著的生命周期，涉及到一个特征性的性别转换。黑鲷鱼在它们的第一和第二个产卵季节是功能性的雄性，但大约有一半的鱼在它们的第三年变成雌性。我们克隆了黑鲷鱼剂量抑制因子 mck1 同源物（dmc1）和联会复合体蛋白 3（sycp3）的同源物，并检查了它们的表达谱以及细胞色素 P450 家族 26 基因（cyp26：cyp26a 和 cyp26b）、视黄醛脱氢酶（raldh：raldh2 和 raldh3）、视黄酸受体（rars：raralpha、rarbeta、rargamma 和 rargammab）、视黄醇 X 受体（rxrs：rxralpha、rxrbeta 和 rxrgamma）和缺失的无精子症样（dazl）在通过 RT-PCR、定量 RT-PCR 和免疫组织化学在性腺性别分化过程中的表达。我们的结果表明，在性腺发育过程中，位于卵巢组织中的生殖细胞比位于睾丸组织中的生殖细胞更早进入减数分裂。此外，用雌二醇-17β处理，诱导 cyp26 的表达，阻断了 dazl 和 raldh 的表达，并降低了 rars、rxrs、dmc1 和 sycp3 的表达。因此，这个独特的模型表明，在雌雄同体脊椎动物的性腺性别分化过程中，雌性和雄性之间减数分裂起始的时间差异是保守的。
