Bhattacharya Indrashis, Sharma Partigya, Purohit Shriya, Kothiyal Sachin, Das Moitreyi, Banerjee Arnab
Department of Zoology, HNB Garhwal University, A Central University, Srinagar Campus, Uttarakhand, India.
Department of Biotechnology, Goa University, Taleigao, India.
Front Cell Dev Biol. 2022 Mar 16;10:833759. doi: 10.3389/fcell.2022.833759. eCollection 2022.
Germ cells (Gc) propagate the genetic information to subsequent generations. Diploid (2n) Gc get transformed to specialized haploid (n) gametes by mitotic and meiotic divisions in adult gonads. Retinoic acid (RA), an active derivative of vitamin A (retinol), plays a critical role in organ morphogenesis and regulates the meiotic onset in developing Gc. Unlike ovaries, fetal testes express an RA-degrading enzyme CYP26B1, and thereby, male Gc fail to enter into meiosis and instead get arrested at G/G stage, termed as gonocytes/pro-spermatogonia by embryonic (E) 13.5 days. These gonocytes are transformed into spermatogonial stem/progenitor cells after birth (1-3 days of neonatal age). During post-natal testicular maturation, the differentiating spermatogonia enter into the meiotic prophase under the influence RA, independent of gonadotropic (both FSH and LH) support. The first pulse of RA ensures the transition of undifferentiated type A spermatogonia to differentiated A spermatogonia and upregulates STRA8 expression in Gc. Whereas, the second pulse of RA induces the meiotic prophase by augmenting MEIOSIN expression in differentiated spermatogonia B. This opinion article briefly reviews our current understanding on the RA-driven spermatogonial differentiation in murine testes.
生殖细胞（Gc）将遗传信息传递给后代。二倍体（2n）生殖细胞在成年性腺中通过有丝分裂和减数分裂转化为特化的单倍体（n）配子。视黄酸（RA）是维生素A（视黄醇）的活性衍生物，在器官形态发生中起关键作用，并调节发育中的生殖细胞的减数分裂起始。与卵巢不同，胎儿睾丸表达一种RA降解酶CYP26B1，因此，雄性生殖细胞无法进入减数分裂，而是在G/G期停滞，在胚胎（E）13.5天时被称为生殖母细胞/前精原细胞。这些生殖母细胞在出生后（新生儿期1 - 3天）转化为精原干细胞/祖细胞。在出生后睾丸成熟过程中，分化中的精原细胞在RA的影响下进入减数分裂前期，独立于促性腺激素（FSH和LH）的支持。RA的第一个脉冲确保未分化的A型精原细胞向分化的A型精原细胞转变，并上调生殖细胞中STRA8的表达。而RA的第二个脉冲通过增强分化的B型精原细胞中MEIOSIN的表达来诱导减数分裂前期。这篇观点文章简要回顾了我们目前对RA驱动的小鼠睾丸精原细胞分化的理解。
