In mammals, male gonocytes are derived from primordial germ cells during embryogenesis, enter a period of mitotic proliferation, and then become quiescent until birth. After birth, the gonocytes proliferate and migrate from the center of testicular cord toward the basement membrane to form the pool of spermatogonial stem cells (SSCs) and establish the SSC niche architecture. However, the molecular mechanisms underlying gonocyte proliferation, migration and differentiation are largely unknown. Cyclin A2 is a key component of the cell cycle and required for cell proliferation. Here, we show that cyclin A2 is required in mouse male gonocyte development and the establishment of spermatogenesis in the neonatal testis. Loss of cyclin A2 function in embryonic gonocytes by targeted gene disruption affected the regulation of the male gonocytes to SSC transition, resulting in the disruption of SSC pool formation, imbalance between SSC self-renewal and differentiation, and severely abnormal spermatogenesis in the adult testis.

在哺乳动物中，雄性生殖细胞在胚胎发生过程中来源于原始生殖细胞，进入有丝分裂增殖期，然后进入静止状态直至出生。出生后，生殖细胞增殖并从睾丸索中心向基底膜迁移，形成精原干细胞 (SSC) 池并建立 SSC 生态位结构。然而，生殖细胞增殖、迁移和分化的分子机制在很大程度上是未知的。细胞周期蛋白 A2 是细胞周期的关键组成部分，是细胞增殖所必需的。在这里，我们表明细胞周期蛋白 A2 在小鼠雄性生殖细胞发育和新生儿睾丸中精子发生的建立中是必需的。