Meiosis initiation is a crucial step for the production of haploid gametes, which occurs from anterior to posterior in fetal ovaries. The asynchrony of the transition from mitosis to meiosis results in heterogeneity in the female germ cell populations, which limits the studies of meiosis initiation and progression at a higher resolution level. To dissect the process of meiosis initiation, we investigated the transcriptional profiles of 19 363 single germ cells collected from E12.5, E14.5, and E16.5 mouse fetal ovaries. Clustering analysis identified seven groups and defined dozens of corresponding transcription factors, providing a global view of cellular differentiation from primordial germ cells toward meiocytes. Furthermore, we explored the dynamics of gene expression within the developmental trajectory with special focus on the critical state of meiosis. We found that meiosis initiation occurs as early as E12.5 and the cluster of oogonia_4 is the critical state between mitosis and meiosis. Our data provide key insights into the transcriptome features of peri‐meiotic female germ cells, which offers new information not only on meiosis initiation and progression but also on screening pathogenic mutations in meiosis‐associated diseases.

中文翻译：

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单细胞 RNA 测序揭示了早期女性生殖细胞发育的格局

减数分裂起始是产生单倍体配子的关键步骤，单倍体配子在胎儿卵巢中从前到后发生。从有丝分裂到减数分裂的不同步导致雌性生殖细胞群的异质性，这限制了在更高分辨率水平上对减数分裂起始和进展的研究。为了剖析减数分裂起始的过程，我们研究了从 E12.5、E14.5 和 E16.5 小鼠胎儿卵巢收集的 19 363 个单个生殖细胞的转录谱。聚类分析确定了七组并定义了数十种相应的转录因子，提供了从原始生殖细胞到性母细胞的细胞分化的全局视图。此外，我们探索了发育轨迹中基因表达的动态，特别关注减数分裂的临界状态。我们发现减数分裂的开始最早发生在 E12.5 并且 oogonia_4 簇是有丝分裂和减数分裂之间的临界状态。我们的数据提供了对减数分裂周围雌性生殖细胞转录组特征的关键见解，这不仅提供了关于减数分裂起始和进展的新信息，还提供了减数分裂相关疾病中筛选致病突变的新信息。