Abstract
Male gametes are generated through a specialised differentiation pathway involving a series of developmental transitions that are poorly characterised at the molecular level. Here, we use droplet-based single-cell RNA-Sequencing to profile spermatogenesis in adult animals and at multiple stages during juvenile development. By exploiting the first wave of spermatogenesis, we both precisely stage germ cell development and enrich for rare somatic cell-types and spermatogonia. To capture the full complexity of spermatogenesis including cells that have low transcriptional activity, we apply a statistical tool that identifies previously uncharacterised populations of leptotene and zygotene spermatocytes. Focusing on post-meiotic events, we characterise the temporal dynamics of X chromosome re-activation and profile the associated chromatin state using CUT&RUN. This identifies a set of genes strongly repressed by H3K9me3 in spermatocytes, which then undergo extensive chromatin remodelling post-meiosis, thus acquiring an active chromatin state and spermatid-specific expression.
Highlights
Male gametes are generated through a specialised differentiation pathway involving a series of developmental transitions that are poorly characterised at the molecular level
Based on the combination of cell-types, the seminiferous epithelium is classified into 12 distinct stages in mouse, and tubules of all stages exist in adult testes (Fig. 1a, b, Supplementary Fig. 1a)
Intermediate spermatogonia (In) contrast to most developmental differentiation processes which require the profiling of cellular populations at several time-points[58,59], spermatogenesis occurs continuously, with all intermediate cell-types present in adult
Summary
Male gametes are generated through a specialised differentiation pathway involving a series of developmental transitions that are poorly characterised at the molecular level. Correspondence and requests for materials should be addressed to Spermatogenesis is a tightly regulated developmental process that occurs in the epithelium of seminiferous tubules in the testis and ensures the continuous production of mature sperm cells In the mouse, this unidirectional differentiation process initiates with the division of spermatogonial stem cells (SSC) to form a pair or connected chain of undifferentiated spermatogonia (Apaired and Aaligned)[1]. To confidently identify and label cell populations throughout the developmental trajectory, we profile cells from the first wave of spermatogenesis, where cells have only progressed to a defined developmental stage This allows us to unambiguously identify the most mature cell-type by comparison with adult and to characterize the dynamic differentiation processes of somatic cells and spermatogonia that are enriched in juvenile testes
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