Deciphering the single-cell transcriptomic atlas of donkey (Equus asinus) gonad development in early gestation

In donkey reproduction, the extended reproductive cycle is a pivotal factor contributing to the low reproductive rate. Gonadal development represents a highly complex biological process that involves sex determination and subsequent progression toward ovarian maturation. Currently, the mechanisms underlying ovarian development in donkeys remain poorly understood. To address this gap, we constructed single-cell transcriptome maps of the gonads of donkey embryos during pregnancy at four and eight weeks, thereby identifying the major cell types involved. During development, the morphology of the ovary undergoes significant changes, gradually transitioning from an initial long cylindrical shape to an oval form. Notably, differences exist in the cell type composition between the two ovarian tissues. Additionally, we observed variations in germ-cell-related genes, including DDX4, DAZL, POU5F1, and NANOG, which regulate the dynamic differentiation of germ cells across the two tissues. Cell communication interaction analysis uncovered variations in the signaling networks of TGF-β, AMH, BMP, and GDF associated with embryonic development in the two tissues. Furthermore, we examined functional distinctions in the epithelial cells of the two tissues and assessed the expression levels of genes linked to granulosa cells, revealing that granulosa cells likely originated from ovarian epithelial cells during early gestation. Collectively, this study elucidated the molecular characteristics of ovarian tissue transcription during early gestation, thereby facilitating further investigation into genetic markers and gene regulatory networks associated with ovarian development. This may provide valuable insights for research on reproductive disorders and genetic breeding.