A comprehensive transcriptional profiling of developing gonads reveals the role of TGFβ signaling in female gonadal asymmetry in chickens

Asymmetrical gonadal development is an intriguing phenomenon observed in the majority of female birds. In chickens, the left gonad of female embryos develops into a functional ovary, while the right gonad undergoes degeneration during embryogenesis. This sexually dimorphic trait is primarily induced by the spatial differential expression of the paired like homeodomain 2 (PITX2) gene. However, a comprehensive understanding of the transcriptional profile of the developing gonads during asymmetric development is still lacking. To elucidate the molecular mechanism of asymmetric gonadal development in chickens, we compared the transcriptomes between left and right gonads of female chickens using bulk- and single cell-RNA sequencing (scRNA-seq) approaches. Our bulk RNA-seq analysis of the female chicken gonads at E5 (HH26), E6.5 (HH30), E8 (HH34), and E9.5 (HH36) revealed significant differential gene expression between the left and right female chicken gonads, particularly in signaling pathways, cell cycle, and metabolic processes. Moreover, scRNA-seq analysis revealed that coelomic epithelial, interstitial, and pre-granulosa cells of the left gonads at E5 show a highly proliferative status compared to the right gonad, contributing to the asymmetric gonadal cell proliferation, which may be regulated by the transforming growth factor beta (TGFβ) signaling pathway. Our findings demonstrate that dynamic cell-type-specific transcriptional profiles during embryogenesis play a vital role in the asymmetric gonadal development of female chickens.