Testis morphogenesis and fetal Leydig cell development are mediated through ERK signaling activated by platelet derived growth factor receptor alpha

Platelet derived growth factor receptor alpha (Pdgfra) plays a crucial role in the morphogenesis and differentiation of the fetal testis, but the molecular signaling involved in these processes remains unclear. Here, we use XY Pdgfra-null knock-in (KI) gonads to investigate the molecular mechanisms underlying Pdgfra-mediated testis cord formation and development of fetal Leydig cells (FLCs). The extracellular signal-regulated kinase (ERK) pathway, a well-known mitogen-activated protein kinase signaling pathway, was significantly inhibited in XY Pdgfra KI gonads, suggesting that ERK signaling is activated downstream of PDGFRA. Using ex vivo whole-organ culture, small interfering RNA (siRNA) cell culture methods, transwell assays and a genetic mouse model to disrupt ERK signaling in gonadal cells, we found that the ERK pathway promoted testis cord formation via early growth response 1 (Egr1)-mediated cell migration and regulated the expression of steroidogenic enzymes in FLCs via activating the transcription factor cAMP responsive element binding protein 1 (CREB; official name CREB1). These findings highlight the significance of PDGFRA and its downstream signaling in fetal testis morphogenesis and cellular differentiation, thus providing insights into the etiology of and potential therapeutic targets for disorders related to gonadal development.