RASA1 expression highlights Z/W dosage dynamics and gonadal development in chickens

All identified genes on the avian W chromosome have homologous counterparts on the Z chromosome, with protein-coding genes showing over 90% homology. These W-linked genes are typically dose-sensitive and conserved, ensuring balanced expression between sexes during development. This study explores the sequence characteristics, expression patterns, and potential functions of the RASA1 gene in chicken embryos. In gonads, RASA1-Z was found to be more highly expressed in males, but total mRNA levels (RASA1-C) were higher in females due to RASA1-W compensation. However, RASA1 protein levels were significantly higher in males, suggesting limited contribution of RASA1-W. Knockdown of RASA1-Z reduced both mRNA and protein levels, whereas overexpression of RASA1-W increased mRNA but not protein levels. Sex reversal experiments showed no significant changes in RASA1 expression, indicating it is not involved in gonadal sex differentiation. However, higher expression in the left female gonad suggests a role in gonadal development. Functional studies using CCK8 proliferation assays revealed that RASA1-Z promotes cell proliferation, while RASA1-W has minimal impact. This study indicates that RASA1 primarily functions in cell proliferation and angiogenesis rather than sex differentiation, with RASA1-W contributing to transcript balance but not protein output.