Chicken hemogen homolog is involved in the chicken-specific sex-determining mechanism

Using a comprehensive transcriptome analysis, a Z chromosome-linked chicken homolog of hemogen (cHEMGN) was identified and shown to be specifically involved in testis differentiation in early chicken embryos. Hemogen [Hemgn in mice, EDAG (erythroid differentiation-associated gene protein) in humans] was recently characterized as a hematopoietic tissue-specific gene encoding a transcription factor that regulates the proliferation and differentiation of hematopoietic cells in mammals. In chicken, cHEMGN was expressed not only in hematopoietic tissues but also in the early embryonic gonad of male chickens. The male-specific expression was identified in the nucleus of (pre)Sertoli cells after the sex determination period and before the expression of SOX9 (SRY-box 9). The expression of cHEMGN was induced in ZW embryonic gonads that were masculinized by aromatase inhibitor treatment. ZW embryos overexpressing cHEMGN, generated by infection with retrovirus carrying cHEMGN, showed masculinized gonads. These findings suggest that cHEMGN is a transcription factor specifically involved in chicken sex determination.