Gene Expression Profiling Reveals Potential Players of Sex Determination and Asymmetrical Development in the Chicken Embryo Gonads. Gallus gallus

Despite notable progress in recent years, the understanding of chicken genetic control of gonadal sex differentiation and asymmetrical ovariogenesis during embryonic development remains incomplete. This study aimed to identify potential key genes and speculate mechanisms associated with ovary and testis development by analyzing Pacbio and Illumina sequencing results of embryonic chicken gonads at the initiation of sexual differentiation (E4.5, E5.5, and E6.5). Pacbio sequencing detected 328 and 233 significantly up-regulated transcripts in females and males respectively at E4.5, among them 232 were novel. Illumina sequencing detected 95, 296 and 445 DEGs at E4.5, E5.5, and E6.5, respectively. Moreover, both of sexes showed asymmetrical expression in gonads, and more DEGs were detected on the left side. There were 12 DEGs involved in cell proliferation are shared in left gonads of males and females. GO analysis suggested that coagulation pathways may be involved in the degradation of the right gonad in females and blood oxygen transport pathways may be involved in preventing the degradation of the right gonad in males. These results provide a comprehensive expression profiling of chicken embryo gonads at the initiation of sexual differentiation, which can be as a theoretical basis for further understanding the mechanism of bird sex determination and its evolutionary process.