Cloning and expression analysis of androgen receptor gene in chicken embryogenesis

We cloned a full-length androgen receptor (AR) cDNA from chicken (Gallus gallus) gonads. The cDNA sequence has an open reading frame of 2109 bp encoding 703 amino acids. The chicken AR (cAR) shares high homology with ARs from other species in its amino acid sequences, in particular DNA binding domain (DBD) and ligand binding domain (LBD). RT-PCR analysis revealed that cAR mRNA is expressed in several embryonic tissues of both sexes, and relatively higher expression was observed in left ovary compared with testis. The immunoreactive signal of AR was co-localized within the ovarian cell nucleus, while such nuclear localization was not detected in those of testis. To get insight on the possible role of androgen-AR signaling during gonadal development, non-steroidal AR antagonist, flutamide, was administrated in ovo. The treatment induced the disorganization of sex cords in ovarian cortex at day 12 of incubation. The effect was restored by testosterone co-treatment, implying the possibility that AR mediated signaling may be involved in ovarian morphogenesis. Furthermore, co-treatment of flutamide with estradiol-17beta (E2) also restored the phenotype, suggesting androgen-AR signaling might activate aromatase expression that is necessary for estrogen synthesis. These findings suggest androgen-AR signaling might contribute to chicken embryonic ovarian development.