Identification of differentially expressed genes involved in the regression and development of the chicken Mullerian duct

Mullerian ducts of male chickens undergo regression around day 12 of incubation, but the underlining mechanisms remain unclear. The purpose of this study was to identify factors that contribute to regression of the Mullerian duct in the chicken. We first employed annealing control primer-based RT-PCR to screen candidate genes differentially expressed in the Mullerian ducts between male and female. Four differentially expressed genes (MSX2, GAL10, VCP and PLCH1) were partially sequenced. The expression of mRNA of the latter genes and MSX1 in the male and female Mullerian ducts were compared at 7.5, 8 and 9 days of incubation using semi-quantitative RT-PCR. The results indicated that both MSX1 and MSX2 mRNA was highly expressed in the male Mullerian duct at day 9 of incubation, whereas, PLCH1 mRNA was lower in the male duct at day 9 of incubation compared to that of the female duct. Although VCP mRNA was expressed in both left and right female Mullerian ducts, no expression was detected in the male duct. Whole mount in situ hybridyzation analysis showed that the expression of MSX1 and MSX2 mRNA were localized specifically in the mesenchymal cells of the male Mullerian duct at day 9 of incubation. In contrast, VCP mRNA expression was observed in both mesenchymal and epithelial cells of the female Mullerian duct but not detected in the male duct. These results suggest that both up-regulation of MSX1 and MSX2 mRNA expression is involved in the regression of the Mullerian duct in male chicken embryo, whereas VCP expression is involved in development of the female duct.