The protein expression of zona pellucida B1, B2, and C in turkey and broiler breeder hens
Steed, Joshua Ryan
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The ovulated ovum in avian species is surrounded by a protein layer called the inner perivitelline layer (IPVL). The IPVL contains the zona pellucida (ZP) family of proteins, and in mammalian species one or more of the ZP proteins serve as the key component(s) of the sperm receptor. Sperm binding to sperm receptors located at the germinal disc (GD) region of the ovulated ovum initiates the biological steps necessary for optimum fertilization in avian species, and the amount of sperm binding at the GD reflects female fertility potential. In both chicken and turkey hens, six ZP proteins genes have been identified and hepatic produced ZPB1 and granulosa cell produced ZPB2 and ZPC appear to play key roles in sperm binding based on mRNA expression results. The goal of the current research was to determine if previously reported differences in mRNA expression in genetic lines of turkey hens and broiler breeder hens are translated to the protein level. Although ZPB2 protein expression significantly decreases as broiler breeder follicles mature from prehierarchical to hierarchical follicles, the expression of ZPB2 in the IPVL is greater in the GD region compared to nongerminal disc (NGD) region in both turkey and broiler breeder hens as mRNA expression indicated. However, protein expression of ZPB1 and ZPC in the IPVL of two genetic lines (E, high fertility and F, low fertility) of turkey hens was opposite of mRNA expression indications. ZPC protein expression was higher in E line IPVL, and ZPC expression was not different between GD and NGD IPVL regions which also disagreed with mRNA expression indications. The results indicate that mRNA expression of ZP proteins at their site of synthesis in different genetic lines of turkey and broiler breeder hens often do not directly correlate with IPVL protein expression of these proteins. In addition, the greater protein concentration of ZPB2 in the GD region compared to the NGD region suggests that this protein may be a critical component of the sperm receptor and could serve as a genetic selection marker for female fertility.