mRNA and protein expression levels of four candidate genes for ear size in Erhualian and Large White pigs

Porcine ear size is an important characteristic for distinguishing among pig breeds. In a previous genome-wide association study of porcine ear size, LEM domain-containing 3 (LEMD3), methionine sulfoxide reductase B3 (MSRB3), high mobility group AT-hook 2 (HMGA2), and Wnt inhibitory factor 1 (WIF1) were implicated as important candidate genes for ear size. This study investigated the expression levels of four candidate genes for ear size in Erhualian and Large White pigs. Ten Erhualian pigs with large ears and eight Large White pigs with small ears at 60 days of age were examined. The mRNA expression levels of the four candidate genes were quantified by real-time polymerase chain reaction. WIF1 mRNA expression was significantly higher in Large White than in Erhualian pigs (P < 0.05), whereas the expression levels of the other three genes were not significantly different between the two breeds. The protein expression levels of the four genes were analyzed using western blot. WIF1 protein expression was significantly higher in Large White than in Erhualian pigs (P < 0.01), whereas MSRB3 protein expression was significantly higher in Erhualian than in Large White pigs (P < 0.05). There were no significant differences between the two breeds in residual protein expression. These results suggest that WIF1 is the main causal gene for ear size in pigs.