Differential transcriptomic investigation of embryonic pectoral muscle revealed more intense myogenic processes in Shitou Goose than Wuzong Goose

Embryonic stages before hatching is crucial for poultry muscle development, which determines muscle mass in adulthood. In this study, we aim to uncover embryonic pectoral muscle development distinctions between Wuzong (WZE, small) and Shitou (STE, large) goose (two indigenous goose breeds in Guangdong Province, China, with different body size) at Embryonic day 15 (E15), 23 (E23) and 1st day of hatching (P1) and gain further insight into the regulatory mechanisms behind it. The results showed that STE had significantly higher myofiber density during E15-P1 and had significantly higher myofiber diameter at E15 than WZE. By utilizing RNA-seq analysis, 19507 genes were detected and a number of differential expressed genes (DEGs) were identified. It was found that gene expression distinctions begin increasing between breeds since E23, and WZE has different gene expression profiles with STE. Further, all the myogenic genes (myo-genes) were only found by selecting myogenic biological processes from GO analysis of DEGs in comparison between breeds at E15 or between E15 and E23 in two breeds, indicating that myo-genes involved in E15 may influence distinct pectoral muscle development characteristics between WZE and STE. The RT-qPCR results were well in consistent with RNA-seq analysis. 4 muscle structure protein coded genes (Myl2, Myl3, Tnni2 and Tnnc2 and 3 other functional genes (Cav3, Cacna1s and Nos1) were found in predicted interaction network. These functional genes may interact with muscle structure protein coded genes to regulate embryonic pectoral muscle development distinctions in WZE and STE.