Transcriptomic investigation of embryonic pectoral muscle reveals increased myogenic processes in Shitou geese compared to Wuzong geese

Embryonic stages before birth are crucial for poultry muscle development, as this determines muscle mass in adulthood. This study characterised the distinction in embryonic pectoral muscle development between Wuzong (WZE, small) and Shitou (STE, large) geese (two indigenous goose breeds in Guangdong Province, China) at embryonic days 15 (E15), 23 (E23) and the day of hatching (P1) to gain insights into the regulatory mechanisms of muscle development.The results showed that STE had significantly higher myofibre density during E15-P1 and had significantly larger myofibre diameter at E15 than WZE. By RNA-sequencing analysis, 19507 genes were detected, and 7121 differentially expressed genes (DEGs) were identified.Gene expression distinctions between breeds began increasing from E23, and WZE had different gene expression profiles compared to STE. A GO analysis of DEGs indicated that myo-genes involved at E15 may influence distinct pectoral muscle development characteristics between WZE and STE. The RT-qPCR results were consistent with the RNA-sequencing (RNA-seq) analysis. Four muscle structure protein coding genes (<i>MYL2, MYL3, TNNI2</i> and <i>TNNC2</i> and three other functional genes (<i>CAV3, CACNA1S</i> and <i>NOS1</i>) were identified in a predicted interaction network. These functional genes may interact with muscle structural protein coding genes to regulate embryonic pectoral muscle development in WZE and STE geese.The study revealed that STE and WZE had divergent embryonic pectoral muscle development patterns and these differences may begin before E15. Embryonic stages before birth are crucial for poultry muscle development, as this determines muscle mass in adulthood. This study characterised the distinction in embryonic pectoral muscle development between Wuzong (WZE, small) and Shitou (STE, large) geese (two indigenous goose breeds in Guangdong Province, China) at embryonic days 15 (E15), 23 (E23) and the day of hatching (P1) to gain insights into the regulatory mechanisms of muscle development. The results showed that STE had significantly higher myofibre density during E15-P1 and had significantly larger myofibre diameter at E15 than WZE. By RNA-sequencing analysis, 19507 genes were detected, and 7121 differentially expressed genes (DEGs) were identified. Gene expression distinctions between breeds began increasing from E23, and WZE had different gene expression profiles compared to STE. A GO analysis of DEGs indicated that myo-genes involved at E15 may influence distinct pectoral muscle development characteristics between WZE and STE. The RT-qPCR results were consistent with the RNA-sequencing (RNA-seq) analysis. Four muscle structure protein coding genes (<i>MYL2, MYL3, TNNI2</i> and <i>TNNC2</i> and three other functional genes (<i>CAV3, CACNA1S</i> and <i>NOS1</i>) were identified in a predicted interaction network. These functional genes may interact with muscle structural protein coding genes to regulate embryonic pectoral muscle development in WZE and STE geese. The study revealed that STE and WZE had divergent embryonic pectoral muscle development patterns and these differences may begin before E15.