Identification of relevant differential genes to the divergent devel-opment of pectoral muscle in ducks by transcriptomic analysis.

Objective The objective of this study was to identify candidate genes that play im-portant roles in skeletal muscle development in ducks. Methods In this study, we investigated the transcriptional sequencing of embryonic pectoral muscles from two specialized line LCA and LCC ducks which were devel-oped from Liancheng White ducks (female) and Cherry Valley ducks (male) F6 hybrid population. In addition, prediction of target genes for the differentially expressed mRNAs was conducted and the enriched gene ontology (GO) terms and Kyoto En-cyclopedia of Genes and Genomes (KEGG) signaling pathways were further analyzed. Finally, a protein-to-protein interaction (PPI) network was analyzed by using the tar-get genes to gain insights into their potential functional association. Results A total of 1428 differentially expressed genes (DEGs) with 762 being up-regulated genes and 666 being down-regulated genes in pectoral muscle of LCA and LCC ducks identified by RNA-seq (p < 0.05). Meanwhile, 23 GO terms in the down-regulated genes and 75 GO terms in up-regulated genes were significantly en-riched (p < 0.05). Furthermore, the top 5 most enriched pathways were ECM-receptor interaction, fatty acid degradation, pyruvate degradation, PPAR signaling pathway, and glycolysis/gluconeogenesis. Finally, the candidate genes including Integrin b3 (Itgb3), Pyruvate kinase M1/2 (Pkm), Insulin-like growth factor 1 (Igf1), glu-cose-6-phosphate isomerase（Gpi）, GABA type A receptor-associated protein-like 1(Gabarapl1), and Thyroid hormone receptor beta (Thrb) showed the most expression difference, and then were selected to verification by qRT-PCR. The result of qRT-PCR was consistent with that of transcriptome sequencing. Conclusion This study provided information of molecular mechanisms underlying the developmental differences in skeletal muscles between specialized duck lines.