Biochemical characteristics and key regulatory genes of intramuscular fat deposition in aged Nanchuan chickens

Intramuscular fat (IMF) is an important indicator affecting chicken quality. However, there are few studies on IMF in aged chickens. Nanchuan chicken is an excellent local egg and meat dual-purpose breed in Southwest China, renowned for its delicious flavor and fresh meat. In this study, biochemical characteristics and regulation mechanism of IMF deposition in aged Nanchuan chickens were systematically clarified. Slaughter performance, the IMF, triglyceride (TG), phospholipid (PLIP), total cholesterol (TCHO) and Fatty acids (FA) content in the breast muscle of 55-week-old Nanchuan chicken was measured, and RNA sequencing was integrated to explore the regulatory genes of IMF deposition. The results showed that the IMF content and whole net carcass yield in the high IMF group were significantly higher than those in the low IMF group (P < 0.01), while the shear force showed the opposite pattern. And, TG content in the high IMF group was significantly higher than that of the low IMF group (P < 0.05), and it was significantly positively correlated with the IMF content (P < 0.01). Meanwhile, we detected four FAs (C20:1n10, C20:4n6, C22:5n6, C22:6n3) in the high IMF group were significantly higher than those in the low IMF group (P < 0.05). In addition, the RNA sequencing results showed 469 up-regulated differentially expressed genes (DEGs) were identified, and these up-regulated DEGs were significantly enriched in ECM-receptor interaction, actin cytoskeleton regulation and focal adhesion pathways (P < 0.05). Among these DEGs, THBS1, THBS2, ITGA2, ITGA9, ITGAV and LUM were confirmed to be related to IMF deposition by protein-protein interaction (PPI) network, correlation analysis and gene expression level analysis, and these genes were hardly reported in researches of chicken IMF deposition. Our findings will help fully elucidate the mechanism of IMF formation of chickens and provide a theoretical foundation for the protection and utilization and the genetic improvement of Nanchuan chicken. Keywords: Aged Nanchuan chicken; Intramuscular fat; RNA sequencing; Regulatory gene.