PSVII-22 Age-related transcriptome changes associated with beef quality in longissimus thoracis muscle of Hanwoo steer

Abstract Understanding age-associated transcriptome changes in longissimus thoracis (LT) muscle is important for determining beef quality and yield characteristics. We investigated age-related transcriptome changes in LT of Hanwoo (Korean cattle) steers. Hanwoo steers [n = 11; initial body weight (BW) = 354 ± 5.53 kg; age, 12 ± 0.28 mo] were used. The LT samples were biopsied between the 11th and 12th ribs at 12, 18, and 24 mo of age. Steers were slaughtered at 31 mo of age (789 ± 17.7 kg) and LT samples were collected. For transcriptome analysis, six LT samples from steers at each of the four ages were selected based on initial BW, carcass weight, rib eye area, carcass quantity, and beef quality grades. Transcriptomic profiles at various ages were measured by RNA sequencing (RNA-seq). A total of 13,753 transcriptomes were identified, and a total of 2,522 differentially expressed genes (DEGs: 743 up-regulated and 1088 down-regulated genes) between 12 mo and 31 mo of age were identified (false discovery rate < 0.05 and |fold change| ≥ 2). Gene ontology annotation analysis of these DEGs showed several significant (P < 0.05) terms including blood vessel morphogenesis, external encapsulating structure, and cell adhesion molecule binding. Pathway analysis of these DEGs revealed several significant (P < 0.05) Kyoto encyclopedia of genes and genomes (KEGG) pathways including pathways in cancer, MAPK signaling pathway, and cell adhesion molecules. Transcriptomic expression patterns of the up-regulated and the down-regulated genes of the significant functional annotation terms between 12 mo and 31 mo were validated using all animals by quantitative real-time polymerase chain reaction analysis. Protein expression patterns of nuclear receptor subfamily 4 group A member 1, coagulation factor II thrombin receptor, and growth arrest and DNA damage inducible alpha genes were validated by Western analyses. In conclusion, age-related gene expression changes suggest that pathways involved in the regulation of vascular morphogenesis and cell adhesion molecules provide novel insights into understanding the molecular mechanisms responsible for beef quality and carcass weight in beef cattle.