Identification of Differentially Expressed Transcripts in M. 'Longissmus Dorsi' With Divergent Marbling Phenotypes in Hanwoo (Korean Native Cattle)

Marbling is a major trait in determining profit in the Korean beef industry. However, the underlying biology of muscles with divergent marbling phenotypes is still poorly understood in cattle. In this study, we attempted to detect differentially expressed genes in M. longissimus dorsi in Hanwoo steers with high and low estimated breeding values for marbling score using an Affymetrix bovine gene expression array. Three data-processing methods (MAS5.0, GCRMA and RMA) were implemented to test for differential expression (DE). Analysis identified 21 transcripts exhibiting significant DE in at least two data-processing methods (P<0.001). Squalene epoxidase and Cytochrome P450 gene, thought to play a role in biotransformation of steroids, were expressed more in highly marbled muscle whereas gene for Arginyl-tRNA synthetase, Ribosomal protein S6 kinase, Thimetoligopeptidase 1, Proteosome activator subunit 4, ATP binding protein and CDC-like kinase gene, which are all involved in protein synthesis and cell division, were down-regulated in highly marbled muscle. These results suggest that down-regulation of genes involved in cell division, growth regulation and protein synthesis may lead to decreased muscle mass and increased adiposity within muscle.