Abstract: Marbling, defined by the amount and distribution of intramuscular fat is an economically important trait of beef cattle in Japan. Previously, researchers have found that the Myosin Heavy Chain 1 (MYH1) gene coding for an isoform of myosin heavy chain a major contractile protein which converts chemical energy into mechanical energy in muscle which is expressed in slow-twitch oxidative fiber and involved in development of the fiber and Insulin Receptor Substrate 1 (IRS1) gene encoding a signaling adaptor protein which is phosphorylated by insulin receptor and associated with insulin resistance and birth weight, possess expression differences in musculus longissimus muscle between low-marbled and high-marbled steer groups. In the present study, researchers detected Single Nucleotide Polymorphisms (SNPs), g.29850738G>A and g.120947716T>C in the promoter regions of the MYH1 and IRS1 genes, respectively between the 2 steer groups. However, the allelic distributions of the 2 SNPs were indistinguishable between Japanese Black sires with extremely high predicted breeding value for marbling and with extremely low one. An unknown SNP in the distal region upstream of ~4 kb proximal promoter regions of the MYH1 and IRS1 genes might be related to changes in gene expression and/or marbling.
Bin Tong, Seiki Sasaki, Youji Muramatsu, Takeshi Ohta, Hiroyuki Kose, Hideaki Yamashiro and Takahisa Yamada, 2012. Polymorphisms in Promoter Regions of MYH1 and IRS1 Genes Showing Marbling-Associated Expression Changes. Journal of Animal and Veterinary Advances, 11: 4441-4445.