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Gene expression patterns during intramuscular fat development in cattle

YongHong Wang^*,#, Antonio Reverter^*,#, Siok Hwee Tan^*,#, Nadia De Jager^*,,#, Ran Wang^*,#, Sean M. McWilliam^*,#, Linda M. Cafe^,#, Paul L. Greenwood^,# and Sigrid A. Lehnert^*,#

^* CSIRO Livestock Industries, Queensland Bioscience Precinct, 306 Carmody Rd, St. Lucia, Queensland 4067, Australia , School of Biological & Chemical Sciences, University of Queensland, Qld 4072, Australia , Beef Industry Centre of Excellence, NSW Department of Primary Industries, JSF Barker Building, University of New England, Armidale, New South Wales 2351, Australia ^# Cooperative Research Centre for Cattle and Beef Quality

yonghong.wang{at}csiro.au

Abstract

Deposition of i.m. fat or marbling in beef cattle contributes significantly to meat quality parameters, including juiciness, flavor and tenderness. The accumulation of i.m. fat is largely influenced by the genetic background of cattle, as well as their age and nutrition. To identify genes that can be used as early biomarkers for the prediction of marbling capacity; we studied the muscle transcriptome of 2 cattle crossbreeds with contrasting i.m. fat content. The transcriptomes of marbling LM tissue of heifers from Wagyu x Hereford (WxH; n = 6) and Piedmontese x Hereford (PxH; n = 7) crosses, were profiled using a combination of cDNA microarray and quantitative reverse transcription PCR (qRT-PCR). Five biopsies of LM were taken from each animal at approximately 3, 7, 12, 20 and 25 mo from birth. Tissue was also collected from the LM of each animal at slaughter (~ 30 mo). Microarray experiments, conducted on the first three biopsies of two animals from each crossbreed, identified 97 differentially expressed (DE) genes. The gene expression results indicated that the LM transcriptome of animals with high marbling potential (WxH) can be reliably distinguished from less marbled animals (PxH) when the animals are as young as 7 mo of age. At this early age one can not reliably determine meaningful differences in i.m. fat deposition. We observed greater expression of a set of adipogenesis and lipogenesis-related genes in the LM of young WxH animals compared with their PxH contemporaries. In contrast, genes highly expressed in PxH animals are associated with mitochondrial oxidative activity. Further qRT-PCR experiments revealed that the mRNA of 6 of the lipogenesis-related genes also peaked at the age of 20 to 25 mo in WxH animals. The mRNA levels of ADIPOQ, SCD, and THRSP are highly correlated with i.m. fat content of an individual in WxH animals. Our study provides clear evidence of early molecular changes associated with marbling and also identifies specific time frames when i.m. fat development in cattle muscle can be detected using gene expression. This information could be used by animal scientists to design optimal nutrition for high marbling potential. In addition, the genes found to be highly expressed during development of marbling could be used to develop genetic markers or biomarkers to assist with beef production strategies.

Key Words: cattle • gene expression • intramuscular fat • marbling • microarray • muscle