Gene expression of myosin heavy chain isoforms (MyHC) with different growth traits in Nellore cattle

The molecular structure of myosin heavy chain isoforms (MyHC) would be responsible for the properties of species-specific rigor mortis. The specific relationship between muscle fibre type and animal growth is still highly controversial. The aim of this study was to evaluate the gene expression of myosin heavy chain isoforms (MyHC) with different growth traits in Nellore cattle. Ninety Nellore animals were used. The animals were pasture-fed until approximately 24 months of age, when they were moved to feedlot. The feedlot period was 95 days with average body weight of approximately 550 kg. The animals were weighed at the beginning of the feedlot period and every 28 days until slaughter. Immediately after slaughters, samples for gene expression analysis were collected. Two extreme groups, one group contained small animals and other large animals (n = 24 animals / group) were separated, according to the weight gain (WG) and slaughter weight (SW). Total RNA was extracted from skeletal muscle samples and was used for quantitative real-time PCR (qRT-PCR) reactions by Taqman probes. As reference genes were used the glyceraldehydes 3-phosphate dehydrogenase (GAPDH), TATA box binding protein (TBP) and Beta Actin (ACTB) and as target genes of MyHC isoforms were used MYH7, MYH2 and MYH1. The statistical linear mixed models for the qRT-PCR data were used, as proposed by literature. The animal group named as small presented SW and WG average of 504.58 ? 32.36 and 130.50 ? 32.99 kg, respectively. The group of large animals presented SW and WG average of 604.83 ? 42.98 and 186.58 ? 30.96 kg, respectively. Expression of MYH7 and MYH2 genes did not differ significantly (P> 0.05) between the two groups. The relative expression of the MYH1 gene was 3.38 times higher in small animals compared to the large animals group. Nellore cattle with different growth traits have different gene expression patterns of MYHC1.