Candidate gene approaches provide tools for exploring and localizing causative genes affecting quantitative traits and the underlying variation may be better understood by determining the relative magnitudes of effects of their polymorphisms. Diacyglycerol O-acyltransferase 1 (DGAT1), fatty acid binding protein (heart) 3 (FABP3), growth hormone 1 (GH1), leptin (LEP) and thyroglobulin (TG) have been previously identified as genes contributing to genetic control of subcutaneous fat thickness (SFT) in beef cattle. In the present research, Bayesian model selection was used to evaluate effects of these five candidate genes by comparing competing non-nested models and treating candidate gene effects as either random or fixed. The analyses were implemented in SAS to simplify the programming and computation. Phenotypic data were gathered from a F2 population of Wagyu × Limousin cattle. The five candidate genes had significant but varied effects on SFT in this population. Bayesian model selection identified the DGAT1 model as the one with the greatest model probability, whether candidate gene effects were considered random or fixed, and DGAT1 had the greatest additive effect on SFT. The SAS codes developed in the study are freely available and can be downloaded at: http://www.ansci.wsu.edu/programs/.

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Evaluation of candidate gene effects for beef backfat via Bayesian model selection.

The contribution of five candidate genes to the variation in meat tenderness, pH, colour, marbling and water holding capacity (WHC) was analysed in muscle samples from 243 young bulls of Angus, Charolais, Hereford, Limousin, or Simmental breed, raised in Swedish commercial herds The animals were genotyped for single nucleotide polymorphisms (SNPs) in the genes encoding calpain 1 (CAPN1:c947G>C), calpastatin, (CAST:c155C>T), diacylglycerol O-acyltransferase 1 (DGAT1), leptin (UASMS2C>T) and stearoyl-CoA desaturase 1 (SCD1) 
	
The CAPN1:c947G>C SNP showed associations with marbling and meat colour, and to some extent also tenderness The CAST:c155C>T T allele, which was the most common allele, showed a favourable association with Warner Bratzler shear force (WBSF) and compression tests The K232A polymorphism at the DGAT1 gene was associated with level of beef marbling An association was observed between UASMS2C>T and compression tests and meat colour The SCD1 SNP was associated with variation in meat colour traits after 6 days with access to oxygen There was no association of the tested SNPs with WHC traits and pH value 

	Our results show that gene effects are of importance for quality of meat from Swedish young bull of beef breed and Swedish beef can therefore be improved by including beef quality and DNA-tests in the breeding program The CAST:c155C>T SNP proved to be a good marker for tenderness in Swedish beef

/pdf/candidate-gene-effects-on-beef-quality-17qrnxhsx0.pdf

Candidate gene effects on beef quality

Triacylglycerols are quantitatively the most important storage form of energy for eukaryotic cells. Acyl CoA:diacylglycerol acyltransferase (DGAT, EC 2.3.1.20) cat- alyzes the terminal and only committed step in triacylglycerol synthesis, by using diacylglycerol and fatty acyl CoA as substrates. DGAT plays a fundamental role in the metabolism of cellular diacylglycerol and is important in higher eu- karyotes for physiologic processes involving triacylglycerol metabolism such as intestinal fat absorption, lipoprotein assembly, adipose tissue formation, and lactation. DGAT is an integral membrane protein that has never been purified to homogeneity, nor has its gene been cloned. We identified an expressed sequence tag clone that shared regions of similarity with acyl CoA:cholesterol acyltransferase, an enzyme that also uses fatty acyl CoA as a substrate. Expression of a mouse cDNA for this expressed sequence tag in insect cells resulted in high levels of DGAT activity in cell membranes. No other acyltransferase activity was detected when a variety of sub- strates, including cholesterol, were used as acyl acceptors. The gene was expressed in all tissues examined; during differen- tiation of NIH 3T3-L1 cells into adipocytes, its expression increased markedly in parallel with increases in DGAT activ- ity. The identification of this cDNA encoding a DGAT will greatly facilitate studies of cellular glycerolipid metabolism and its regulation.

Identification of a gene encoding an acyl CoA:diacylglycerol acyltransferase, a key enzyme in triacylglycerol synthesis (fatty acidycloningyexpressed sequence tagyglycerolipid)

C Olin Collins

Papers

Identification of a gene encoding an acyl CoA:diacylglycerol acyltransferase, a key enzyme in triacylglycerol synthesis (fatty acidycloningyexpressed sequence tagyglycerolipid)