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TFAM Gene Markers Marbling and Backfat in Beef Cattle

TFAM Gene Markers Marbling and Backfat in Beef Cattle

Significant improvements in animal performance, efficiency and carcass and meat quality have been made over the years through the application of standard animal breeding and selection techniques. However, such classical animal breeding techniques require several years of genetic evaluation of performance records on individual animals and their relatives and are therefore very expensive. Other efforts have been made to improve productivity and quality through the application of such management practices as the use of feed additives, animal hormonal implants and chemotherapeutics. However, there is significant political and regulatory resistance to the introduction and use of such methodologies. Such methodologies are also non-inheritable and need to be applied differently in every production system.
A method for identifying a bovine animal having a higher marbling score (MBS), thicker subcutaneous fat depth (SFD), or a combination thereof.
We have designed a pair of primers that amplify a product of 801 base pairs from the promoter region of mitochondrial transcription factor A (TFAM) gene in cattle.  Direct sequencing of PCR products on high and low marbling DNA pools revealed two closely-linked A/C and C/T single nucleotide polymorphisms (9 base pairs apart inclusive) in the bovine gene.  A search for transcriptional regulatory elements using MatInspector indicated that both mutations lead to a gain/loss of six putative binding sites for genes relevant to fat deposition and emergy metabolism. The A/C polymorphism can be determined with digestion of restrictive enzyme HaeIII and C/T polymorphism can be detected with digestion of restriction enzyme DpnIII, respectively.  We genotyped these two DNa markers on 237 F2 Wagyu x Limousin animals with recorded phenotypes for marbling and subcutaneous fat depth.  Marbling scores varied from 4 = Slight o to 9.5 = Moderately Abundant 50 (SD = 1.00) and fat depth measurements ranged from 0.25 to 3.30 cm (SD = 0.18).  Both SNPs were significantly associated with with marbling (P = 0.04 for A/C and P < 0.01 for C/T) and fat depth (P = 0.03 for A/C and P < 0.01 for C/T) and the five haplotypes present in the data explained approximately 7.5% and 7.0% of the variation in marbling and fat depth, respectively.  Base-pair substitution (T for C) effect at the C/T SNP was significant for both marbling and fat depth (-0.54 + 0.24 score and -0.29 + 0.11cm, respectively).  Compared with other candidate genes that may affect fat deposition (thyroglobulin, leptin, diacylglycerol O-acyltranferase, fatty acid binding protein 3 and growth hormone 1), the TFAM gene had greater effects on both marbling and backfat in this population.  If confirmed, the results may lead to a new marker for marker-assisted selection in the beef industry.
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