Urotensin 2 and its Receptor as Candidate Genes for Beef Marbling Score and Subcutaneous Fat Depth

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 as having: a higher relative amount of monounsaturated fatty acid (rMUFA) in beef fat phenotype as compared to the general population of bovines; a lower Δ9 desaturase activity as measured by 16:1/16:0 ratio (R2) phenotype as compared to the general population of bovines; and a smaller ribeye area (REA) phenotype as compared to the general population of bovines.
Urotensin 2 (UTS2) and its receptor (UTS2R) are associated with insulin resistant in humans, and many studies have indicated that intromyocellular lipid (IMCL) accumulation is a major contributor to insulin resistance.  In beef cattle, marbling is a subjective measurement of IMCL accumulation.  Therefore, the objective of this study was to validate the candidacy of both UTS2 and UTS2R for fat deposition in beef cattle.  Both cDNA and genomic DNA sequences of these two genes in cattle were retrieved from public databases and used to design 11 pairs of primers.  Direct sequencing of the amplicons identified 5 SNPs in UTS2 and one INDEL and 13 coding SNPs in UTS2R, respectively.  However, only one SNP in the promoter of UTS2 and the INDEL in the promote of UTS2R were chosen for genotyping on ~ 250 Wagyu x Limousin F2 population.  Statistical analysis revealed that the former gene was suggestively associated with subcutaneous fath depth (SFD) (P<0.10), but not with beef marbling score (BMS), while the latter gene was significantly associated with BMS (P<0.01), but not with SFD.  Our results provide evidence that the same orthologous gene may have conserved functions in biological or biochemical pathways, and thus explain the same or similar variations of the concordant QTLs among different species.  Therefore, cross-species candidate gene transfer is worth pursuing to facilitate understanding of genetic complexity of quantitative traits in mammals.

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Jessica McGowan
Professional Worker I
Washington State University
(509) 335-9865
Reference No: 0906-OC


Zhihua Jiang
Jennifer Michal

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