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Promoter region of the bovine growth hormone receptor gene: single nucleotide polymorphism discovery in cattle and association with performance in Brangus bulls

A. J. Garrett^*, G. Rincon, J. F. Medrano, M. A. Elzo^#, G. A. Silver^* and M. G. Thomas^*

^* New Mexico State University, Las Cruces, NM 88003 , University of California, Davis, CA 95616 ^# University of Florida, Gainesville, FL 32611

milthoma{at}nmsu.edu

Abstract

Expression of the GH receptor (GHR) gene and its binding with GH is essential for growth and fat metabolism. A GT-microsatellite exists in the promoter of bovine GHR segregating short (11 bp) and long (16 to 20 bp) allele sequences. To detect SNP and complete an association study of genotype to phenotype, we resequenced a 1,195 bp fragment of DNA including the GT microsatellite and Exon 1A. Resequencing was completed in 48 familialy unrelated Holstein, Jersey, Brown Swiss, Simmental, Angus, Brahman, and Brangus cattle. Nine SNP were identified. Phylogeny analyses revealed minor distance (i.e., < 5%) in DNA sequence among the 5 Bos taurus breeds; however, sequence from Brahman cattle averaged 27.4 ± 0.07% divergence from the Bos taurus breeds, whereas divergence of Brangus was intermediate. An association study of genotype to phenotype was completed with data from growing Brangus bulls (n = 553 from 96 sires) and data from 4 of the SNP flanking the GT-microsatellite. These SNP were found to be in Hardy-Weinberg equilibrium and in phase based on linkage disequilibrium analyses (r² = 0.84 and D’= 0.92). An A/G tag SNP was identified (ss86273136) and was located in Exon 1A, which started 88 bp downstream from the GT microsatellite. Minor allele frequency of the tag SNP was greater than 10% and Mendelian segregation was verified in 3 generation pedigrees. The A allele was derived from Brahman and the G allele was derived from Angus. This tag SNP genotype was a significant effect in analyses of rib fat data collected with ultrasound when bulls were ~365 d of age. Specifically, bulls of the GG genotype had 6.1% more (P = 0.0204) rib fat than bulls of the AA and AG genotypes, respectively. Tag SNP (ss86273136), located in the promoter of GHR, appears to be associated with a measure of corporal fat in Bos taurus x Bos indicus composite cattle.

Key Words: bovine • Brangus • DNA • growth hormone receptor • SNP