Molecular evolution of coding and non-coding sequences of the growth hormone receptor (GHR) gene in the family Bovidae

Abstract

The GHR gene exon 1A and exon 4 with fragments of its flanking introns were sequenced in twelve Bovidae species and the obtained sequences were aligned and analysed by the ClustalW method. In coding exon 4 only three interspecies differences were found, one of which had an effect on the amino-acid sequence--leucine 152 proline. The average mutation frequency in non-coding exon 1A was 10.5 per 100 bp, and was 4.6-fold higher than that in coding exon 4 (2.3 per 100 bp). The mutation frequency in intron sequences was similar to that in non-coding exon 1A (8.9 vs 10.5/100 bp). For non-coding exon 1A, the mutation levels were lower within than between the subfamilies Bovinae and Caprinae. Exon 4 was 100% identical within the genera Ovis, Capra, Bison, and Bos and 97.7% identical for Ovis moschatus, Ammotragus lervia and Bovinae species. The identity level of non-coding exon 1A of the GHR gene was 93.8% between species belonging to Bovinae and Caprinae. The average mutation rate was 0.2222/100 bp/MY and 0.0513/100 bp/MY for the Bovidae GHR gene exons 1A and 4, respectively. Thus, the GHR gene is well conserved in the Bovidae family. Also, in this study some novel intraspecies polymorphisms were found for cattle and sheep.