Novel polymorphisms of the IGF1R gene and their association with average daily gain in Egyptian buffalo (Bubalus bubalis)

Abstract

The objective of this study was to detect insulin-like growth factor 1 receptor (IGF1R) polymorphisms, their allele, and genotype frequencies and to determine associations between these polymorphisms and growth traits in Egyptian water buffalo. Three loci of the IGF1R coding region were amplified by RT-PCR and, subsequently, subjected to sequence analysis, followed by single-strand conformation polymorphism to identify different allelic patterns. A total of 11 novel polymorphisms were detected; 6 SNPs among Egyptian water buffaloes and 5 polymorphisms compared with Indian buffalo (Y12700). Three of those polymorphisms; GAG Indel polymorphism, C261G, and G263C SNPs, were nonsynonymous mutations. The GAG Indel polymorphism led to deletion of E (glutamic) amino acid (aa) in the IGF1R of Egyptian water buffaloes compared with Indian buffalo. However, C261G SNP, which replaced A (alanine) by G (glycine) aa, and G263C SNP, which changed A (alanine) to P (proline) aa, were detected among Egyptian water buffaloes. Three different single-strand conformation polymorphism patterns were observed in exon 21: CC/CC, GG/GG, and CG/GC with frequencies of 0.291, 0.253, and 0.556, respectively. The heterozygous animals (CG/GC) had a higher ADG than homozygous animals (CC/CC and GG/GG) from birth to 6 mo of age. We conclude that the heterozygous haplotype, C261G/G263C, in exon 21 of the IGF1R gene is associated with the ADG during the early stages of life (from birth to 6 mo of age) and could be used as a genetic marker for selection of growth traits in Egyptian buffalo.

Keywords: Average daily gain; Egyptian buffalo; IGFIR gene; SNPs; SSCP; Sequencing.