Genetic polymorphisms within coding region of insulin like growth factor-1 gene in six indigenous draught cattle

Abstract

The study was undertaken to detect genetic polymorphisms in the coding regions of bovine insulin-like growth factor (IGF-1)  gene  in  six  indigenous  draught  cattle  breeds  viz.,  Bargur,  Hallikar,  Kangayam,  Ongole,  Pullikulum  and Umblachery. A total of 312 blood samples (52 samples from each breed) were collected and genomic DNA was isolated. Four sets of primers were designed for the expressed regions of the IGF-1 gene. The presence of six single nucleotide polymorphisms (SNPs) was detected after sequencing and analysis. The sizes of amplicons (607, 454, 518 and 671 bp) obtained covered the exons one to four with intronic sequences on either sides. The SNPs in exon 1 were at positions g. 213G>A (transition) and g. 244C>A (transversion) between Bos taurus and Bos indicus cattle. The variation at  first position  resulted  in  non-synonymous  mutation,  replacing  the  amino  acid  ‘Serine’  with  Asparagine’.  Whereas the mutation at position g. 244C>A, resulted in a stop codon (TGA). At position g. 4827 in exon 2, a ‘G’ to ‘A’ transition was observed, which resulted in synonymous mutation. In exon 3, three SNPs were observed at positions g. 56233G>A (transition), g. 56317G>T (transversion) and g. 56354A>T (transversion).  These variations resulted in non-synonymous changes in amino acid sequences, i.e. from ‘Arginine’ to ‘Lysine’, ‘Lysine’ to ‘Asparagine’ and ‘Methionine’ to ‘Leucine’ respectively.  This  region  exhibited  maximum  polymorphisms  at  different  loci  whereas;  the  fourth  exon exhibited the greatest homology between Bos taurus and Bos indicus cattle, showing no variation in any of the positions. Genotyping these SNPs in larger number will give significant information on the role of these SNPs among Indian draught cattle.