Molecular cloning, SNP detection and association analysis of 5' flanking region of the goat IGF1 gene with prolificacy.

The insulin-like growth factor 1 has an important role in reproduction, foetal development and growth. It regulates the secretion of gonadotrophin releasing hormone, stimulates ovarian function and steroidogenesis. The present study was conducted to characterise the 5' flanking region of goat IGF 1 gene, ascertain ovarian expression of the IGF1 gene, detect SNPs and assess the association with prolificacy in the two indigenous goat breeds of South India viz., low prolific Attappady Black and high prolific Malabari. The 5' flanking region of IGF1 gene was PCR amplified, cloned and sequenced from both breeds. Genotyping was performed in 277 goats from the two genetic groups using the PCR-Single Strand Conformational Polymorphism (SSCP) and the expression of the IGF1 gene in the ovary was analysed by quantitative real time PCR. The 5' flanking region of the IGF1 gene was 601 bp long and located at 450 bp upstream of the start codon. Sequence exhibited 97-99% similarity with that of the sheep, cattle and sika deer IGF1 genes. Three genotypes, PP, PQ and QR were observed at this locus with the frequency of 0.62, 0.30 and 0.08, respectively. Sequencing of the representative PCR products from each genotype revealed two SNPs, g.224A>G and g.227C>T. The population was found to be in Hardy-Weinberg disequilibrium at both loci. Statistical results indicated that these loci were associated with litter size (P ≤ 0.05). However, no significant difference was found in the expression of the IGF1 gene in the ovaries of the two goat breeds. These results suggest the significant influence of the IGF1 gene on prolificacy in goats and identified SNPs would benefit the selection of prolific animals in future breeding programs.