Polymorphism of IGF-I and ADRB3 Genes and Their Association with Growth Traits in the Iranian Baluchi Sheep

Abstract

Baluchi sheep is considered as the most common breed in Iran, constituting about 30% of total sheep population, approximately 15 million heads. This research was designed to study the incidence of mutation in two loci of IGF-I (Exon 3) and ADRB3 (Intron) along with their association with body weight traits in Baluchi sheep population. Following DNA extraction from 190 Baluchi sheep, two pairs of primers were designed to amplify each gene. PCR-SSCP (Single-Strand Conformation Polymorphism) and DNA sequencing were employed to detect polymorphism of the mentioned genes. Two banding patterns were detected for IGF-I locus. The frequencies of AA, AB were recorded as 0.89, 0.11, respectively in IGF-I locus. As for ADRB3, two patterns corresponding with two genotypes (their frequencies mentioned in parentheses) of AA (0.85) and AB (0.15) were identified. One SNP change was observed in ADRB3, and one in IGF-I. A previously reported SNP was detected in exon 3 of IGF-I. The effects of IGF-I and ADRB3 polymorphism on the corrected phenotypes for body weight at birth (BW), weaning (WW), 6 months of age (6MW), 9 months of age (9MW) and 12 months of age or Yearling Weight (YW) were examined using least square methods. No significant association was detected between the polymorphism of IGF-I and body weights. As for ADRB3, the genotype AA was found out to exert a significant positive effect on 6MW (AA, 30.20±1.85 kg day-1; AB, 27.67±1.98 kg day-1; P<0.05). Keywords: Baluchi sheep, β3-Adrenergic Receptors (ADRB3), Insulin-like Growth Factor (IGF-I), PCR-SSCP, Polymorphism.