Polymorphism of insulin-like growth factor 1 gene and its association with litter size in Small Tail Han sheep

The insulin-like growth factor 1 (IGF1) gene was studied as a candidate gene for high prolificacy in sheep. Polymorphisms of 5' regulatory region and all four exons of IGF1 gene were detected in Small Tail Han (n = 277), Hu (n = 58), Texel (n = 48) and Dorset (n = 46) sheep by PCR-RFLP and PCR-SSCP analysis. A microsatellite polymorphic site and a restriction fragment length polymorphism were shown in the 5' regulatory region of IGF1 gene. The ewes with genotype 123/123 bp had 0.81 (P < 0.05) or 1.03 (P < 0.01) lambs more than those with genotype 125/125 bp or 125/127 bp, the ewes with genotype 123/125 bp had 0.46 (P < 0.05) or 0.68 (P < 0.01) lambs more than those with genotype 125/125 bp or 125/127 bp. In addition, there were two mutations (C1511G and A1513G) in 5' regulatory region of IGF1 gene. The ewes with genotype BB or AB had 0.96 (P < 0.05) or 0.38 (P < 0.05) lambs more than those with genotype AA, but there were no significant differences between BB and AB genotypes (P > 0.05) in Small Tail Han sheep. These results preliminarily indicated that these polymorphisms of IGF1 gene could be used in molecular marker-assisted selection for sheep breeding programs.