[Association of PCR-RFLP polymorphisms of IGF2 gene with fat deposit related traits in pig resource family]

Abstract

Insulin-like growth factor 2(IGF2) play an important role in fetal growth and development, tumour cell proliferation and muscle growth. IGF2 is the major candidate gene for affecting muscle mass in pig. Here we found a Nci I PCR-RFLP within intron 8 of the porcine IGF2 gene, and studied on effect of IGF2 gene on fat deposition. A fragment of 575 bp within intron 8 was obtained and digested with enzyme Nci I. PCR-RFLP analysis in a resource family of 173 pigs showed that there were two Nci I restriction loci, which are locus A and B respectively in the fragment. To locus A, single marker analysis showed that pigs with the IGF2A2A2 genotype were 9.51% for shoulder fat thickness (P < 0.01), 10.49% for 6th-7th rib fat thickness(P < 0.01), 11.46% for thorax-waist fat thickness(P < 0.05), 19.32% for buttock fat thickness (P < 0.01) and 12.59% for average backfat thickness(P < 0.01) less thick than pigs with the IGF2A1A2 genotype. Significant differences for fat percentage and lean meat percentage between the IGF2 genotypes were also seen. Individuals of homozygote of restriction alleles had a significantly higher meat color for BF than individuals of heterozygote (4.23%, P < 0.01). To locus B, single marker analysis showed the same trend as on locus A. Individuals of homozygote of restriction alleles had a significantly less average fat thickness (18.82%, P < 0.01), fat percentage (22.43%, P < 0.01) and had more lean meat percentage (8.71%, P < 0.01), meat color for BF (4.62%, P < 0.05), water moisture (0.64%, P < 0.01) than individuals of homozygote of mutation restriction allele in locus B. IGF2 gene showed mainly in the pattern of additive effect and all the dominant effect were not significant. The value of additive effect of average fat thickness, fat percentage and lean meat percentage was -0.20 +/- 0.05(P < 0.01), -2.75 +/- 0.55 (P < 0.01), 1.79 +/- 0.46(P < 0.01), respectively. Significant correlation was found between IGF2 genotype and lean meat percentage. The result suggests that the IGF2 as a candidate gene can explain significant difference for fat deposit related traits in pig.