Variability of the IGF2 locus in the Nero Lucano pig population and its effect on quality and colourimetric characteristics of meat

According to literature data, the IGF2 (Insulin-like Growth Factor 2) gene plays a role in regulating proliferation, differentiation and apoptosis of cells in many different tissues. Furthermore, polymorphisms located in intron 3 of this gene have been associated with meat quality traits such as intramuscular fat content, marbling and backfat thickness. The aim of this study was to analyze the genetic structure of two known IGF2 SNPs (-225C>G and -182T>C), located in the promoter region P2 of IGF2 gene, in the Nero Lucano pig and their effects on quality and colourimetric characteristics of meat. Till 10 years ago, the Nero Lucano pig was a breed in danger of extinction. Today, thanks to Basilicata Regional Institutions, such as ARA, Alsia, Comunità Montana del Medio Basento, and University of Basilicata, the Nero Lucano pig population shows an increasing consistency. We typed 153 pigs at IGF2 SNPs -225C>G and -182T>C by means of RFLP-PCR analyses using Eco0109I and DraIII restriction enzymes, respectively. The frequencies of -225 C and G alleles are identical to those of -182 T and C alleles, that is 0.13 and 0.87, respectively. According to the genotype distribution it appears that only two haplotypes are present in this population: - 225G -182C, and -225C -182T. For each individual, the meat from two representative muscles (Longissimus dorsi, and Psoas) was collected. Colourimetric characteristics (CIELab lightness, L*; redness, a*; yellowness, b*; CIE, 1976), dry matter, total protein, fat content, ash (ASPA,1996) Fe heme (Hornsey 1956), oxymyoglobin (MbO2), deoxymyoglobin (deoxyMb), and metamyoglobin (metMb) content (Krzywicki 1979) where evaluated. Analysis of variance was performed on all the variables measured using the GLM procedure (SAS, 1996). The results of this study show that in Nero Lucano pig these two IGF2 haplotypes are associated with significantly different effects on chemical composition and colourimetric characteristics of meat. In particular, meat from pigs homozygous for the -225G -182C haplotype show higher values of fat, Fe heme, metMb, and lower values of protein, deoxyMb, MbO2, L* and b* parameters (P<0.05). No differences between the two haplotypes were observed for dry matter, ash and a* parameter. According to these results, the polymorphism at the IGF2 locus can be used for selection purposes in this autochtonous breed.