[Genetic polymorphisms and genetic effects of IGF2 gene in pigs].
ABSTRACT Single nucleotide polymorphisms of the exon7, 8, 9 of the porcine IGF2 gene were tested using PCR-SSCP. Genetic effects of the IGF2 gene on birth weight, weaning weight, six-month weight and six-month backfat thickness were analyzed. On the basis of the published DNA sequence (AY044828) of the porcine IGF2 gene, three pairs of primers were designed, and one polymorphism, three genotypes were found in the PCR product amplified with Ex8 primers. C-->T transition at 53 site of exon8 was detected by sequencing the homozygotes. The results showed that: firstly, the genotype distribution was not consistent among the different pig breeds. No significant differences (P > 0.05) were found in the genotype distribution when compared the Landrace with the Large White , the Laiwu with the Dapuliang, and the Yimeng with the Licha Black pig breeds, whereas significant differences (P lt; 0.01) were found among other tested pig breeds in the genotype distribution. Secondly, on the basis of the fixed effect model, significant differences (P lt; 0.05) were found in birth weight and six-month backfat thickness, whereas no significant differences (P > 0.05) existed in weaning weight and six-month weight. Thirdly, using least square analysis, it was shown that individuals of the BB genotype have significantly lower (P lt; 0.05) birth weight than those of AA and AB genotypes, with the order being AB > AA > BB ; Individuals of the AA genotype have significantly lower (P lt; 0.05) six-month backfat thickness than those of AB and BB genotypes, with the order being BB > AB > AA. These results suggest that IGF2 gene has significant effects on individual birth weight and backfat thickness. The IGF2 gene can be used in marker-assisted selection to accelerate the breeding progress.
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ABSTRACT: IGF2 is the major candidate gene for a paternally expressed Quantitative Trait Locus (QTL) in the pig primarily affecting muscle development. Here we report two sequence contigs together comprising almost 90 kb containing the INS-IGF2 and H19 genes. A comparative sequence analysis of the pig, human, and mouse genomic sequences was conducted to identify the exon/intron organization, all promoters, and other evolutionarily conserved elements. RT-PCR analysis showed that IGF2 transcripts originated from four different promoters and included various combinations of seven untranslated exons together with three coding exons, in agreement with previous findings in other mammals. The observed sequence similarity in intronic and intragenic regions among the three species is remarkable and is most likely explained by the complicated regulation of imprinting and expression of these genes. The general trend was, as expected, a higher sequence similarity between human and pig than between these species and the mouse, but a few exceptions to this rule were noted. This genomic region exhibits several striking features, including a very high GC content, many CpG islands, and a low amount of interspersed repeats. The high GC and CpG content were more pronounced in the pig than in the two other species. The results will facilitate the further characterization of this important QTL in the pig.Mammalian Genome 08/2002; 13(7):388-98. · 2.42 Impact Factor
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ABSTRACT: Most traits and disorders have a multifactorial background indicating that they are controlled by environmental factors as well as an unknown number of quantitative trait loci (QTLs). The identification of mutations underlying QTLs is a challenge because each locus explains only a fraction of the phenotypic variation. A paternally expressed QTL affecting muscle growth, fat deposition and size of the heart in pigs maps to the IGF2 (insulin-like growth factor 2) region. Here we show that this QTL is caused by a nucleotide substitution in intron 3 of IGF2. The mutation occurs in an evolutionarily conserved CpG island that is hypomethylated in skeletal muscle. The mutation abrogates in vitro interaction with a nuclear factor, probably a repressor, and pigs inheriting the mutation from their sire have a threefold increase in IGF2 messenger RNA expression in postnatal muscle. Our study establishes a causal relationship between a single-base-pair substitution in a non-coding region and a QTL effect. The result supports the long-held view that regulatory mutations are important for controlling phenotypic variation.Nature 11/2003; 425(6960):832-6. · 38.60 Impact Factor
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ABSTRACT: IGF2-in3-G3072A is a causative mutation for paternally expressed quantitative trait loci on the p arm of porcine chromosome 2 with substantial effect on muscle growth and backfat thickness. The linkage disequilibrium between IGF2-in3-G3072A and IGF2-in7-G162C (IGF2-NciI) in four breeds and associations between these polymorphisms and growth and meat performance in pigs of the Large White breed were analysed. A significant effect of these polymorphisms on backfat thickness and lean meat content was found. In addition, we identified two new single nucleotide polymorphisms (SNPs) in intron 7 of the gene. The existence of complete linkage disequilibrium between IGF2-in3-G3072A locus in the population under study where the locus segregated and SNPs in intron 7 of the IGF2 gene detectable with simple and reliable polymerase chain reaction-restriction fragment length polymorphism techniques (G162C, C179G and G186T) offer possibilities to use these SNPs for genotyping of quantitative trait nucleotide in Large White and Landrace breeds.Journal of Animal Breeding and Genetics 07/2006; 123(3):204-7. · 1.65 Impact Factor