Characterization of a Novel Porcine CSN2 Polymorphism and Its Distribution in Five European Breeds

Abstract

Here, we describe a novel porcine β-casein (CNS2) polymorphism, initially identified using the isoelectric focusing (IEF) technique, and provide its distribution in five European breeds. Porcine CSN2 cDNA samples, from sows identified using IEF as carriers of polymorphic variants, were sequenced, and based on the sequence alignments, a genotyping assay was developed. The distribution of the polymorphism was investigated by genotyping 167 sows. Population genetic indexes were computed using POPGENE32 version 1.32. Sequence alignments revealed that the mutation which caused the different β-casein IEF migration profiles was c.647G>A, a substitution located in exon 7, which modifies the amino acid from position 201 of the mature protein from arginine to glutamine. The frequency of the G allele was 0.965 in the investigated Landrace population (number of individuals genotyped n = 67), one in the Pietrain population (n = 40), 0.705 in the Large White population (n = 36), 0.885 in the Bazna population (n = 13), and 0.555 in the Mangalita population (n = 11). For all breeds, except Pietrain (monomorphic), the genotype distribution was in accordance with the Hardy-Weinberg equilibrium. Given that β-casein is the most important protein in sows' milk, a polymorphism like the one described here may prove interesting for marker-assisted selection.

Keywords: CSN2; Sus scrofa; pig; polymorphism.

Figure 1

Porcine CSN2 c.647G>A polymorphism: (A) The isoelectric focusing (IEF) migrating profiles of the two polymorphic protein variants (lane 1—AG; lane 2—AA; lane 3—GG); (B) CSN2 cDNA sequencing chromatograms from 3 individuals carrying different genetic variants of the gene—the mutational event is marked with a square.

Figure 2

Agarose gel electrophoretic profiles belonging to the 3 porcine CSN2 c.647G>A genotypes, following the restriction of amplification products with the StyI endonuclease. Lane 1—unrestricted product; lane 2—AmpliSize Molecular Ruler 50–2000 bp Ladder (BioRad); lane 3—AG; lane 4—GG; lane 5AA.