Short communication: the beta-casein (CSN2) silent allele C1 is highly spread in goat breeds

Several single nucleotide polymorphisms have been identified in the goat milk casein genes, most of them modifying the amino acid sequence of the coded protein. At least 9 variants have been found in goat beta-CN (CSN2); 6 of them were characterized at the DNA level (A, A1, C, E, 0, and 0'), whereas the other 3 variants were described only at the protein level. The recently identified silent A1 allele is characterized by a C-->T transition at the 180th nucleotide of the ninth exon. In the present work, typing results from different breeds (3 Italian, 3 German, and a composite of African breeds for a total of 335 samples) demonstrated that the same mutation is carried by the CSN2*C allele. In addition, the T nucleotide at the 180th nucleotide of the ninth exon was always associated with CSN2*C in all the breeds analyzed. Thus, another silent allele occurs at goat CSN2 and can be named CSN2*C1. The much wider distribution of C1 with respect to the A1 allele indicates that the single nucleotide polymorphisms characterizing the silent mutation originated from CSN2*C. A method for the identification of this allele simultaneously with 5 of the 6 DNA-characterized alleles is also proposed. The mutation involved codifies for the same protein of the C allele; nevertheless, its location in the 3' untranslated region of the gene might affect the specific casein expression.