Several single nucleotide polymorphisms have been identified in the goat milk casein genes, most of them modifying the amino acid sequence of the coded pro- tein. At least 9 variants have been found in goat β-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 al- leles 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.
Short communication: The β-casein (CSN2) silent allele C1 is highly spread in goat breeds
Chessa S.;
2008-01-01
Abstract
Several single nucleotide polymorphisms have been identified in the goat milk casein genes, most of them modifying the amino acid sequence of the coded pro- tein. At least 9 variants have been found in goat β-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 al- leles 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.
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