Short Communication: The β-Casein (CSN2) Silent Allele C1 Is Highly Spread in Goat Breeds

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 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.

Genetic Characterisation ofCSN2Gene inGirgentanaGoat Breed

“…At least, ten alleles have been identified in goat CSN2 gene. In particular, seven of these alleles (A, A1, C, C1, E, 0, and 0') were characterised at DNA level (Rando et al, 1996;Persuy et al, 1999;Chessa et al, 2005Chessa et al, , 2008Cosenza et al, 2005), whereas B and D alleles were described only at protein level (Mahé and Grosclaude, 1993;Galliano et al, 2004). Another variant has been found by Chianese et al (2007) at protein level but it was not yet characterised.…”

“…The first protocol was used to amplify a 374 bp fragment of exon 7 using primers and PCR conditions by Chessa et al (2005) in order to discriminate A/A1, C/C1, E, and 0' alleles. The second protocol was used to discriminate allele C to C1 amplifying a 325 bp fragment of exon 9 using primers by Chessa et al (2008) and PCR conditions by Chessa et al (2005) with an annealing temperature of 56°C. Finally, the polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) protocol proposed by Cosenza et al (2005) was used to discriminate allele A to A1.…”

Quantitative determination of casein genetic variants in goat milk: Application in Girgentana dairy goat breed

“…The data obtained for b-casein showed a lower content of this protein associated to C and C1 alleles (3.0 ± 0.8 and 2.0 ± 0.7 g/L, respectively) compared with those published by Chessa, Rignanese, Küpper, et al (2008), that report the CSN2 A, A1, B, C, C1, D, E alleles associated with higher content (5.0 g/L/allele). The application of our analytical method allowed the separation of A and B alleles at j-casein (Table 1), with the first associated with higher protein content than the second one (1.6 ± 0.3 and 1.1 ± 0.2).…”

“…The allele A at this locus was assigned when all the other alleles were not present. The CSN2 A/A1, C, C1, E, and 0' alleles were identified using PCR protocols of Chessa et al (2005) and Chessa, Rignanese, Küpper, et al (2008), amplifying part of exon 7-intron 8, and exon 8-intron 9, followed by sequencing of amplified fragments with ABI PRISM 3130xl Genetic Analyzer (Applied Biosystems). Moreover, PCR-RFLP protocol proposed by Cosenza, Paciullo, Gallo, Di Berardinno, and Ramunno (2005) was used to discriminate allele A to A1.…”

“…The b-casein (encoded by CSN2 gene) presents alleles associated with a normal content (5.0 g/L/allele) and null alleles associated with the absence of this casein fraction in milk (Chessa, Rignanese, Küpper, et al, 2008).…”