A preliminary analysis of mRNA transcribed from the N allele at the CSN1S1 locus of the goat

Abstract

The goat αS1-casein is a main milk phosphoprotein of 199 aminoacid residues long. The αS1-casein gene (CSN1S1) contains 19 exons, ranging in size from 24 to 385 bp (for a total of 1138 bp) in the coding region, spread over about 17,5 kb transcription unit (Leroux et al., 1992). The goat αS1-casein exhibits both qualitative and quantitative remarkable variation arising from genetic polymorphism in the encoding gene. In particular, two alleles, CSN1S1 01 and 02, associated with a null content of the corrisponding protein, were detected (Martin et al., 1999), characterized by large DNA deletion (Cosenza et al., 2002) and insertion (Martin et al., 1999) events, respectively. Recently, by means of SDS-PAGE and CSN1S1 gene sequence analysis of goat individual milk and DNA sample, another allele (CSN1S1 N), associated with an apparently null amount of this protein fraction in the milk, was identified (Ramunno et al., 2002). This allele is characterized by the citosine deletion at position 23 in the 98th exon of the gene, likewise to CSN1S1 F allele (associated to a low content of αS1- casein) and, contrary to this one, for the absence of two insertions, 11 and 3 bp base pair in length, in the downstream intron. The present work reports the results of a preliminary analysis of mRNA transcribed from the N allele at goat CSN1S1 locus compared with the one transcribed from a homozygote individual for the CSN1S1 A allele.