Molecular characterization and genetic variability at κ-casein gene (CSN3) in camels

κ-casein is a glycosilated protein belonging to a family of phosphoproteins (αs1, β, αs2, κ) that represent the major protein component in mammalian milk. κ-casein plays an essential role in the casein micelle stabilization, determining the size and the specific function. In the present paper, we report for the first time the characterization of the nucleotide sequence of the whole κ-casein-encoding gene (CSN3) plus 1045 nucleotides at the 5′ flanking region in Camelus dromedarius. The promoter region and the complete cDNA were also provided for the first time in Camelus bactrianus. The gene is spread over 9.3 kb and consists of 5 exons varying in length from 33 bp (exon 3) to 494 bp (exon 4), and 4 introns from 1200 bp (intron 3) to 2928 bp (intron 2). Highly conserved sequences, located in the 5′ flanking region, have been found. The regulatory regions of camels seems to be more related to equids than to other compared species. 17 polymorphic sites have been detected, one of these (g.1029T>C) is responsible for the creation of a new putative consensus sequence for the transcription factor HNF-1. In general, these SNPs are the first reported in camels for casein loci. Finally, seven interspersed repeated elements were also identified at intronic level.

► The camel κ-casein gene (CSN3) and its promoter region was sequenced and characterized.
► The regulatory regions of camels seems to be more related to equids than to ruminants.
► 7 interspersed elements have been found.
► One LINE is distinctive of the camel CSN3 gene.
► The SNP g.1029T>C creates a putative binding site for the transcription factor HNF-1.