Molecular characterization of the llamas (Lama glama) casein cluster genes transcripts (CSN1S1, CSN2, CSN1S2, CSN3) and regulatory regions

In the present paper, we report for the first time the characterization of llama (Lama glama) caseins at transcriptomic and genetic level. A total of 288 casein clones transcripts were analysed from two lactating llamas. The most represented mRNA populations were those correctly assembled (85.07%) and they encoded for mature proteins of 215, 217, 187 and 162 amino acids respectively for the CSN1S1, CSN2, CSN1S2 and CSN3 genes. The exonic subdivision evidenced a structure made of 21, 9, 17 and 6 exons for the αs1-, β-, αs2- and κ-casein genes respectively. Exon skipping and duplication events were evidenced. Two variants A and B were identified in the αs1-casein gene as result of the alternative out-splicing of the exon 18. An additional exon coding for a novel esapeptide was found to be cryptic in the κ-casein gene, whereas one extra exon was found in the αs2-casein gene by the comparison with the Camelus dromedaries sequence. A total of 28 putative phosphorylated motifs highlighted a complex heterogeneity and a potential variable degree of post-translational modifications. Ninety-six polymorphic sites were found through the comparison of the lama casein cDNAs with the homologous camel sequences, whereas the first description and characterization of the 5'- and 3'-regulatory regions allowed to identify the main putative consensus sequences involved in the casein genes expression, thus opening the way to new investigations -so far- never achieved in this species

Genetic polymorphism of goat CSN1S1 and CSN1S2 genes and their impact on milk composition

by means of selection based on parent genotyping at the DNA level it will be possible to obtain goat populations producing milk characterised by the absence of either as1-casein, or s2-casein or -casein. Such milk could be useful for specific technological processes of transformation or for specific nutritional or dietary purposes in order to attenuate the negative consequence of some metabolic deficiencies and allergies and to contribute to the prevention of some diseases Considering the remarkable quantitative polymorphism characterizing the main protein fractions encoding gene, some goat milk types are more similar to the woman milk and, therefore, could be used, with better results, in the human feeding. In fact, the woman milk possess particular characteristics. It is lacking in the -lactoglobulin fraction and it is characterized by a general low content in casein, in particular, as2 casein absence and as1 casein traces, similar to the milk produced by goats with genotype CSN1S2 0/0