Genetic and protein polymorphism at CSN1S1 locus in two goat breeds.

Genetic polymorphisms of casein have received a considerable research effort formany years because of its potential effect on milk composition. Milk composition,specifically protein content, differs quantitatively and qualitatively among speciesand also among breeds and individuals. Sicilian goat breeds seem to be an interestingmodel since they have never been under a selection program, and therefore may carryunique casein polymorphisms. Moreover, the importance of goat milk in infant dietsis growing probably because goat milk in some cases is less allergenic than cow milk.It is important to evaluate the genetic polymorphisms at the CSN1S1 locus in thepopulations of interest, like the Girgentana or Maltese goat breeds, because caseinsare considered as the main cause of allergic reactions. Moreover CSN1S1polymorphisms have been associated to different levels of this proteinexpression in milk. The goal of the present research was twofold 1) to genotypeCSN1S1 locus, and 2) to type casein protein polymorphisms in two Sicilianbreeds, Maltese and Girgentana. Blood and milk samples were obtained from400 animals (200 of each breed) located in four different flocks. DNA wasextracted from leucocytes and CSN1S1 polymorphisms were detected by PCRfollowed by restriction fragment length polymorphism (PCR-RFLP), and byallele specific PCR (AS-PCR). PCR and digestion products were analyzed byelectrophoresis in 3% agarose gel stained with ethidium bromide after exposureto ultraviolet light. Milk samples, from the same individuals, were analysed forprotein expression by isoelectrofocusing (IEF). IEF was carried out over a 2.5-6.0 pH gradient. Protein separation was performed in a polyacrylamide gel, andstained with Coomassie Brilliant Blue G250. Results showed a high percentageof A and B alleles (considered strong alleles), but also the presence of weak (F)and null alleles (N) was found in both breeds. The results may have practicalimplications to plan a selection program given that animals with allele A and Bmight be useful for cheese production since these animals express more caseinthan those carrying F or N alleles, and animals that do not express casein mightbe beneficial for hypoallergenic milk production.