Characterization of the casein gene complex in West African goats and description of a new alpha(s1)-casein polymorphism.

The analysis of casein polymorphisms was carried out in West Africa goat populations: Red Sokoto (n = 57), West African Dwarf Nigeria (n = 27), West African Dwarf Cameroon (n = 39), and Borno (n = 37). The 4 casein genes alpha(s1) (CSN1S1), beta (CSN2), alpha(s2) (CSN1S2), and kappa (CSN3) were typed at the DNA level. No null alleles were found in any of the genes analyzed. A PCR single-strand conformation polymorphism method was implemented for the identification of CSN1S1*F allele simultaneously with A/0(1), B/E, N and the new allele. The allele differed from CSN1S1*B by a synonymous transversion TCG-->TCT in the codon corresponding to Ser(66) of the mature protein. The new allele, named CSN1S1*B', occurred at a high frequency in all the populations, ranging from 0.295 (West African Dwarf Cameroon) to 0.405 (Borno). A greater frequency was found for alleles associated with high alpha(s1)-casein quantity, as has already been observed in the goat populations from the Mediterranean area. The intermediate E allele occurred only in the Red Sokoto and at a low frequency. The faint F allele occurred in 3 populations at frequencies lower than 0.03. Linkage disequilibrium occurred in all the populations, with highly significant differences in Borno, Red Sokoto, and West Africa Dwarf Nigeria, and significant differences in West Africa Dwarf Cameroon. Only 10 haplotypes showed frequencies > or =0.05 in at least 1 of the 4 populations considered, and the overall frequency was >0.1 only for 4 haplotypes: BAAB, B'ACA, ACAB, and BACA (in the order CSN1S1-CSN2-CSN1S2-CSN3). Haplotype BAAB, postulated as an ancestral haplotype in previous studies, was the most common haplotype in all breeds except Borno, where B'ACA was predominant. The results obtained are of considerable significance given that very little information exists on the subject for African goats. The high frequency of strong alleles in the calcium-sensitive caseins as well as the high linkage disequilibrium found among the casein genes in the African breeds analyzed may suggest that specific casein haplotypes have already been selected due to their advantages for nutrition. Haplotypes providing greater protein and casein content would increase the energy content of milk, thus resulting in more favorable growth and survival of young goats and humans consuming the milk.

Caroli A ，Chiatti F ，Chessa S ，Rignanese D ，Ibeagha-Awemu EM ，Erhardt G ... -  《-》

Focusing on the goat casein complex.

The analysis of casein polymorphisms in goat species is rather difficult, because of a large number of mutations at each locus, and the tight linkage involving the 4 casein genes. Three goat breeds from Northern Italy, Orobica, Verzasca, and Frisa, were analyzed at the casein complex by milk isoelectrofocusing and analyses at the DNA level to identify the majority of all known polymorphisms. The casein gene structure of the 3 local breeds at alpha(S1)-casein (CSN1S1), beta-casein (CSN2), alpha(S2)-casein (CSN1S2), and kappa-casein (CSN3) was compared with that of Camosciata, a more widely distributed breed. A new allele was identified and characterized at CSN2 gene, which seemed to be specific to the Frisa breed. It was named CSN2*E, and was characterized by a transversion TCT --> TAT responsible for the amino acid exchange Ser(166) --> Tyr(166) in the mature protein. The casein haplotype structure is highly different among breeds. A total of 26 haplotypes showed a frequency higher than 0.01 in at least 1 of the 4 breeds considered, with 12, 3, 5, and 19 haplotypes in Frisa, Orobica, Verzasca, and Camosciata breeds, respectively. Only 13 haplotypes occurred at a frequency higher than 0.05 in at least 1 breed. With the molecular knowledge of each locus, the ancestral haplotype coding for CSN1S1*B, CSN2*A, CSN1S2*A, and CSN3*B protein variants can be postulated. A protein evolutionary model considering the whole casein haplotype is proposed.

Caroli A ，Chiatti F ，Chessa S ，Rignanese D ，Bolla P ，Pagnacco G ... -  《-》

Divergence at the casein haplotypes in dairy and meat goat breeds.

Casein genes have been proved to have an influence on milk properties, and are in addition appropriate for phylogeny studies. A large number of casein polymorphisms exist in goats, making their analysis quite complex. The four casein loci were analyzed by molecular techniques for genetic polymorphism detection in the two dairy goat breeds Bunte Deutsche Edelziege (BDE; n=96), Weisse Deutsche Edelziege (WDE; n=91), and the meat goat breed Buren (n=75). Of the 35 analyzed alleles, 18 were found in BDE, and 17 in Buren goats and WDE. In addition, a new allele was identified at the CSN1S1 locus in the BDE, showing a frequency of 0.05. This variant, named CSN1S1*A', is characterized by a t-->c transversion in intron 9. Linkage disequilibrium was found at the casein haplotype in all three breeds. A total of 30 haplotypes showed frequencies higher than 0.01. In the Buren breed only one haplotype showed a frequency higher than 0.1. The ancestral haplotype B-A-A-B (in the order: CSN1S1-CSN2-CSN1S2-CSN3) occurred in all three breeds, showing a very high frequency (>0.8) in the Buren.

Küpper J ，Chessa S ，Rignanese D ，Caroli A ，Erhardt G ... -  《-》

Focusing on casein gene cluster and protein profile in Garganica goat milk.

A survey was carried out in eight goat dairy farms, a total of 71 individual Garganica goat milk samples were collected for genomic DNA extraction. Casein alleles and haplotype frequencies of Garganica population were estimated. Individual milks were also analysed for chemical composition, rheological properties, and protein profile. The strong A* allele of CSN1S1 was predominant in the population investigated, the weak allele F of CSN1S1 showed a relatively high frequency and the null alleles N and 01 were first observed in this breed. At CSN1S2 locus the strong A* allele was the most frequent, followed by the F allele and the null allele. The strong A* allele was predominant at CSN2 locus, and relatively high incidence of null allele 0 was observed. CSN3 locus was monomorphic for B* allele. The exact test of sample differentiation based on haplotype frequencies discriminate the farms into two groups characterized by the highest frequency of strong (S-CSN1S1) or weak (W-CSN1S1) alleles at CSN1S1. Protein and casein contents were higher in the group characterized by strong allele than in the group with weak allele at CSN1S1. The 2D electrophoresis technique was performed to screen goat casein variability at the protein level and to evaluate global casein genotype (alphas1, alphas2, beta and kappa-CN). Gels displayed the protein profile associated with casein genotype, and demonstrated differences in the protein expression deriving from interactions between loci. The variability of goat casein loci in Garganica goat breed could be exploited to differentiate the population on the basis of milk utilization and could represent a strategy to preserve the genotype of this autochthonous breed.

Albenzio M ，Santillo A ，d'Angelo F ，Sevi A ... -  《JOURNAL OF DAIRY RESEARCH》

Casein haplotype structure in five Italian goat breeds.

The aim of this work was to investigate the genetic structure of the casein gene cluster in 5 Italian goat breeds and to evaluate the haplotype variability within and among populations. A total of 430 goats from Vallesana, Roccaverano, Jonica, Garganica, and Maltese breeds were genotyped at alphas1-casein (CSN1S1), alphas2-casein, (CSN1S2), beta-casein (CSN2), and kappa-casein (CSN3) loci using several genomic techniques and milk protein analysis. Casein haplotype frequencies were estimated for each breed. Principal component analysis was carried out to highlight the relationship among breeds. Allele and haplotype distributions indicated considerable differences among breeds. The haplotype CSN1S1*F- CSN1S2*F-CSN3*D occurred in all breeds with frequencies >0.100 and was the most common haplotype in the Southern breeds. A high frequency of CSN1S1*0-CSN1S2*C-CSN3*A haplotype was found in Vallesana population (0.162). Principal component analysis clearly separated the Northern and Southern breeds by the first component. The variability of the caprine casein loci and variety of resulting haplotypes should be exploited in the future using specific breeding programs aiming to preserve biodiversity and to select goat genetic lines for specific protein production.

Sacchi P ，Chessa S ，Budelli E ，Bolla P ，Ceriotti G ，Soglia D ，Rasero R ，Cauvin E ，Caroli A ... -  《JOURNAL OF DAIRY SCIENCE》