Genetic polymorphism of milk proteins in African Bos taurus and Bos indicus populations. Characterization of variants αs1-Cn H and κ-Cn J

Abstract

The polymorphism of caseins, a-lactalbumin and &beta;-lactoglobulin was investigated in African Bos taurus (N'Dama, Baoulé, Kuri) and Bos indicus (Shuwa Arab, Sudanese Flzlani) populations. The respective frequencies of alleles a sl-Cn B and a sl-Cn c in the N'Dama (0.89 and 0.11) and Baoulé (0.92 and 0.08) breeds were almost opposite to those found in the Shuwa Arab zebu (0.22 and 0.78), a true zebu, which confirms a phenomenon already documented in the literature. Because the a sl-Cn B , / 3-Cn Al , <t-Cn haplotype was strongly predominant in N'Dama and Baoul é (0. 56 and 0. 60), as compared to the asl-C n C , / 3_C D A2 , K-Cn! haplotype in the Shuwa Arab zebu (0.63), an opposite trend in frequencies was also observed between taurines and zebus at the &beta;-Cn and rc-Cn loci. These results confirm that the polymorphism of caseins provides an efficient marker system to discriminate Bos taurus from Bos indicus origins. The Kuri was at an intermediate position, since, in this population, the a sl-Cn B allele predominated as in taurines, while the * Correspondence and reprints E-mail: jngroscl@biotec.jouy.inra J r a sl-Cn C , /3-Cn A2 , K-Cn A haplotype was the most frequent, as in zebus. This may be interpreted as revealing intercrossings with zebus in the previous history of this cattle type. Conversely, but to a lesser degree, the polymorphism of the Sudanese Fulani zebu indicates a taurine influence, in accordance with what is accepted about the origins of this cattle type. No polymorphism of a s2-casein could be identified, while a-lactalbumin was polymorphic in all populations. Two additional variants, probably specific to African cattle, were observed. Variant H of a sl-casein, found in Kuri, is characterized by the deletion of the eight amino acid residues (51-58) coded by exon 8, a probable consequence of exon skipping. Allele &OElig;s l-Cn H is derived from allele a sl-Cn B. Variant J of !-casein, found in Baoulé, is derived from variant B by the substitution of Ser 155 (B)-Arg (J). The existence of at least another allele of a sl-casein was suggested. &copy; Inra/Elsevier, Paris genetic polymorphism / milk proteins / Africa / Bos taurus / Bos indicus Résumé-Polymorphisme génétique des protéines du lait dans des populations de taurins et de zébus africains. Caractérisation des variants a sl-Cn H et K-Cn J. Le polymorphisme des caséines, de l'a-lactalbumine et de la ¡ 3-lactoglobuline a été analysé dans des populations bovines africaines de type taurin (N'Dama, Baoulé, Kouri) et zébu (Choa, Peuhl). Les fréquences respectives des allèles a s1-Cn B et a, l-Cn c chez les taurins N'Dama (0,89 et 0,11) et Baoulé (0,92 et 0,08) tendent à être inverses de celles trouvées chez le zébu Choa, un zébu vrai (0,22 et 0,78), ce qui confirme un phénomène déjà signalé dans la littérature. L'haplotype a sl-Cn B @ ¡3-Cn Al , r,-Cn B prédominant nettement chez ces taurins (0,56 et 0,60), par contraste à l'haplotype a sl-Cn c , ¡3-Cn A2 , /'i;-Cn A chez le zébu Choa (0,63), l'inversion des fréquences entre taurins et zébus...

Geographic distribution of haplotype diversity at the bovine casein locus

“…The observation that casein haplotype frequencies are geographically distributed is in accordance to the findings of former studies based on protein polymorphism [7,23,28]. Mahé et al [28] described the predominance of a haplotype on the basis of three casein genes CSN1S1*C-CSN2*A 2 -CSN3*A in zebu breeds.…”

“…Mahé et al [28] described the predominance of a haplotype on the basis of three casein genes CSN1S1*C-CSN2*A 2 -CSN3*A in zebu breeds. However, the electrophoretic methods they used does not allow the discrimination between CSN3*H and CSN3*A I from CSN3*A. Consequently, the occurrence of haplotypes CA 2 A I and CA 2 H, which are within BCA 2 AA I , CCA 2 AA I , BCA 2 AH, and CCA 2 AH, is in agreement with these findings and indicates the introgression of Bos indicus in southern and eastern European cattle breeds.…”

“…Therefore casein genes could be subject to natural and artificial selection [47]. Polymorphisms in the casein genes allow the determination of casein haplotypes, which can be used for studies concerning quantitative traits [14,22,45] or phylogeny [7,28] since they provide more information than the individual genes [21]. Novel casein variants at CSN2 [18] and CSN3 [16,37,38] have been described recently, but up to now it has not been clear how these are linked within the haplotypes.…”

Genetic diversity measures of local European beef cattle breeds for conservation purposes

“…Studies have been undertaken on a broad scale to encompass populations not only from different regions of the globe but also at a local level among closely related populations within particular regions [4,18,22,30,33,38]. Manwell and Baker [31] were the first to present a phylogenetic tree for the ten major cattle breed-groups of Europe, Western Asia, and Northern Africa.…”

Genetic diversity, introgression and relationships among West/Central African cattle breeds

“…MacHugh et al [25] in a study on cattle breeds from Africa, Europe and India reported the highest diversity levels in African Bos indicus breeds, which are comparable to diversity levels at a center of origin [22]. The admixed nature of African Bos indicus breeds is thought to be responsible for its increased level of diversity [26]. It is therefore necessary to assess diversity levels in more breeds in the region in order to determine improvement and conservation priorities.…”