Kappa-casein polymorphisms among cattle breeds and bison herds

Summary
We identified the Hind III restriction site polymorphism of K-casein in cattle reported by Pinder et al. ( Animal Genetics 22, 11, 1991) and found an additonal polymorphism ( Rsa I) in cattle and bison. The Hin dIII and Rsa I restriction sites were mapped and three haplotypes (alleles) were identified. Preliminary screening of 39 cattle and 71 bison revealed one allele restricted to cattle, one restricted to bison, and one shared by the species. No fixed allelic differences were observed among cattle breeds or among bison herds or subspecies.     

Biochemical characterization of the bovine genetic K-casein C and E variants

Analysis of elution profiles of enzymatic and CNBr digests of K-caseins C and E, and sequencing of most relevant peptides allowed the chemical characterization of both genetic variants. They differ from their B and A allelic counterparts by a single substitution, His97/Arg and Gly155/Ser, respectively. Electrophoretic behaviour of the investigated C and E variants was in good agreement with the observed amino acid replacements.     

Detection of bovine αs1-casein genomic variants using the allele-specific polymerase chain reaction

A method was developed to distinguish between genotypic variants B and C of bovine alpha s1-casein, using the allele-specific polymerase chain reaction (ASPCR). The alpha s1-casein genotype determined for 17 Jersey cows by the ASPCR method was confirmed by typing the alpha s1-casein milk proteins on isoelectric focusing gels. Using the ASPCR method described, rapid analysis of the alpha s1-casein genotype of bulls is now possible. In addition, kappa-casein genotypes can be determined from the same PCR reaction.     

Identification of bovine K-casein genotypes at the DNA level

By using a bovine kappa-Cn cDNA as probe and the PstI endonuclease we demonstrate that the DNA restriction patterns of kappa-Cn AA and kappa-Cn BB cows are different. Besides two invariant fragments (about 6.8kb and 1.1kb) the former shows two fragments of about 4.3 kb and 0.3 kb and the latter one fragment of about 4.6 kb. kappa-Cn AB cows show intermediate pattern. Therefore, it is possible to determine the bovine kappa-Cn genotypes even in absence of gene product.     

Cloning and sequencing of the porcine K-casein cDNA

cDNA clones encoding porcine kappa-casein were isolated and sequenced. The porcine kappa-casein cDNA is 851 bp in length and encodes a preprotein of 188 amino acids.     

A microsatellite within the bovine K-casein gene reveals a polymorphism correlating strongly with polymorphisms previously described at the protein as well as the DNA level

The polymorphism of a (TA)n(CA)n repeat microsatellite present in the third intaron of the bovine K-casein gene (CASK) has been investigated. The existence of six alleles differing only in the number of dinucleotide repeats has been established. A total of 330 animals belonging to nine different pure bred Bos Taurus French breeds or to a cross-bred Bos taurus*Bos indicus population (Créole) were genotyped. The distribution of the microsatellite alleles was examined and clear breed differences were noted. Genotyping of animals by isoelectric focusing (IEF) or restriction fragment length polymorphism (RFLP) (TaqI) was performed, in order to examine the relationship of the microsatellite polymorphism to other previously described CASK polymorphisms, at the protein and DNA levels. Strong correlation was seen, indicating that evolution of the various polymorphisms was not independent, and nine CASK haplotypes were observed.     

Genetic variation in domestic reindeer and wild caribou in Alaska

Reindeer ( Rangifer tarandus tarandus ) were introduced into Alaska 100 years ago and have been maintained as semidomestic livestock. They have had contact with wild caribou ( R. t. granti ) herds, including deliberate crossbreeding and mixing in the wild. Reindeer have considerable potential as a domestic animal for meat or velvet antler production, and wild caribou are important to subsistence and sport hunters. Our objective was to quantify the genetic relationships of reindeer and caribou in Alaska. We identified allelic variation among five herds of wild caribou and three herds of reindeer with DNA sequencing and restriction enzymes for three loci: a DQA locus of the major histocompatibility complex ( Rata-DQA1 ), K-casein and the D-loop of mitochondrial DNA. These loci are of interest because of their potential influence on domestic animal performance and the fitness of wild populations. There is considerable genetic variation in reindeer and caribou for all three loci, including five, three and six alleles for DQA , K-casein and D-loop respectively. Most alleles occur in both reindeer and caribou, which may be the result of recent common ancestry or genetic introgression in either direction. However, allele frequencies differ considerably between reindeer and caribou, which suggests that gene flow has been limited.     

Detection of a new K-casein variant in cow''s milk

In German Simmental cattle a new kappa-casein variant was detected by isoelectric focusing, which cannot be distinguished from kappa-casein A by polyacrylamide and starch gel electrophoresis. It was named kappa-casein D. The frequencies of kappa-casein alleles were kappa-Cn A 0.75, kappa-Cn B 0.24, kappa-Cn D 0.01.