Milk protein typing of bovine mammary gland tissue used to generate a complementary deoxyribonucleic acid library

Within- and between-Breed Selection Signatures in the Original and Improved Valachian Sheep

This study explored the genomic diversity and selection signatures in two Slovakian national breeds, the Original Valachian and the Improved Valachian sheep. As they are an important animal genetic resource within the country, but with decreasing population size, our aim is to identify potentially valuable genomic regions. A total of 97 sheep (18 male and 79 female) from the Original Valachian, and 69 sheep (25 male and 44 female) from the Improved Valachian populations were genotyped using the GeneSeek GGP Ovine 50 K chip. The inbreeding levels were assessed with runs of homozygosity (ROH). The selection signatures within breeds were identified based on the top 1% of most homozygous regions within the breed, the so-called ROH islands. The selection signatures between breeds were assessed based on variance in linkage disequilibrium. Overall, we have identified selection signatures with quantitative trait loci (QTL) and genes pointing towards all three production purposes of the Valachian sheep, milk, meat, and wool, including their quality characteristics. Another group with apparent large importance was the various traits related to health and resistance to parasites, which is well in line with the sturdy nature of this breed.

The influence of protein fractions from bovine colostrum digested in vivo and in vitro on human intestinal epithelial cell proliferation

Colostrum consists of a number of biologically active proteins and peptides that influence physiological function and development of a neonate. The present study investigated the biological activity of peptides released from first day bovine colostrum through in vitro and in vivo enzymatic digestion. This was assessed for proliferative activity using a human intestinal epithelial cell line, T84. Digestion of the protein fraction of bovine colostrum in vitro was conducted with the enzymes pepsin, chymosin and trypsin. Pepsin and chymosin digests yielded protein fractions with proliferative activity similar to that observed with undigested colostrum and the positive control foetal calf serum (FCS). In contrast trypsin digestion significantly (P<0·05) decreased colostral proliferative activity when co-cultured with cells when compared with undigested colostrum. The proliferative activity of undigested colostrum protein and abomasal whey protein digesta significantly increased (P<0·05) epithelial cell proliferation in comparison to a synthetic peptide mix. Bovine colostrum protein digested in vivo was collected from different regions of the gastrointestinal tract (GIT) in newborn calves fed either once (n=3 calves) or three times at 12-h intervals (n=3 calves). Digesta collected from the distal duodenum, jejunum and colon of calves fed once, significantly (P<0·05) stimulated cell proliferation in comparison with comparable samples collected from calves fed multiple times. These peptide enriched fractions are likely to yield candidate peptides with potential application for gastrointestinal repair in mammalian species.

Identification of the CSN1S1 allele in Indian goats by the PCR-RFLP method

The allelic distributions of the CSN1S1 (αs1-casein) in the Indian goats are quite different from European goat breeds. Majority of Indian goat breeds and non-descript goats carry A, B, E and F alleles at αs1-casein locus, as found by analysing both DNA and protein levels. However, A and B alleles, known to be associated with better casein yield, were observed in the highest proportion in all the Indian goat breeds. Gene frequency and breed heterozygosity were computed for the CSN1S1 gene. The gene frequency of allele A in Indian goats varies from 0.68 to 1.00 and allele B varies from 0.098 to 0.23. Allele F was observed in Beetal, Marwari, Chegu and non-descript goats of MP (Local MP) in less than 1% of population. The expected heterozygosity (He) varied from 0.141 to 0.506 over the population. The Beetal breed showed the highest gene diversity (0.506) followed by Jamunapari (0.395), Chegu (0.383) and Jakhrana (0.381) breeds. Therefore, the variability at CSN1S1 locus can be utilised for conservation as well as for genetic improvement of Indian goat breeds for increasing both the quality and quantity of milk production.

Characterization of casein gene complex and genetic diversity analysis in Indian goats

Milk protein polymorphism plays an important role in genetic diversity analysis, phylogenetic studies, establishing geographical diversity, conservation decision, and improving breeding goals. Milk protein polymorphism in Indian goat breeds has not been well studied; therefore, an investigation was carried out to analyze the genetic structure of the casein gene and milk protein diversity at six milk protein loci in nine Indian goat breeds/genetic groups from varied agro-climatic zones. Milk protein genotyping was carried out in 1098 individual milk samples by SDS-PAGE at alphaS1-CN (CSN1S1), beta-CN (CSN2), alphaS2-CN (CSN1S2), kappa-CN (CSN3), beta-LG, and alpha-LA loci. Indian goats exhibited alphaS1-casein A allele in higher frequency in the majority of breeds except Ganjam and local goats. The alphaS1-casein A allele frequencies varied from 0.45 to 0.77. A total of 16 casein haplotypes were observed in seven breeds and breed specific haplotypes were observed with respect to geographic region. The average number of alleles was lowest in Ganjam (1.66 +/- 0.81) and highest in Sirohi goats (2.50 +/- 1.05). Expected heterozygosity at six different loci demonstrated genetic diversity and breed fragmentation. Neighbor-Joining tree was built basing on Nei's distance. There was about 16.95% variability due to differences between breeds, indicating a strong subdivision. Principal component analysis was carried out to highlight the relationship among breeds. The variability among goat breeds was contributed by alphaS2-CN, beta-LG and alphaS1-CN. The Indian goats exhibited alphaS1-CN (CSN1S1) A allele in higher frequency in all the breeds indicating the higher casein yield in their milk.

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.

Polymorphism of β-lacto globulin gene in Indian goats and its effect on milk yield

Polymorphism in the beta-LG gene in the Indian goat was investigated by the SDS-PAGE and PCR-RFLP method. SDS-PAGE was carried out in 1098 samples belonging to 8 different breeds of Indian goats. The electrophoretic pattern in the beta-LG locus showed the presence of AA and AB genotypes with frequencies of 0.81 and 0.19, 0.89 and 0.11, 0.50 and 0.50, 0.80 and 0.20, 0.84 and 0.16, 1.00 and 0.00, 0.98 and 0.02 and 0.950 and 0.050 in Jamunapari, Barbari, Marwari, Sirohi, Jakhrana, Beetal, Local UP and Local MP goats, respectively. A total of 358 individuals belonging to 13 different genetic groups were analyzed by the PCR-RFLP method. The amplified product was observed as 426 bp and the restriction digestion with SacII revealed three genotypes, namely S1S1, S1S2 and S2S2 at the beta-LG locus. The frequency of the S2S2 genotype ranged from 0.42 to 1.00 in the population. An analysis was carried out in Jamunapari and Barbari goats to observe the effect of the beta-LG genotype on 90-day milk yield. Least squares analysis of data showed that beta-LG AA animals had higher milk yield than the beta-LG AB genotype in both breeds (P < 0.01).

Characterization of two new alleles at the goat CSN1S2 locus

Two novel alleles at the goat CSN1S2 locus have been identified: CSN1S2(F) and CSN1S2(D). Sequence analyses revealed that the CSN1S2(F) allele is characterized by a G --> A transition at the 13th nucleotide in exon 3 changing the seventh amino acid of the mature protein from Val to Ile. The CSN1S2(D) allele, apparently associated with a decreased synthesis of alpha s2-casein, is characterized by a 106-bp deletion, involving the last 11 bp of the exon 11 and the first 95 bp of the following intron. Methods (PCR-RFLP and PCR) for identification of carriers of these alleles have been developed.

Expression and purification of glycosylated bovine beta-casein (L70S/P71S) in Pichia pastoris

Post-translational glycosylation of bovine beta-casein (L70S/P71S) that results in Asn(68)-linked glycan on the protein was obtained in up to 30% of total beta-casein expressed in the methylotrophic yeast Pichia pastoris. Among the growth/induction media used, buffered minimal glycerol (BMG)/buffered minimal methanol (BMM) media were best for the production of glycosylated bovine beta-casein, indicating pH-dependent glycosylation. Glycosylated bovine beta-casein (L70S/P71S) expressed in P. pastoris was purified to homogeneity by the combination of ammonium sulfate fractionation, Concanavalin A--Sepharose affinity column, and Mono Q anion-exchange FPLC. The purified glycosylated bovine beta-casein was specific only to Concanavalin A, and the oligosaccharide structure of glycosylated beta-casein was of high-mannose type. Unlike the hyperglycosylation that occurred in yeast, the majority of bovine beta-casein was not hyperglycosylated in P. pastoris, and its molecular weight was estimated to be 33.6 kDa. Glycosylated bovine beta-casein was normally phosphorylated to the same degree as native bovine beta-casein.

Cation-exchange purification of mutagenized bovine beta-casein expressed in transgenic mouse milk: its putative Asn68-linked glycan is heterogeneous

Bovine beta-casein (A2 genetic variant) was mutagenized to (L70S/P71S) and expressed in transgenic mouse milk. This protein now carries the signal (N68S69S70S71) that mimics a consensus eukaryotic glycosylation signal (N-X-S/T) (3). Hypothetically this protein should be glycosylated at N68 by any eukaryotic organism producing it. This novel protein was purified from transgenic mouse milk by Mono-S cation-exchange fast protein liquid chromatography (FPLC). The novel beta-casein was separated without cross contamination from mouse caseins by using acetate buffer (pH 5.0) in the presence of 6 M urea, octyl-glucopyranoside and 2-beta-mercaptoethanol. The purified (L70S/P71S) beta-casein showed an N-linked oligosaccharide attached to Asn68 and different lectin binding profiles compared with the same protein expressed in yeast. The mouse-expressed beta-casein (L70S/P71S) was specific to Concanavalin A, wheat germ agglutinin, Erythrina cristagalli agglutinin, and Ulex europaeus, indicating its oligosaccharide structure is different in the mammary gland of mouse than the reported glycosylated beta-casein expressed in Pichia pastoris (4). In addition, the five serine residues located at amino terminus of wild type bovine beta-casein were shown to be normally phosphorylated as in native bovine beta-casein.

Polymorphisms of bovine beta-lactoglobulin promoter and differences in the binding affinity of activator protein-2 transcription factor

Differential production of the two most common allelic variants of beta-lactoglobulin (LG), beta-LG A and beta-LG B, has been observed using PAGE. This study evaluated 733 bp of the beta-LG promoter region and 92 bp of the first exon for possible polymorphisms using denaturing gradient gel electrophoresis and nucleotide sequence analysis. Within this region, 13 single nucleotide substitution polymorphisms were detected. Twelve polymorphisms were allele specific, and one appeared to be polymorphic only for the B allele. Several potential binding sites for transcription factors were found within the promoter sequence. This study investigated the role of the G to C transversion within a consensus binding site for activator protein-2 at position-430 bp upstream from the transcription initiation site. Using the DNase-I footprint assay, we confirmed the functional importance of this point mutation and showed different binding affinities of activator protein-2 for both alleles. We discuss the possible regulatory role of activator protein-2 in the transcriptional regulation of the beta-LG gene and propose the activator protein-2 transcription factor as a modulator of gene expression of beta-LG.

Differential allelic expression of lactoproteins: a model to study transcriptional regulation

The importance of transcriptional control of gene expression has been documented in relation to several genetic defects in man. Mutations in the promoter region of genes have been shown to be responsible for defects which are characterized by over or under expression of genes. Genetic polymorphisms of the milk protein genes, and their high level of tissue specific expression during lactation, represent a suitable system for studying regulation of gene expression. Quantification of the allele specific protein products has demonstrated unequal allelic contribution in the expression of the beta lactoglobulin (beta-LG) alleles A and B. The DNA sequence analysis of the beta-LG promoter revealed allele specific polymorphisms related to the coding region genotypes.

Separation of beta-casein A1, A2, and B using cation-exchange fast protein liquid chromatography

beta-Casein genetic variants A1, A2, and B were separated using cation-exchange fast protein liquid chromatography. beta-Casein from a herd bulk casein sample eluted as a series of three peaks. Casein samples from individual cows containing known combinations of beta-casein A1, A2, and B were used to confirm that the three peaks were beta-casein genetic variants. An acid-PAGE gel confirmed the identity of the peaks that eluted from the column.

Cloning and sequencing of a complementary deoxyribonucleic acid coding for a bovine alpha s1-casein A from mammary tissue of a homozygous B variant cow

A cDNA clone for bovine alpha s1-casein variant A was isolated from a mammary gland cDNA library using a synthetic degenerate oligonucleotide probe. The largest Pst I insert containing an EcoR I site was sequenced. It contained 1090 base pairs, 47 in the 5' noncoding region, 603 in the coding region and 440 in the 3' noncoding region. The nucleotide sequence was compared with three published cDNA sequences for alpha s1-casein variant B. The most obvious difference was the absence of the 39 bases encoding the 13 amino acids that are present in the B variant but absent from the A variant. In addition, five other single base positions differed within individual codons among the four sequences at the third base for each codon, but this did not change the amino acids encoded. There were, however, a number of differences found in the 3' noncoding region. The isolated cDNA was subjected to site-directed mutagenesis to replace a Val-Ile dipeptide with Phe-Phe to increase the chymosin sensitivity of the protein. When the milk proteins from mammary gland tissue extracts were typed, the alpha s1-casein A gene product was not detected.