Polymorphisms of beta-lactoglobulin promoter region in three Sicilian goat breeds

Whey protein polymorphisms in Sudanese goat breeds

The aim of the present study was to assess genetic variation that is characteristic for Sudanese goat breeds in the milk whey protein genes (LALBA and BLG). Four Sudanese goat breeds were screened for variability in LALBA and BLG genes at the DNA level by comparative sequencing of five animals per breed. Sixteen SNPs were identified in LALBA: seven in the upstream region, six synonymous, and three in the 3´-UTR. Three novel synonymous SNPs in exon 2 (ss5197800003, ss5197800012, and ss5197800004) were found in Nubian, Desert, and Nilotic, but not in Taggar goats. One SNP in the promoter of LALBA (rs642745519) modifies a predicted transcription factor binding site for Tcfe2a. The SNPs in the 3'-UTR (rs657915405, rs641559728, and rs664225585) affect predicted miRNA target sites. With respect to haplotypes in the exonic region, haplotype LALBA-A is most frequent in Nubian, Desert, and Nilotic goats, while haplotype LALBA-D is prevalent in Taggar goats. In BLG, 30 SNPs were detected: eight in the upstream gene region, two synonymous, 17 intronic, and three in the 3'-UTR. Among the 30 identified SNPs, 15 were novel. Four of these novel SNPs were located in the upstream gene region, one was synonymous, and ten were intronic. The novel synonymous SNP (ss5197800017), located in exon 2, was only found in Nubian and Nilotic goats. The SNPs ss5197800010 and rs635615192 in the promoter are located in predicted binding sites of transcription factors (M6097, Elk3, Elf5, and GABPA). Among seven haplotypes detected in the coding region, haplotype BLG-A is most frequent in Nubian and Nilotic goats while haplotype BLG-B is most frequent in Desert and Taggar goats. The high variability in regulatory gene regions among Sudanese goats could potentially affect the quality and yield of whey proteins in goat milk and provide a wide resource for genetic improvement of milk production and milk technology characteristics.

Differential Expression of the Alpha S1 Casein and Beta-Lactoglobulin Genes in Different Physiological Stages of the Adani Goats Mammary Glands

Background

Milk proteins genes have been the focus of the researches as the candidate target genes that play a decisive role when animal breeding is desired.

Objectives

In the present study, the transcriptional levels of Beta-lactoglobulin (BLG) and Alpha S1 casein (CSN1S1) genes were investigated during prenatal, milking and drying times in mammary glands of the Adani goats which showed high and low breeding values.

Materials and Methods

The breeding values of the animals were estimated first by applying multi-trait random regression model. Using the biopsy gun, the mammary gland samples were taken and real-time PCR was applied to search the expression of the genes. Fixed factors of the model were the breeding value groups, sampling times and their interactions.

Results

The interactions were significant for both genes. At milking time, the high breeding value group exhibited more transcriptional levels for BLG and less transcriptional levels for CSN1S1 gene compared with the low breeding value group. The expression patterns of these genes were also different between the two breeding value groups. The maximum level of BLG and CSN1S1 transcriptions were found to occur at drying time.

Conclusions

A difference in the gene expression was observed between the two groups which indicate the change in the nucleotide sequence for transcription factor binding sites, or miRNA binding sites, otherwise in the coding regions. Therefore, the variations in the coding and promoter regions of this gene should be investigated in the further studies.

Longitudinal data analysis of polymorphisms in the κ-casein and β-lactoglobulin genes shows differential effects along the trajectory of the lactation curve in tropical dairy goats

The κ-casein (CSN-3) and β-lactoglobulin (BLG) genes are extensively polymorphic in ruminants. Several association studies have estimated the effects of polymorphisms in these genes on milk yield, milk composition, and cheese-manufacturing properties. Usually, these results are based on production integrated over the lactation curve or on cross-sectional studies at specific days in milk (DIM). However, as differential expression of milk protein genes occurs over lactation, the effect of the polymorphisms may change over time. In this study, we fitted a mixed-effects regression model to test-day records of milk yield and milk quality traits (fat, protein, and total solids yields) from Colombian tropical dairy goats. We used the well-characterized A/B polymorphisms in the CSN-3 and BLG genes. We argued that this approach provided more efficient estimators than cross-sectional designs, given the same number and pattern of observations, and allowed exclusion of between-subject variation from model error. The BLG genotype AA showed a greater performance than the BB genotype for all traits along the whole lactation curve, whereas the heterozygote showed an intermediate performance. We observed no such constant pattern for the CSN-3 gene between the AA homozygote and the heterozygote (the BB genotype was absent from the sample). The differences among the genotypic effects of the BLG and the CSN-3 polymorphisms were statistically significant during peak and mid lactation (around 40-160 DIM) for the BLG gene and only for mid lactation (80-145 DIM) for the CSN-3 gene. We also estimated the additive and dominant effects of the BLG locus. The locus showed a statistically significant additive behavior along the whole lactation trajectory for all quality traits, whereas for milk yield the effect was not significant at later stages. In turn, we detected a statistically significant dominance effect only for fat yield in the early and peak stages of lactation (at about 1-45 DIM). The longitudinal analysis of test-day records allowed us to estimate the differential effects of polymorphisms along the lactation curve, pointing toward stages that could be affected by the gene.

Variability of the caprine whey protein genes and their association with milk yield, composition and renneting properties in the Sarda breed: 2. The BLG gene

The variability of the promoter region and the 3'UTR (exon-7) of the BLG gene, encoding the β-lactoglobulin, was investigated by sequencing in 263 lactating Sarda goats in order to assess its association with milk traits. Milk traits included: milk yield, fat, total protein and lactose content, pH, daily fat and protein yield (DFPY), freezing point, milk energy, somatic cell count, total microbial mesophilic count, rennet coagulation time (RCT), curd firming rate (k20) and curd firmness (a30). A total of 7 polymorphic sites were detected and the sequence analysed was given accession number KM817769. Only three SNPs (c.-381C>T, c.-323C>T and c.*420C>A) had minor allele frequency higher than 0.05. The effects of farm, stage of lactation and the interaction farm × stage of lactation significantly influenced all the milk traits (P T and c.*420C>A (P T (P < 0.001). The c.-381TT homozygous goats showed lower pH, RCT and k20 than c.-381CT (P < 0.05). In conclusion the polymorphism of the goat BLG gene did not affect the total protein content of the Sarda goat milk, and only weakly influenced RCT and k20. On the other hand, an interesting effect on milk yields and DFPY emerged in two SNPs. This information might be useful in dairy goat breeding programs.

Comparative protein composition analysis of goat milk produced by the Alpine and Saanen breeds in northeastern Brazil and related antibacterial activities

The protein composition of goat milk differs between goat breeds and could present regional trends. The aim of this study was to comparatively analyze the protein composition of goat milk produced by the Alpine and Saanen breeds in northeastern Brazil and to evaluate the antibacterial activity of its protein fractions. SDS-PAGE, 2-DE electrophoresis and RP-HPLC analyses revealed the absence of αs1-casein in the milk of both breeds and no differences between the αs2-casein, β-casein, β-lactoglobulin and α-lactalbumin profiles. The amounts of soluble proteins and β-casein hydrolysis residues were higher in Saanen milk. Only the protein fraction containing the largest amounts of casein (F_60–90%) inhibited bacterial growth, with MIC values between 50 and 100 mg/mL. This study describe for the first time three important points about the goat milk protein of two Brazilian goat breeders: absence of α-s1 casein in the protein profile, differences between the milk protein composition produced by goats of Alpine and Saanen breeders and antibacterial activity of unbroken proteins (casein-rich fraction) present in these milk.