Variations in Casein Genes Are Associated with Milk Protein and Fat Contents in Sarda Goats (Capra hircus), with an Important Role of CSN1S2 for Milk Yield

This work aimed to assess the variability of casein genes in a population of 153 bucks and 825 lactating does of the Sarda breed, and to perform association analysis between polymorphic sites and milk yield and composition traits. To genotype the casein genes, we chose an SNP panel including 44 SNPs mapping to the four casein genes CSN1S1, CSN2, CSN1S2, and CSN3. Genotyping (made by KASP™ genotyping assay, based on competitive allele-specific PCR) revealed the high variability of the Sarda goat, and haplotype analysis revealed linkage disequilibrium (LD) between CSN1S1 and CSN2 genes, in addition to two LD blocks within the CSN1S2 and two LD blocks within the CSN3 gene, in bucks and does. Association analysis revealed that variability at all four casein genes was associated with milk protein content, total solids, and milk energy. The three Ca-sensitive casein genes were associated with lipid content, and CSN1S2 showed a unique pattern, with intron variants associated with milk yield, in addition to milk pH, NaCl, and SCS (Somatic Cell Score). This information might prove useful in selection schemes and in future investigations aiming to better understand the biology of lactation, and the direct link between genotype and phenotype.

Genetic Diversity in Casein Gene Cluster in a Dromedary Camel (C. dromedarius) Population from the United Arab Emirates

Genetic polymorphisms, causing variation in casein genes (CSN1S1, CSN1S2, CSN2, and CSN3), have been extensively studied in goats and cows, but there are only few studies reported in camels. Therefore, we aimed to identify alleles with functional roles in the United Arab Emirates dromedary camel (Camelus dromedarius) population to complement previous studies conducted on the same species. Using targeted next-generation sequencing, we sequenced all genes in the casein gene cluster in 93 female camels to identify and characterize novel gene variants. Most variants were found in noncoding introns and upstream sequences, but a few variants showed the possibility of functional impact. CSN2 was found to be most polymorphic, with total 91 different variants, followed by CSN1S1, CSN3 and CSN1S2. CSN1S1, CSN1S2 and CSN2 each had at least two variants while CSN3 had only one functional allele. In future research, the functional impact of these variants should be investigated further.

Transcripts and protein levels of CSN1S1 and CSN3 genes in dairy cattle mammary gland secretory tissue during chronic staphylococcal infection

Our objective was to determine the influence of chronic coagulase-positive staphylococci (CoPS) or coagulase-negative staphylococci (CoNS) infection on the mRNA and protein levels of two main milk proteins responsible for cheese curd quantity and quality, alpha-S1-casein (CSN1S1) and kappa-casein (CSN3). Measurements were made in cow mammary parenchyma with a prevalence of secretory tissue (MGST). Samples of MGST were collected from the separate quarters and divided into CoPS, CoNS and bacteria-free (H) groups according to the microbiological status of the quarter milk. No differences in CSN1S1 and CSN3 mRNA level were found between groups, however, CSN1S1 protein level was significantly higher in the H group than the CoNS group, and CSN3 protein level was significantly higher in H than CoPS group. Hence, while the CSN1S1 and CSN3 genes appear to be constitutively expressed at the mRNA level in dairy cow MGST during mastitis, CoNS infection negatively affected CSN1S1 protein level, and CoPS infection negatively affected CSN3 protein level. The lack of change at the mRNA level suggests that staphylococcal infection may affect the post-transcriptional or post-translational modifications.

Validation of CSN1S1 transcriptional expression, promoter methylation, and prognostic power in breast cancer using independent datasets

Breast cancer ranked second among most frequent cancer in the world playing a significant role in mortality rate. Having prior knowledge on differentially expressed genes in breast cell carcinoma elucidated important indications to understand the molecular mechanism underneath breast carcinogenesis. In this study we have investigated the distinguished CSN1S1 expression in human breast cancer. We have analyzed CSN1S1 mRNA expression between cancer and normal tissues using TCGA datasets. Moreover, analysis including promoter methylation, mutations, prognosis, co-expression, gene ontology, and pathways of CSN1S1 were performed by the TCGA Wanderer, UCSC Xena, cBioPortal, PrognoScan, UALCAN, and Enricher server. We have observed low mRNA expression and high promoter methylation of CSN1S1 in cancer tissues compared to normal tissues. Furthermore, we have also identified low mRNA expression in clinicopathological patients, as well as 9 deleterious mutations with highly co-expressed protein MRC1, and significantly related signaling pathways. We have found a positive correlation between the lower expression of CSN1S1 and patients surviving with breast cancer. Here we have concluded that CSN1S1 acts as a biomarker for the surveillance and prognosis of breast cancer, and also works as a novel therapeutic target at the molecular and pathway levels.

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Low transcriptional expression and low survival rate of CSN1S1 in breast cancer.

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The investigation of clinical profiles and mutational positions of CSN1S1 in breast cancer.

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The investigation of gene ontology and signaling pathway of CSN1S1 and their co-expressed genes.

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We identified CSN1S1 and also their co-expressed proteins are the potential biomarkers in breast cancer.

Influence of the Casein Composite Genotype on Milk Quality and Coagulation Properties in the Endangered Agerolese Cattle Breed

The aim of this study was the characterization of CSN1S1, CSN2 and CSN3 genetic variability in Agerolese cattle, and the investigation of the effect of casein composite genotypes (CSN1S1, CSN2 and CSN3) on quality and coagulation traits of the corresponding milk. To these purposes, blood and milk from 84 cows were sampled and analysed. Allele frequencies at CSN2 and CSN3 revealed no Hardy-Weinberg equilibrium in the population with a prevalence of allele A² for CSN2 and allele B for CSN3. BBA¹A²AB and BBA²A²AB composite genotypes were the most common in the population. BBA¹A²AB showed a higher total solids and fat content (12.70 ± 0.16 and 3.93 ± 0.10, respectively), while BBA²A²BB showed the best coagulation properties (RCT 12.62 ± 0.81; k₂₀ 5.84 ± 0.37; a₃₀ 23.72 ± 1.10). Interestingly, the A² allele of CSN2 was very widespread in the population; thus, it will be intriguing to verify if A²A² Agerolese cattle milk and the derived cheese may have better nutraceutical characteristics.

Lama glama αS1-casein: Identification of new polymorphisms in the CSN1S1 gene

South American camelids have been poorly genetically investigated and little information is available in llamas (Lama glama) regarding the diversity of the caseins at the protein and gene level. Exon skipping and duplication events previously reported in the α_S1-casein gene (CSN1S1) led us to investigate the genetic variability at this locus. Seventy-two positive clones for the α_S1-casein transcripts were analyzed and randomly sequenced. The comparative analysis of the sequences revealed 2 transitions, c.366A>G and c.690T>C, at the 10th nucleotide of exon 12 and 94 bp of exon 19, respectively. These SNP are responsible for 2 amino acid changes, Ile→Val in position 86 and Tyr→His in position 194 of the mature protein. Both polymorphisms clarify the genetic events behind the protein variants A and B. This result was confirmed by isoelectric focusing analysis of llama milk samples. Quick methods based on PCR-RFLP and allele-specific PCR were set up for allelic discrimination in a population of 128 animals. Based on genotyping results, 4 haplotypes were observed and the estimated frequencies indicated B as the most common haplotype (0.629) in the investigated population. These data add knowledge to the genetic variability of a species little investigated, and open opportunity for new investigation in the field of milk protein for South American camelids, including the possibility, in the future, to select alleles with favorable characteristics.

Comparison of milk oligosaccharides between goats with and without the genetic ability to synthesize αs1-casein

Milk oligosaccharides (OS)-free complex carbohydrates-confer unique health benefits to the nursing neonate. Though human digestive enzymes cannot degrade these sugars, they provide nourishment to specific commensal microbes and act as decoys to prevent the adhesion of pathogenic micro-organisms to gastrointestinal cells. At present, the limited quantities of human milk oligosaccharides (HMO) impede research on these molecules and their potential applications in functional food formulations. Considerable progress has been made in the study of OS structures; however, the synthetic pathways leading to their synthesis in the mammary gland are poorly understood. Recent studies show that complex OS with fucose and N-acetyl neuraminic acid (key structural elements of HMO bioactivity) exist in goat milk. Polymorphisms in the CSN1S1 locus, which is responsible for synthesis of α_s1-casein, affect lipid and casein micelle structure in goat milk. The present study sought to determine whether CSN1S1 polymorphisms also influence goat milk oligosaccharide (GMO) production and secretion. The GMO compositions of thirty-two goat milk samples, half of which were from genotype A/A (α_s1-casein producers) and half from genotype O/O (α_s1-casein non-producers), were determined with nanoflow liquid chromatography high-accuracy mass spectrometry. This study represents the most exhaustive characterization of GMO to date. A systematic and comprehensive GMO library was created, consolidating information available in the literature with the new findings. Nearly 30 GMO, 11 of which were novel, were confirmed via tandem mass spectrometric analyses. Six fucosylated OS were identified; 4 of these matched HMO compositions and three were identified for the first time in goat milk. Importantly, multivariate statistical analysis demonstrated that the OS profiles of the A/A and O/O genotype milks could be discriminated by the fucosylated OS. Quantitative analysis revealed that the goat milk samples contained 1.17 g/L of OS; however, their concentration in milks from A/A and O/O genotypes was not different. This study provides evidence of a genetic influence on specific OS biosynthesis but not total OS production. The presence of fucosylated GMO suggests that goat milk represents a potential source of bioactive milk OS suitable as a functional food ingredient.