A Novel SNPs in Alpha-Lactalbumin Gene Effects on Lactation Traits in Chinese Holstein Dairy Cows

Abstract

Simple Summary: Alpha-lactalbumin (α-LA) is a major whey protein component in mammalian milk, such as human (approximately 36%), bovine (approximately 17%), and other species, etc., It is involved in the regulation of lactose synthesis and has high nutritional value, especially in infant formula. Previous studies have confirmed that bovine α-LA gene 5 -flanking region has single nucleotide polymorphisms (SNPs), but little is known about polymorphisms in other regions, especially sequence coding for amino acids in protein (CDS) and their adjacent non-coding regions, including Chinese Holstein dairy cows. This study focused on investigated SNPs in the CDS and their adjacent non-coding regions of the α-LA gene in Chinese Holstein dairy cows, and assessed the association between SNPs and lactation traits. Sequence alignment showed that a potential SNPs (562th, G/A) in CDS2 region affect protein spatial structure, suggesting that this SNPs might affect the lactation traits of cows (milk type (Holstein and Jersey), and non-milk type (Bos Taurus)) need more in-depth study. More importantly, a novel SNPs at 1847th (T/C) bp in non-coding region near CDS4 was significantly associated with milk lactose composition, and lactose contents were significantly correlated with milk protein content, indicating that the SNPs could be used as a novel potential molecular marker for lactation traits in Chinese Holstein dairy cows.Abstract: Alpha-lactalbumin (α-LA) is a major whey protein in bovine and other mammalian milk, which regulates synthesis of lactose. Little is known about its genetic polymorphism and whether can be used as a potential marker for dairy ingredients, milk yield traits, and milk properties. To investigate its polymorphisms and their relationship with milk lactation traits in Chinese Holstein dairy cows, single-strand conformation polymorphism method (PCR-SSCP) and direct sequencing method were used to mark the α-LA gene SNPs. AA (0.7402) and AB (0.2598) genotypes were screened out by PCR-SSCP bands analysis in two independent populations. Direct sequencing revealed that there is one SNP at 1847th (T/C) bp in noncoding region of α-LA gene with highly polymorphic (0.5 < PIC = 0.5623 or 0.5822), of which T is in AA genotype while C in AB. Association analysis also showed that lactose content (p < 0.05) was negatively correlated with fat and protein contents within subgroup, indicating that the SNPs (1847th, T/C) in α-LA gene could be used as a novel potential molecular marker for lactation traits in Chinese Holstein dairy cows.

Genomewide Association Analyses of Lactation Persistency and Milk Production Traits in Holstein Cattle Based on Imputed Whole-Genome Sequence Data

“…The terms GO:1903496 and GO:1903494 were also found for PROT, reinforcing the relevance of the casein gene cluster for milk protein, in both forms, total yield and percentage. Additionally, in both terms, the gene LALBA (milk whey protein α-lactoalbumin) was also identified for PROT%, highlighting the involvement of this well-known gene with PROT%, as previously reported in other dairy cattle studies [111,112]. On GO:0007595, many genes known for its association with PROT% were identified such as STAT5A, STAT5B, ATP2B2, CSN3, CSN2, and PRLR, validating the connection of these genes with milk composition in dairy cattle.…”

A Comparative Review of the Extrinsic and Intrinsic Factors Regulating Lactose Synthesis

“…In a similar way, an I/V substitution at amino acid 46, the site of LALBA glycosylation, did not affect LALBA or lactose concentration in human milk [170], and none of four SNP in the 5'UTR of the equine LALBA mRNA were associated with altered LALBA mRNA or protein expression [177]. Among Chinese Holstein dairy cows, a T1847C SNP in a noncoding region was associated with lower lactose content and yield, but not fat or protein content [180]. Nine SNP were identified in the 5'UTR and 3'UTR of the Sarda goat LALBA mRNA transcripts, of which two SNP (-368 and -163) located at apetala 2α and specific factor 1 transcription factor binding sites, respectively, were associated with lower milk lactose content [181].…”

Diversity of Mitochondrial DNA Haplogroups and Their Association with Bovine Antral Follicle Count

“…These studies also indicated that genetic resources were abundant and needed to be further examined in Chinese Holstein cows. Furthermore, more extensive research on polymorphisms within specific genes revealed that they correlated with milk production traits and reproduction traits in Chinese Holstein cows [ 42 , 43 , 44 , 45 ]. In particular, in studies on mutations within mitochondrial genes [ 36 , 46 , 47 , 48 , 49 ], the association of mtDNA genetic diversity with reproductive traits or environmental adaptation to high altitudes in cattle or yaks was also revealed.…”