Alexandra E. Ankersmit-Udy

Fonterra (New Zealand)

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Mutation in Bovine β-Carotene Oxygenase 2 Affects Milk Color

Genetics (2009)

Sarah Berry Stephen R. Davis E M Beattie Natalie Thomas Alayna Burrett

beta-Carotene biochemistry is a fundamental process in mammalian biology. Aberrations either through malnutrition or potentially through genetic variation may lead to vitamin A deficiency, which is a substantial public health burden. In addition, understanding the genetic regulation of this process may enable bovine improvement. While many bovine QTL have been reported, few of the causative genes and mutations have been identified. We discovered a QTL for milk beta-carotene and subsequently identified a premature stop codon in bovine beta-carotene oxygenase 2 (BCO2), which also affects serum beta-carotene content. The BCO2 enzyme is thereby identified as a key regulator of beta-carotene metabolism.

Carotene

10.1534/genetics.109.101741

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Citations (94)

Screening for phenotypic outliers identifies an unusually low concentration of a β-lactoglobulin B protein isoform in bovine milk caused by a synonymous SNP

Genetics Selection Evolution (2022)

Stephen R. Davis Hamish E. Ward Van Kelly David J. Palmer Alexandra E. Ankersmit-Udy

Milk samples from 10,641 dairy cattle were screened by a mass spectrometry method for extreme concentrations of the A or B isoforms of the whey protein, β-lactoglobulin (BLG), to identify causative genetic variation driving changes in BLG concentration.A cohort of cows, from a single sire family, was identified that produced milk containing a low concentration of the BLG B protein isoform. A genome-wide association study (GWAS) of BLG B protein isoform concentration in milk from AB heterozygous cows, detected a group of highly significant single nucleotide polymorphisms (SNPs) within or close to the BLG gene. Among these was a synonymous G/A variation at position + 78 bp in exon 1 of the BLG gene (chr11:103256256G > A). The effect of the A allele of this SNP (which we named B') on BLG expression was evaluated in a luciferase reporter assay in transfected CHO-K1 and MCF-7 cells. In both cell types, the presence of the B' allele in a plasmid containing the bovine BLG gene from -922 to + 898 bp (relative to the transcription initiation site) resulted in a 60% relative reduction in mRNA expression, compared to the plasmid containing the wild-type B sequence allele. Examination of a mammary RNAseq dataset (n = 391) identified 14 heterozygous carriers of the B' allele which were homozygous for the BLG B protein isoform (BB'). The level of expression of the BLG B' allele was 41.9 ± 1.0% of that of the wild-type BLG B allele. Milk samples from three cows, homozygous for the A allele at chr11:103,256,256 (B'B'), were analysed (HPLC) and showed BLG concentrations of 1.04, 1.26 and 1.83 g/L relative to a mean of 4.84 g/L in milk from 16 herd contemporaries of mixed (A and B) BLG genotypes. The mechanism by which B' downregulates milk BLG concentration remains to be determined.High-throughput screening and identification of outliers, enabled the discovery of a synonymous G > A mutation in exon 1 of the B allele of the BLG gene (B'), which reduced the milk concentration of β-lactoglobulin B protein isoform, by more than 50%. Milk from cows carrying the B' allele is expected to have improved processing characteristics, particularly for cheese-making.

10.1186/s12711-022-00711-z

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Citations (8)

Additional file 2 of Screening for phenotypic outliers identifies an unusually low concentration of a β-lactoglobulin B protein isoform in bovine milk caused by a synonymous SNP

Figshare (2022)

Stephen R. Davis Hamish E. Ward Van Kelly David J. Palmer Alexandra E. Ankersmit-Udy

Additional file 2: Table S1. GWAS results for the top 250 SNPs in the region of the BLG gene that were associated with total BLG concentration in milk (n = 4140). Two SNPs that differentiate the A and B protein isoforms are highlighted. Table S2. GWAS results for the top 250 SNPs in the region of the BLG gene that were associated with BLG B isoform concentrations in milks from heterozygous AB animals (n = 1966). The top SNP (highlighted) is B’ (chr11: 103256256G > A).

SNP

Bovine milk

Beta-lactoglobulin

10.6084/m9.figshare.19373421

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Citations (0)