title: Associations between variants of FADS genes and omega-3 and omega-6 milk fatty acids of Canadian Holstein cows.
abstract: BACKGROUND
  Fatty acid desaturase 1 (FADS1) and 2 (FADS2) genes code respectively for the enzymes delta-5 and delta-6 desaturases which are rate limiting enzymes in the synthesis of polyunsaturated omega-3 and omega-6 fatty acids (FAs). Omega-3 and-6 FAs as well as conjugated linoleic acid (CLA) are present in bovine milk and have demonstrated positive health effects in humans. Studies in humans have shown significant relationships between genetic variants in FADS1 and 2 genes with plasma and tissue concentrations of omega-3 and-6 FAs. The aim of this study was to evaluate the extent of sequence variations within these two genes in Canadian Holstein cows as well as the association between sequence variants and health promoting FAs in milk.
  
  
  RESULTS
  Thirty three SNPs were detected within the studied regions of genes including a synonymous mutation (FADS1-07, rs42187261, 306Tyr > Tyr) in exon 8 of FADS1, a non-synonymous mutation (FADS2-14, rs211580559, 294Ala > Val) within FADS2 exon 7, a splice site SNP (FADS2-05, rs211263660), a 3'UTR SNP (FADS2-23, rs109772589), and another 3'UTR SNP with an effect on a microRNA binding site within FADS2 gene (FADS2-19, rs210169303). Association analyses showed significant relations between three out of seven tested SNPs and several FAs. Significant associations (FDR P < 0.05) were recorded between FADS2-23 (rs109772589) and two omega-6 FAs (dihomogamma linolenic acid [C20:3n6] and arachidonic acid [C20:4n6]), FADS1-07 (rs42187261) and one omega-3 FA (eicosapentaenoic acid, C20:5n3) and tricosanoic acid (C23:0), and one intronic SNP, FADS1-01 (rs136261927) and C20:3n6.
  
  
  CONCLUSIONS
  Our study has demonstrated positive associations between three SNPs within FADS1 and FADS2 genes (a SNP within the 3'UTR, a synonymous SNP and an intronic SNP), with three milk PUFAs of Canadian Holstein cows thus suggesting possible involvement of synonymous and non-coding region variants in FA synthesis. These SNPs may serve as potential genetic markers in breeding programs to increase milk FAs that are of benefit to human health.
authors.affiliation: Dairy and Swine Research and Development Centre, Agriculture and Agri-Food Canada, 2000 Rue College, Sherbrooke, Quebec J1M 0C8, Canada. eveline.ibeagha-awemu@agr.gc.ca.
authors.forename: Eveline M
authors.initials: EM
authors.lastname: Ibeagha-Awemu
authors.forename: Kingsley A
authors.initials: KA
authors.lastname: Akwanji
authors.forename: Frédéric
authors.initials: F
authors.lastname: Beaudoin
authors.forename: Xin
authors.initials: X
authors.lastname: Zhao
mesh_terms: D000818:Animals; D002170:Canada; D002417:Cattle / Q000235:genetics*; D000090943:Delta-5 Fatty Acid Desaturase; D044943:Fatty Acid Desaturases / Q000235:genetics*; D015525:Fatty Acids, Omega-3 / Q000737:chemistry*; D043371:Fatty Acids, Omega-6 / Q000737:chemistry*; D005260:Female; D005838:Genotype; D008892:Milk / Q000737:chemistry*; D020641:Polymorphism, Single Nucleotide; D017422:Sequence Analysis, DNA
chemical_list: D000090943:Delta-5 Fatty Acid Desaturase; D015525:Fatty Acids, Omega-3; D043371:Fatty Acids, Omega-6; D044943:Fatty Acid Desaturases; C000716847:FADS1 protein, human