title: Bovine chromosomal regions affecting rheological traits in acid-induced skim milk gels.
abstract: The production of fermented milk products has increased worldwide during the last decade and is expected to continue to increase during the coming decade. The quality of these products may be optimized through breeding practices; however, the relations between cow genetics and technological properties of acid milk gels are not fully known. Therefore, the aim of this study was to identify chromosomal regions affecting acid-induced coagulation properties and possible candidate genes. Skim milk samples from 377 Swedish Red cows were rheologically analyzed for acid-induced coagulation properties using low-amplitude oscillation measurements. The resulting traits, including gel strength, coagulation time, and yield stress, were used to conduct a genome-wide association study. Single nucleotide polymorphisms (SNP) were identified using the BovineHD SNPChip (Illumina Inc., San Diego, CA), resulting in almost 621,000 segregating markers. The genome was scanned for putative quantitative trait loci (QTL) regions, haplotypes based on highly associated SNP were inferred, and the additive genetic effects of haplotypes within each QTL region were analyzed using mixed models. A total of 8 genomic regions were identified, with large effects of the significant haplotype explaining between 4.8 and 9.8% of the phenotypic variance of the studied traits. One major QTL was identified to overlap between gel strength and yield stress, the QTL identified with the most significant SNP closest to the gene coding for κ-casein (CSN3). In addition, a chromosome-wide significant region affecting yield stress on BTA 11 was identified to be colocated with PAEP, coding for β-lactoglobulin. Furthermore, the coagulation properties of the genetic variants within the 2 genes were compared with the coagulation properties identified by the patterns of the haplotypes within the regions, and it was discovered that the haplotypes were more diverse and in one case slightly better at explaining the phenotypic variance. Besides these significant QTL comprising the 2 milk proteins, 3 additional genes are proposed as possible candidates, namely RAB22A, CDH13, and STAT1, and all have previously been found to be expressed in the mammary gland. To our knowledge, this is the first attempt to map QTL regions for acid-induced coagulation properties.
authors.affiliation: Department of Food Technology, Engineering and Nutrition, Lund University, PO Box 124, SE-221 00 Lund, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Glantz
authors.affiliation: Department of Food Technology, Engineering and Nutrition, Lund University, PO Box 124, SE-221 00 Lund, Sweden.
authors.forename: F
authors.initials: F
authors.lastname: Gustavsson
authors.affiliation: Department of Molecular Biology and Genetics, Faculty of Science and Technology, Aarhus University, Blichers Allé 20, PO Box 50, DK-8830 Tjele, Denmark.
authors.forename: H P
authors.initials: HP
authors.lastname: Bertelsen
authors.affiliation: VikingGenetics, PO Box 64, SE-532 21 Skara, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Stålhammar
authors.affiliation: Department of Food Technology, Engineering and Nutrition, Lund University, PO Box 124, SE-221 00 Lund, Sweden; Lantbrukarnas Riksförbund Dairy Sweden, Ideon Science Park, SE-223 70 Lund, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Lindmark-Månsson
authors.affiliation: Department of Food Technology, Engineering and Nutrition, Lund University, PO Box 124, SE-221 00 Lund, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Paulsson
authors.affiliation: Department of Molecular Biology and Genetics, Faculty of Science and Technology, Aarhus University, Blichers Allé 20, PO Box 50, DK-8830 Tjele, Denmark.
authors.forename: C
authors.initials: C
authors.lastname: Bendixen
authors.affiliation: Department of Molecular Biology and Genetics, Faculty of Science and Technology, Aarhus University, Blichers Allé 20, PO Box 50, DK-8830 Tjele, Denmark. Electronic address: Vivi.Gregersen@agrsci.dk.
authors.forename: V R
authors.initials: VR
authors.lastname: Gregersen
mesh_terms: D000818:Animals; D001947:Breeding; D002364:Caseins / Q000235:genetics; D002417:Cattle / Q000235:genetics*; D002874:Chromosome Mapping / Q000662:veterinary; D043302:Cultured Milk Products / Q000737:chemistry; D005260:Female; D005782:Gels / Q000737:chemistry*; D014644:Genetic Variation; D055106:Genome-Wide Association Study / Q000662:veterinary; D005838:Genotype; D006239:Haplotypes / Q000235:genetics; D007782:Lactoglobulins / Q000235:genetics; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000378:metabolism; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D040641:Quantitative Trait Loci / Q000235:genetics; D012212:Rheology; D014783:Viscosity
chemical_list: D002364:Caseins; D005782:Gels; D007782:Lactoglobulins; D008894:Milk Proteins
keywords: acid-induced coagulation; dairy cattle; genome-wide association study; milk protein