title: Bovine chromosomal regions affecting rheological traits in rennet-induced skim milk gels.
abstract: Optimizing cheese yield and quality is of central importance to cheese manufacturing. The yield is associated with the time it takes before the gel has an optimal consistency for further processing, and it is well known that gel formation differs between individual milk samples. By identifying genomic regions affecting traits related to rennet-induced gelation, the aim of this study was to identify potential candidate genes affecting these traits. Hence, rennet-induced gelation, including rennet coagulation time, gel strength, and yield stress, was measured in skim milk samples collected from 379 animals of the Swedish Red breed using low-amplitude oscillation measurements. All animals had genotypes for almost 621,000 segregating single nucleotide polymorphisms (SNP), identified using the Bovine HD SNPChip (Illumina Inc., San Diego, CA). The genome was scanned for associations, haplotypes based on SNP sets comprising highly associated SNP were inferred, and the effects of the 2 most common haplotypes within each region were analyzed using mixed models. Even though the number of animals was relatively small, a total of 21 regions were identified, with 4 regions showing association with more than one trait. A major quantitative trait locus for all traits was identified around the casein cluster explaining between 9.3 to 15.2% of the phenotypic variation of the different traits. In addition, 3 other possible candidate genes were identified; that is, UDP-N-acetyl-α-d-galactosamine:polypeptide N-acetylgalactosaminyl-transferase 1 (GALNT1), playing a role in O-glycosylation of κ-casein, and 2 cathepsins, CTSZ and CTSC, possibly involved in proteolysis of milk proteins. We have shown that other genes than the casein genes themselves may be involved in the regulation of gelation traits. However, additional analysis is needed to confirm these results. To our knowledge, this is the first study identifying quantitative trait loci affecting rennet-induced gelation of skim milk through a high-density genome-wide association study.
authors.affiliation: Department of Molecular Biology and Genetics, Faculty of Science and Technology, Aarhus University, Blichers Allé 20, PO Box 50, 8830 Tjele, Denmark. Electronic address: Vivi.Gregersen@agrsci.dk.
authors.forename: V R
authors.initials: VR
authors.lastname: Gregersen
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 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 Molecular Biology and Genetics, Faculty of Science and Technology, Aarhus University, Blichers Allé 20, PO Box 50, 8830 Tjele, Denmark.
authors.forename: O F
authors.initials: OF
authors.lastname: Christensen
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 Science, BioCenter, Swedish University of Agricultural Sciences, Box 7051, SE-750 07 Uppsala, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Andrén
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 Science, Faculty of Science and Technology, Aarhus University, Blichers allé 20, PO Box 50, 8830 Tjele, Denmark.
authors.forename: N A
authors.initials: NA
authors.lastname: Poulsen
authors.affiliation: Department of Food Science, Faculty of Science and Technology, Aarhus University, Blichers allé 20, PO Box 50, 8830 Tjele, Denmark.
authors.forename: L B
authors.initials: LB
authors.lastname: Larsen
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, 8830 Tjele, Denmark.
authors.forename: C
authors.initials: C
authors.lastname: Bendixen
mesh_terms: D000818:Animals; D001947:Breeding; D002364:Caseins / Q000235:genetics; D002417:Cattle / Q000235:genetics*; D002611:Cheese; D055598:Chemical Phenomena; D002874:Chromosome Mapping / Q000662:veterinary; D012085:Chymosin; D005260:Female; D005782:Gels / Q000737:chemistry*; D016678:Genome; D055106:Genome-Wide Association Study; D005838:Genotype; D006239:Haplotypes / Q000235:genetics; D007782:Lactoglobulins / Q000235:genetics; D008892:Milk / Q000737:chemistry* / Q000378:metabolism; D008894:Milk Proteins / Q000378:metabolism; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D040641:Quantitative Trait Loci / Q000235:genetics; D015203:Reproducibility of Results; D012212:Rheology; D014783:Viscosity
chemical_list: D002364:Caseins; D005782:Gels; D007782:Lactoglobulins; D008894:Milk Proteins; C025350:rennet; D012085:Chymosin
keywords: casein; dairy cattle; genome-wide association study; milk gelation