Glantz M, Gustavsson F, Bertelsen H P, Stålhammar H, Lindmark-Månsson H, Paulsson M, Bendixen C, Gregersen V R
Department of Food Technology, Engineering and Nutrition, Lund University, PO Box 124, SE-221 00 Lund, Sweden.
Department of Molecular Biology and Genetics, Faculty of Science and Technology, Aarhus University, Blichers Allé 20, PO Box 50, DK-8830 Tjele, Denmark.
J Dairy Sci. 2015 Feb;98(2):1273-85. doi: 10.3168/jds.2014-8137. Epub 2014 Dec 18.
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.
在过去十年中，全球发酵乳制品的产量有所增加，预计在未来十年还将继续增长。这些产品的质量可通过育种实践加以优化；然而，奶牛遗传学与酸牛奶凝胶技术特性之间的关系尚未完全明晰。因此，本研究的目的是确定影响酸诱导凝固特性的染色体区域以及可能的候选基因。对377头瑞典红牛的脱脂乳样品进行了流变学分析，采用低振幅振荡测量法测定酸诱导凝固特性。将所得性状，包括凝胶强度、凝固时间和屈服应力，用于全基因组关联研究。使用牛HD SNP芯片（Illumina公司，加利福尼亚州圣地亚哥）鉴定单核苷酸多态性（SNP），产生了近621,000个分离标记。扫描基因组以寻找假定的数量性状位点（QTL）区域，推断基于高度相关SNP的单倍型，并使用混合模型分析每个QTL区域内单倍型的加性遗传效应。共鉴定出8个基因组区域，显著单倍型的较大效应解释了所研究性状表型变异的4.8%至9.8%。一个主要QTL被确定在凝胶强度和屈服应力之间重叠，该QTL与编码κ-酪蛋白（CSN3）的基因最接近的最显著SNP所鉴定。此外，在BTA 11上影响屈服应力的全染色体显著区域被确定与编码β-乳球蛋白的PAEP共定位。此外，比较了这两个基因内遗传变异的凝固特性与区域内单倍型模式所鉴定的凝固特性，发现单倍型更多样化，且在一种情况下能更好地解释表型变异。除了包含这两种乳蛋白的这些显著QTL外，还提出了另外3个基因作为可能的候选基因，即RAB22A、CDH13和STAT1，并且之前均已发现它们在乳腺中表达。据我们所知，这是首次绘制酸诱导凝固特性QTL区域的尝试。
