ABSTRACT
The aim of this study was to more precisely map a previously reported quantitative trait locus (QTL) affecting somatic cell score on Bos taurus autosome 2 by increasing the number of markers fourfold, analysing more families and exploiting within-population linkage disequilibrium (LD). A granddaughter design of 10 German Holstein grandsire families with 1121 progeny tested sons was used. Twenty-six markers with an average marker spacing of 3.14 cM were genotyped along 81.6 cM. Linkage analysis (LA) was performed using variance-component methodology. The incorporation of LD was first done using variance-component methods followed by regression on marker alleles. LA revealed genome-wide significance (LOD > 3) at 15 contiguous marker-intervals, with the maximum test-statistic between DIK2862 and BMS778 and a 1-lod drop-off interval of 38 cM. While the variance-component methods could not detect any LD, two individual markers with a significant effect (ILSTS098, p < 0.05; BMS778, p < 0.01) were found by regression analysis. Compared with previous results QTL-localisation was substantially narrowed; further fine-mapping should focus on the close vicinity of BMS778.
Subject(s)
Body Constitution/genetics , Breeding/methods , Cattle/genetics , Chromosome Mapping , Chromosomes, Mammalian/genetics , Dairying/methods , Quantitative Trait Loci/genetics , Animals , Genetic Markers/genetics , Germany , Linkage Disequilibrium , Regression AnalysisABSTRACT
In addition to its position in a quantitative trait locus for somatic cell score (SCS) and its function in the immune response, the CXCR1 chemokine receptor gene located on Bos taurus autosome 2 is an auspicious candidate gene for udder health in dairy cattle. An association analysis was conducted in the German Holstein-Friesian population to test the association between the single nucleotide polymorphism (SNP) at position +777 within the CXCR1 gene and the SNP at position -1768 in the 5' upstream region of this gene (rs41255711) and the indicator trait SCS by using a grand-daughter design. Data were analyzed for 3 families, with a total of 749 genotyped bulls and an extended pedigree of 8,071 animals from the national German bovine genome mapping project. Variance component estimation was used to determine the source of phenotypic variation in the chromosomal area of interest. A 20-cM window surrounding the 2 SNP in the CXCR1 gene was examined. Although the percentage of variance caused by the putative quantitative trait locus in the area studied was relatively large (12 and 11%, respectively), no statistically significant association of the SNP CXCR1+777 or CXCR1-1768 with SCS was found. These results contradict previously published studies.
