title: Refined mapping of twinning-rate quantitative trait loci on bovine chromosome 5 and analysis of insulin-like growth factor-1 as a positional candidate gene.
abstract: Twinning in cattle is a complex trait that is associated with economic loss and health issues such as abortion, dystocia, and reduced calf survival. Twinning-rate QTL have been detected previously on BTA5 in the North American Holstein and Norwegian dairy cattle populations and in a USDA herd selected for high twinning rate. In previous work with the North American Holstein population, the strongest evidence for a QTL was obtained from analysis of an extended, multiple-generation family. Using additional animals, an increased density of SNP marker association tests, and a combined linkage and linkage disequilibrium mapping method, we refined the position of this QTL in the North American Holstein population. Two sets of twinning-rate predicted transmitting abilities estimated during 2 different time periods in the North American dairy cattle population were used to provide validation of results. A total of 106 SNP and 3 microsatellites were used to scan the genomic region between 5 and 80 Mb on BTA5. Combined linkage-linkage disequilibrium analysis identified significant evidence for QTL within the 25- to 35-Mb and 64- to 70-Mb regions of BTA5. The IGF-1 gene (IGF1) was examined as a positional candidate gene and an SNP in intron 2 of IGF1 was significantly associated with twinning rate by using both data sets (P = 0.003 and P = 1.05 x 10(-6)). Replication of this association in other cattle populations will be required to examine the extent of linkage disequilibrium with the underlying quantitative trait nucleotide across breeds.
authors.affiliation: Department of Animal Sciences, University of Wisconsin, Madison 53706, USA.
authors.forename: E-S
authors.initials: ES
authors.lastname: Kim
authors.forename: X
authors.initials: X
authors.lastname: Shi
authors.forename: O
authors.initials: O
authors.lastname: Cobanoglu
authors.forename: K
authors.initials: K
authors.lastname: Weigel
authors.forename: P J
authors.initials: PJ
authors.lastname: Berger
authors.forename: B W
authors.initials: BW
authors.lastname: Kirkpatrick
mesh_terms: D000818:Animals; D002417:Cattle / Q000235:genetics*; D002874:Chromosome Mapping; D033481:Chromosomes, Mammalian / Q000235:genetics*; D005260:Female; D005819:Genetic Markers; D006239:Haplotypes; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D015810:Linkage Disequilibrium; D008297:Male; D020641:Polymorphism, Single Nucleotide; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000235:genetics*; D040641:Quantitative Trait Loci / Q000235:genetics*
chemical_list: D005819:Genetic Markers; D007334:Insulin-Like Growth Factor I