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1.  An Insertion in the RSPO2 Gene Correlates with Improper Coat in the Portuguese Water Dog 
Journal of Heredity  2010;101(5):612-617.
We recently showed that genes at 3 loci account for the majority of variation in canine fur. Allelic variation at genes controlling length of fur, texture, and curl is responsible for the striking phenotypic variety observed among purebred dogs in the United States today. In this paper, we investigate the phenomenon of “improper coat” (IC) or a coat that is not typical of the breed. IC is occasionally observed among specific breeds, such as the Portuguese Water Dog (PWD), and is characterized by short hair on the head, face, and lower legs, rather than a thick and even coat covering the whole body. The IC is reminiscent of that observed on the curly or flat-coated retriever, thus making such dogs unable to compete effectively in conformation events. We have found that the presence of the wild-type allele, rather than the expected variant allele at the R-spondin 2 (RSPO2) gene, accounts for this phenotype. The development of a genetic test that distinguishes these 2 allelic types would allow breeders to easily avoid producing PWD with ICs.
doi:10.1093/jhered/esq068
PMCID: PMC2908740  PMID: 20562213
fur; furnishings; genetics; morphology; mutation
2.  Coat Variation in the Domestic Dog Is Governed by Variants in Three Genes 
Science (New York, N.Y.)  2009;326(5949):150-153.
Coat color and type are essential characteristics of domestic dog breeds. Although the genetic basis of coat color has been well characterized, relatively little is known about the genes influencing coat growth pattern, length, and curl. We performed genome-wide association studies of more than 1000 dogs from 80 domestic breeds to identify genes associated with canine fur phenotypes. Taking advantage of both inter- and intrabreed variability, we identified distinct mutations in three genes, RSPO2, FGF5, and KRT71 (encoding R-spondin–2, fibroblast growth factor–5, and keratin-71, respectively), that together account for most coat phenotypes in purebred dogs in the United States. Thus, an array of varied and seemingly complex phenotypes can be reduced to the combinatorial effects of only a few genes.
doi:10.1126/science.1177808
PMCID: PMC2897713  PMID: 19713490
3.  Genetic Mapping of Fixed Phenotypes: Disease Frequency as a Breed Characteristic 
Journal of Heredity  2009;100(Suppl 1):S37-S41.
Traits that have been stringently selected to conform to specific criteria in a closed population are phenotypic stereotypes. In dogs, Canis familiaris, such stereotypes have been produced by breeding for conformation, performance (behaviors), etc. We measured phenotypes on a representative sample to establish breed stereotypes. DNA samples from 147 dog breeds were used to characterize single nucleotide polymorphism allele frequencies for association mapping of breed stereotypes. We identified significant size loci (quantitative trait loci [QTLs]), implicating candidate genes appropriate to regulation of size (e.g., IGF1, IGF2BP2 SMAD2, etc.). Analysis of other morphological stereotypes, also under extreme selection, identified many additional significant loci. Behavioral loci for herding, pointing, and boldness implicated candidate genes appropriate to behavior (e.g., MC2R, DRD1, and PCDH9). Significant loci for longevity, a breed characteristic inversely correlated with breed size, were identified. The power of this approach to identify loci regulating the incidence of specific polygenic diseases is demonstrated by the association of a specific IGF1 haplotype with hip dysplasia, patella luxation, and pacreatitis.
doi:10.1093/jhered/esp011
PMCID: PMC3139361  PMID: 19321632
association; canine; disease; longevity; morphology; QTL
4.  A Single IGF1 Allele Is a Major Determinant of Small Size in Dogs 
Science (New York, N.Y.)  2007;316(5821):112-115.
The domestic dog exhibits greater diversity in body size than any other terrestrial vertebrate. We used a strategy that exploits the breed structure of dogs to investigate the genetic basis of size. First, through a genome-wide scan, we identified a major quantitative trait locus (QTL) on chromosome 15 influencing size variation within a single breed. Second, we examined genetic variation in the 15-megabase interval surrounding the QTL in small and giant breeds and found marked evidence for a selective sweep spanning a single gene (IGF1), encoding insulin-like growth factor 1. A single IGF1 single-nucleotide polymorphism haplotype is common to all small breeds and nearly absent from giant breeds, suggesting that the same causal sequence variant is a major contributor to body size in all small dogs.
doi:10.1126/science.1137045
PMCID: PMC2789551  PMID: 17412960
5.  Bilaterally Asymmetric Effects of Quantitative Trait Loci (QTLs): QTLs That Affect Laxity in the Right Versus Left Coxofemoral (Hip) Joints of the Dog (Canis familiaris) 
In dogs hip joint laxity that can lead to degenerative joint disease (DJD) is frequent and heritable, providing a genetic model for some aspects of the human disease. We have used Portuguese water dogs (PWDs) to identify Quantitative trait loci (QTLs) that regulate laxity in the hip joint.A population of 286 PWDs, each characterized by ca. 500 molecular genetic markers, was analyzed for subluxation of the hip joint as measured by the Norberg angle, a quantitative radiographic measure of laxity. A significant directed asymmetry was observed, such that greater laxity was observed in the left than the right hip. This asymmetry was not heritable. However, the average Norberg angle was highly heritable as were the Norberg angles of either the right or left hips. After correction for pedigree effects, two QTLs were identified using the metrics of the left and right hips as separate data sets. Both are on canine chromosome 1 (CFA1), separated by about 95 Mb. One QTL, associated with the SSR marker FH2524 was significant for the left, but not the right hip. The other, associated with FH2598, was significant for the right but not the left hip. For both QTLs, some extreme phenotypes were best explained by specific interactions between haplotypes.
doi:10.1002/ajmg.a.20363
PMCID: PMC2778498  PMID: 14708095
quantitative trait loci (QTLs); dog; hip laxity; bilateral asymmetry; Norberg angle; Canine genetics; hip dysplasia

Results 1-5 (5)