title: Evaluation of the genetic basis of tricuspid valve dysplasia in Labrador Retrievers.
abstract: OBJECTIVE
  To quantify inheritance of tricuspid valve dysplasia (TVD) in a population of Labrador Retrievers and evaluate the possibility of the effect of a major locus on TVD.
  
  
  METHODS
  521 Labrador Retrievers (345 with known phenotypes and 176 related dogs with unknown phenotypes).
  
  
  METHODS
  Dogs were considered normal, equivocal, and affected for TVD on the basis of echocardiographic appearance of the tricuspid valves. Information on related dogs was collected for estimation of heritability of the 3 categories of phenotype, using a threshold model. Complex segregation analysis was performed to evaluate the possibility of the effect of a major locus on TVD.
  
  
  RESULTS
  Heritability of TVD in this population of dogs was found to be 0.71, a value sufficiently large to suggest a segregating major locus. Subsequent complex segregation analysis did not provide sufficiently strong evidence to indicate influence of a major locus on the prevalence of TVD. However, complex segregation analysis for 2 categories of phenotype (eg, equivocal dogs were grouped with affected dogs) suggested that there was a single recessive allele with a substantial impact on the expression of TVD.
  
  
  CONCLUSIONS
  In Labrador Retrievers, TVD is a heritable disorder. Affected dogs and dogs closely related to affected dogs should not be used for breeding. There was insufficient evidence to suggest the influence of a major locus on TVD, although this conclusion was affected by the classification of dogs for diagnosis of the condition.
authors.affiliation: Department of Animal Science, College of Agricultural and Environmental Sciences, University of California, Davis 95616, USA.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Famula
authors.forename: Lori M
authors.initials: LM
authors.lastname: Siemens
authors.forename: Autumn P
authors.initials: AP
authors.lastname: Davidson
authors.forename: Martin
authors.initials: M
authors.lastname: Packard
mesh_terms: D000483:Alleles; D000818:Animals; D001499:Bayes Theorem; D001947:Breeding / Q000592:standards; D004283:Dog Diseases / Q000235:genetics*; D004285:Dogs; D005260:Female; D008297:Male; D010375:Pedigree; D010641:Phenotype; D014262:Tricuspid Valve Insufficiency / Q000175:diagnosis / Q000235:genetics / Q000662:veterinary*