title: Complete association between a retroviral insertion in the tyrosinase gene and the recessive white mutation in chickens.
abstract: BACKGROUND
  In chickens, three mutant alleles have been reported at the C locus, including the albino mutation, and the recessive white mutation, which is characterized by white plumage and pigmented eyes. The albino mutation was found to be a 6 bp deletion in the tyrosinase (TYR) gene. The present work describes an approach to identify the structural rearrangement in the TYR gene associated with the recessive white mutation.
  
  
  RESULTS
  Molecular analysis of the chicken TYR gene has revealed a major structural difference (Restriction Fragment Length Polymorphism, RFLP) in the genomic DNA of the recessive white chicken. A major size difference of 7.7 kb was found in intron 4 of the TYR gene by long-range PCR. Molecular cloning and sequencing results showed the insertion of a complete avian retroviral sequence of the Avian Leukosis Virus (ALV) family. Several aberrant transcripts of the tyrosinase gene were found in 10 week old recessive white chickens but not in the homozygous wild type colored chicken. We established a rapid genotyping diagnostic test based on the discovery of this retroviral insertion. It shows that all homozygous carriers of this insertion had a white plumage in various chicken strains. Furthermore, it was possible to distinguish heterozygous carriers from homozygous normal chickens in a segregating line.
  
  
  CONCLUSIONS
  In this study, we conclude that the insertion of a complete avian retroviral sequence in intron 4 of the tyrosinase gene is diagnostic of the recessive white mutation in chickens. This insertion causes aberrant transcripts lacking exon 5, and we propose that this insertion is the causal mutation for the recessive white allele in the chicken.
authors.affiliation: UMR Génétique et Diversité Animales, INRA/INA P-G, Centre de Recherches de Jouy, 78352 Jouy-en-Josas, France. chang@dga2.jouy.inra.fr
authors.forename: Chung-Ming
authors.initials: CM
authors.lastname: Chang
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Coville
authors.forename: Gérard
authors.initials: G
authors.lastname: Coquerelle
authors.forename: David
authors.initials: D
authors.lastname: Gourichon
authors.forename: Ahmad
authors.initials: A
authors.lastname: Oulmouden
authors.forename: Michèle
authors.initials: M
authors.lastname: Tixier-Boichard
mesh_terms: D000818:Animals; D001354:Avian Leukosis Virus / Q000235:genetics*; D001483:Base Sequence; D002645:Chickens / Q000235:genetics* / Q000821:virology*; D004247:DNA / Q000235:genetics; D005091:Exons; D005241:Feathers; D005808:Genes, Recessive; D005838:Genotype; D014442:Monophenol Monooxygenase / Q000235:genetics*; D009154:Mutation; D010858:Pigmentation / Q000235:genetics*; D016133:Polymerase Chain Reaction; D016662:Virus Integration / Q000502:physiology
chemical_list: D004247:DNA; D014442:Monophenol Monooxygenase