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, 37 (2), 175-8

Albinism in the Domestic Cat (Felis Catus) Is Associated With a Tyrosinase (TYR) Mutation

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Albinism in the Domestic Cat (Felis Catus) Is Associated With a Tyrosinase (TYR) Mutation

D L Imes et al. Anim Genet.

Abstract

Albino phenotypes are documented in a variety of species including the domestic cat. As albino phenotypes in other species are associated with tyrosinase (TYR) mutations, TYR was proposed as a candidate gene for albinism in cats. An Oriental and Colourpoint Shorthair cat pedigree segregating for albinism was analysed for association with TYR by linkage and sequence analyses. Microsatellite FCA931, which is closely linked to TYR and TYR sequence variants were tested for segregation with the albinism phenotype. Sequence analysis of genomic DNA from wild-type and albino cats identified a cytosine deletion in TYR at position 975 in exon 2, which causes a frame shift resulting in a premature stop codon nine residues downstream from the mutation. The deletion mutation in TYR and an allele of FCA931 segregated concordantly with the albino phenotype. Taken together, our results suggest that the TYR gene corresponds to the colour locus in cats and its alleles, from dominant to recessive, are as follows: C (full colour) > c(b) (burmese) > or = c(s) (siamese) > c (albino).

Figures

Figure 1
Figure 1
Pedigree segregating for complete and temperature-sensitive albinism (siamese, cs) in Colourpoint Shorthair cats. Circles represent females, squares represent males, solid symbols indicate phenotypically siamese-coloured (cscs or csc) cats and clear symbols indicate albino cats. Diamonds represent individuals with unknown gender, a slash through a symbol implies the individual was stillborn. Small filled circles represent ‘breeding nodes’ for parental cats. Numbers under the symbols represent laboratory sample numbers. Samples from cats 1–17 were not available for testing. Genotypes for the C deletion at position 975 in exon 2 are presented below the laboratory numbers. A ‘+’ indicates the normal wild-type sequence and ‘−’ indicates the C deletion. Genotypes for the linked microsatellite marker FCA931 are represented below the mutation genotypes. The base-pair sizes of the microsatellite markers were converted to single numbers to distinguish the alleles. Missing data are represented by ‘0’. An ‘R’ indicates the detectable recombination event in individual 4900.
Figure 2
Figure 2
Phenotypes in a domestic cat pedigree (Fig. 1) that segregated for albinism: (a) albino, (b) a Colourpoint (chocolate lynx-point non-albino) sibling ; and c) a litter of kittens that includes an albino (third from the left).
Figure 3
Figure 3
Exon 2 nucleotide and protein sequence alignments of feline and human tyrosinase (TYR). The TYR nucleotide sequences for Felis catus (FCA) and Homo sapiens (HSA) were AY743347 and M27160 respectively. The amino acids (aa's) for each codon are listed below the nucleotide sequences. The albino mutation is a cytosine deletion at nucleotide 975 that causes a frameshift, leading to a stop (OCH) codon nine residues downstream of the deletion GenBank accession no. AY743347. The portion of the cat albino allele that is altered relative to the wild-type sequence is presented in bold. Amino acids that are conserved among dogs, human, mice and cattle are underlined. The rabbit has a single amino acid change in this region, replacing an alanine with a serine.

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