The Tabby cat locus maps to feline chromosome B1

Abstract

The Tabby markings of the domestic cat are unique coat patterns for which no causative candidate gene has been inferred from other mammals. In this study, a genome scan was performed on a large pedigree of cats that segregated for Tabby coat markings, specifically for the Abyssinian (Ta-) and blotched (tbtb) phenotypes. There was linkage between the Tabby locus and eight markers on cat chromosome B1. The most significant linkage was between marker FCA700 and Tabby (Z = 7.56, theta = 0.03). Two additional markers in the region supported linkage, although not with significant LOD scores. Pairwise analysis of the markers supported the published genetic map of the cat, although additional meioses are required to refine the region. The linked markers cover a 17-cM region and flank an evolutionary breakpoint, suggesting that the Tabby gene has a homologue on either human chromosome 4 or 8. Alternatively, Tabby could be a unique locus in cats.

Figure 1

Tabby patterns in the domestic shorthair cats: (a) Abysinnian, T^a-, (b) mackerel, T^mT^m or Tt^b, and (c) blotched, t^bt^b. The Abysinnian pattern is also known as ticked, the mackerel pattern as striped and the blotched pattern as classic. Homozygous T^aT^a individuals have the same pattern on the torso but may have less barring on the legs and tail. The T^mt^bmackerel pattern may appear as the broken mackerel or spotted mackerel patterns; however, these phenotypes have not segregated in pedigrees, and the spotted pattern may be affected by modifiers.

Figure 2

Pedigree segregating for domestic cat Tabby patterns and linked markers from cat chromosome B1. Circles represent females, squares represent males, filled symbols indicate phenotypically Tabby Abyssinian cats, symbols with a center dot are Tabby blotched patterned cats and striped symbols indicate Tabby mackerel pattern cats. Unknown patterns are presented as open symbols. Unknown cats had solid, non-agouti colours, thus Tabby patterns could not be distinguished. Symbols with a diagonal slash represent cats that were not available for the analyses. Numbers under the symbols represent the laboratory sample numbers. Genotypes for the seven linked markers (FCA023, FCA809, FCA811, FCA812, FCA700, FCA254 and FCA813) are represented below the cat identification numbers respectively and are presented as haplotypes. No genotype data are represented by ‘0’. Cat H118 was duplicated to break an inbreeding loop and is also represented as B118. Cats that are recombinants between at least one marker in the haplotype and the Tabby phenotype are indicated with an ‘R’.