Identification of a candidate genetic variant for the Himalayan color pattern in dogs

Acromelanism is a temperature-dependent hypopigmentation pattern commonly manifested as the Himalayan coat color found in rabbits, rats, mice, minks, and gerbils, wherein the extreme "points" are dark and the torso is pale. It is known as the Siamese pattern in cats. Himalayan color is genetically determined by the allelic variant c^h of the locus C, later identified as the tyrosinase gene TYR. The tyrosinase functions at the initial steps of melanin production, and alteration of its activity by sequence changes results in pigmentation defects in vertebrates. The presence of acromelanism in dogs has not been described until now. We analyzed a DNA sample of a dachshund with a unique coat color resembling the Himalayan type. Sequencing of the coding part of the TYR gene from the proband revealed a homozygous variant (c.230G > A) in exon 1, leading to an amino acid substitution (p.R77Q) in a conserved region of the protein. The proband's mother, which is black-and-tan, is a heterozygous carrier of the c.230A allele, while none of the 210 dogs of different breeds, unrelated to the proband, carried the c.230A allele. These results suggest that the identified sequence variant is likely the cause of the Himalayan coloration of the proband.

A genetic typing method for albino mutation in the Mongolian gerbil by PCR-RFLP analysis

1. We established a PCR-RFLP analysis targeting R77H mutation in the Tyr gene as a more effective genotyping to identify carrier (C/c) with the albino allele and the agouti phenotypes. 2. Our breeding system, which targets the R77H site, is a useful cue for detecting C/c carriers with the agouti-phenotype and helps us to obtain albinos by mating agouti-phenotype carriers.