In other species: domestic cat , cattle , dog , rabbit , water buffalo , ass , Japanese medaka , humpback whale , domestic ferret , pig , domestic guinea pig , Tufted capuchin , dark-spotted frog , Japanese wrinkled frog , Rice frog , lion , Mongolian gerbil , red fox , hamadryas baboon , red deer , Japanese raccoon dog , Japanese ratsnake , , golden hamster

Categories: Pigmentation phene

Possibly relevant human trait(s) and/or gene(s)s (MIM numbers): 203100 (trait) , 606952 (trait) , 606933 (gene)

Links to MONDO diseases: No links.

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal recessive

Considered a defect: yes

Key variant known: yes

Year key variant first reported: 2008

Cross-species summary: Congenital lack of pigment in most parts of the body. Due to a non-functional form of the enzyme tyrosinase. Also known as Oculocutaneous albinism (OCA), Acromelanism and as the Himalayan coat-colour pattern

Species-specific description: Two mutant alleles have been characterized at the molecular level: albino (complete loss of function) and marbled or Himalayan (temperature-sensitive partial loss of function). The Himalayan phenotype is similar to that of the Siamese and Burmese cats: "light-colored body with dark-colored points (ears, face, tail, and feet)" (Benkel et al., 2009).

Inheritance: The predicted dominance hierarchy is: wildtype > Himalayan > albino

Mapping: Anistoroaei et al. (2008) linkage-mapped the albino locus in American mink to two microsatellites known to be located in the region of the mink genome homologous to the TYR gene in other species. They also physically mapped a BAC clone containing one of the two linked microsatellites (Mvi6034) "to chromosome 7q1.1-q1.3 by fluorescent in situ hybridization".

Molecular basis: By sequencing the strong comparative positional (see Mapping section) and functional candidate gene (TYR), Anistoroaei et al. (2008) showed that albinism in American Mink is due to "a nonsense mutation in exon 1, which converts a TGT codon encoding cysteine to a TGA stop codon (c.138T>A, p.C46X; EU627590). The mutation truncates more than 90% of the normal gene product including the putative catalytic domains."

By sequencing a very strong comparative and functional candidate gene, Benkel et al (2009) showed that "marbled mink carry a mutation in exon 4 of the TYR gene (c.1835C > G) which results in an amino acid substitution (p.H420Q). The location of this substitution corresponds to the amino acid position that is also mutated in the TYR protein of the Himalayan mouse. Thus, the marbled variant is more aptly referred to as the Himalayan mink."

Associated gene: