Allelic heterogeneity of albinism in the domestic cat

Analysis of the genetic loci of pigment pattern evolution in vertebrates

Vertebrate pigmentation patterns are amongst the best characterised model systems for studying the genetic basis of adaptive evolution. The wealth of available data on the genetic basis for pigmentation evolution allows for analysis of trends and quantitative testing of evolutionary hypotheses. We employed Gephebase, a database of genetic variants associated with natural and domesticated trait variation, to examine trends in how cis-regulatory and coding mutations contribute to vertebrate pigmentation phenotypes, as well as factors that favour one mutation type over the other. We found that studies with lower ascertainment bias identified higher proportions of cis-regulatory mutations, and that cis-regulatory mutations were more common amongst animals harbouring a higher number of pigment cell classes. We classified pigmentation traits firstly according to their physiological basis and secondly according to whether they affect colour or pattern, and identified that carotenoid-based pigmentation and variation in pattern boundaries are preferentially associated with cis-regulatory change. We also classified genes according to their developmental, cellular, and molecular functions. We found a greater proportion of cis-regulatory mutations in genes implicated in upstream developmental processes compared to those involved in downstream cellular functions, and that ligands were associated with a higher proportion of cis-regulatory mutations than their respective receptors. Based on these trends, we discuss future directions for research in vertebrate pigmentation evolution.

Donskoy cats as a new model of oculocutaneous albinism with the identification of a splice-site variant in Hermansky-Pudlak Syndrome 5 gene

In the feline Donskoy breed, a phenotype that breeders call "pink-eye," with associated light-brown skin, yellow irises and red-eye effect, has been described. Genealogical data indicated an autosomal recessive inheritance pattern. A single candidate region was identified by genome-wide association study and SNP-based homozygosity mapping. Within that region, we further identified HPS5 (HPS5 Biogenesis Of Lysosomal Organelles Complex 2 Subunit 2) as a strong candidate gene, since HPS5 variants have been identified in humans and animals with Hermansky-Pudlak syndrome 5 or oculocutaneous albinism. A homozygous c.2571-1G>A acceptor splice-site variant located in intron 16 of HPS5 was identified in pink-eye cats. Segregation of the variant was 100% consistent with the inheritance pattern. Genotyping of 170 cats from 19 breeds failed to identify a single carrier in non-Donskoy cats. The c.2571-1G>A variant leads to HPS5 exon-16 splicing that is predicted to produce a 52 amino acids in-frame deletion in the protein. These results support an association of the pink-eye phenotype with the c.2571-1G>A variant. The pink-eye Donskoy cat extends the panel of reported HPS5 variants and offers an opportunity for in-depth exploration of the phenotypic consequences of a new HPS5 variant.

Albinism in Didelphis virginiana (Kerr, 1792): the first reported case in Mexico

Atypical colorations occur in different groups of vertebrates. The loss of melanin in the skin, hair and eyes is the result of an autosomal recessive genetic entity. It causes individuals to present with a white coloration of the skin and hair, as well as red eyes, known as albino. This manuscript documents the first record in Mexico of complete albinism in a marsupial, Didelphis virginiana, captured in the Yucatan peninsula.

Mocha tyrosinase variant: a new flavour of cat coat coloration

A novel coloration named ‘mocha’ has been identified in the Burmese cat breed from Thailand. Tyrosinase (TYR) mutations are known to be associated with coat coloration in cats, such as the sable Burmese, the points of the Siamese and albino cats. Additionally, sable Burmese that produced mocha‐colored cats had unexpected genotypes for TYR. Therefore, TYR was considered a candidate gene for mocha in cats. Sanger sequencing for genomic DNA revealed NC_018732.3:chromosome D1:45 898 609_45 898 771dup in exon 2 and intron 2 of TYR. Transcription analysis using cDNA detected c.820_936delinsAATCTC (p.I274_L312delinsNL), which caused a 111‐bp (37 amino acid) deletion in the reading frame of TYR. The identified variant was concordant with the phenotype and segregated with TYR variants in a pedigree of 12 Burmese cats. This findings of this study suggest that TYR is associated with the mocha coloration in cats. The new color variant adds to the allelic series for TYR (C > c^b = c^s > c, c²) and is recessive to full color (C); however, interactions with the c^b and c^s alleles are unclear due to the temperature‐sensitivity of the alleles.