Deafness (associated with Dominant White) (W Locus)

 

Gene:  KIT

Transmission: Autosomal, dominant (complete penetrance for whiteness, incomplete penetrance for deafness)

For a genetic disease that is autosomal dominant, the animal only has to have one copy of the mutation to be at risk of developing hypertrophic cardiomyopathy.  Animals with two copies of the mutation generally have more severe symptoms and an earlier onset of the disease than animals with just one copy of the mutation.  Offspring are potentially at risk of developing the disease if at least one parent carries the mutation.

Mutation: Insertion, KIT gene; 617bp of retrovirus (FERV1) LTR sequences into intron1

Breeds: many breeds

Age of onset of symptoms: White pigmentation present at birth; deafness present at birth.

The Dominant White or W locus in the cat results in complete absence of coat pigmentation, in other words a white cat.  White coat color from the W locus is accepted in numerous cat breeds.  The Dominant White phenotype is fully penetrant and is the result of a 617bp insertion of truncated retroviral sequences within the first intron of the KIT gene.  Blue eyes and congenital sensorial deafness are also associated with the insertion, both being dominant traits with incomplete penetration.  Deafness is due to inner ear degeneration soon after birth and can be partial or complete as well as unilateral or bilateral.  Homozygote W/W cats are uniformly deaf, whereas heterozygote (wwt/W) cats have a 50% chance of having hearing deficits.  Although deafness is particularly associated with white cats with blue eyes, not all white cats have blue eyes and not all blue-eyed cats are deaf.  Indeed, the blue eyes seen within the Siamese breed is not associated with deafness.  Interestingly, full length (7,125bp) of retroviral sequences at the W locus confers white spotting for coat pigmentation and is not associated with deafness.

 

References:

OMIA link: [0259-9685], [0209-9685]

Anderson H, Davison S, Lytle KM, et al. (2022) Genetic epidemiology of blood type, disease and trait variants, and genome-wide genetic diversity in over 11,000 domestic cats.  PLoS Genet. 16;18(6):e1009804.  [pubmed/35709088]

Mari L, Freeman J, Van Dijk J, De Risio L. (2019) Prevalence of congenital sensorineural deafness in a population of client-owned purebred kittens in the United Kingdom. J Vet Intern Med. 33(4):1707-1713 [pubmed/31144374]

Strain GM. (2017) Hearing disorders in cats. J Feline Med Surg 19:276-287. [pubmed/28245737]

Kral A, Lomber SG. (2015) Deaf white cats.  Current Biology 25(9):R351-353. [pubmed/25942543]

Strain GM. (2015) The Genetics of Deafness in Domestic Animals. Front Vet Sci. 2:29. [pubmed/26664958]

David VA, Menotti-Raymond M, Wallace AC et al. (2014) Endogenous retrovirus insertion in the KIT oncogene determines White and White spotting in domestic cats. Genes, Genomes, Genetics 4 :18811891. [pubmed/25085922]