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Oculocutaneous Albinism German Spitz Type (OCA2)
| Acronym: | OCA2 |
| Gene: | OCA2 |
| Mutation: | g.31715704A>C |
| Inheritance: | Autosomal recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Oculocutaneous Albinism German Spitz Type (OCA2) is a form of albinism, a disorder of melanin production, affecting this dog breed. It is characterized by hypopigmentation in the skin, hair, and eyes. OCA2 is known to affect also human patients, where it is known as brown oculocutaneous albinism, with the highest prevalence recorded in Africa. Other breeds affected by different forms of oculocutaneous albinism are Doberman pinscher, Leonberger, Rottweiler, Great Dane, German Spitz, Lhasa Apso, Pekingese, and Pomeranian, and in almost every breed, the disorder is caused by a different, breed-specific mutation. In several other species, including mice, humans, rabbits, cattle, and cats, albinism is associated with a mutation within the tyrosinase gene. OCA2-affected German spitz has light brown coat color, light lips and noses, and blue eyes which turn into green with age. Pupils in the eyes appear reddish in color. Dogs display symptoms of photophobia and show difficulties in perceiving hand signals in bright sunlight.
Oculocutaneous Albinism German Spitz type is caused by guanine to adenine substitution in the conserved 5’-splice site of the first intron of the canine OCA2 gene. OCA2 encodes for OCA2 protein, a transmembrane protein within melanosomes, where it is a putative anion transporter. As such, OCA2 plays a role in melanosome biogenesis, melanosomal pH regulation, and eumelanin synthesis and is crucial for the normal processing and transport of other melanosomal proteins. The disorder is inherited in an autosomal recessive pattern. Healthy parents of an affected dog are obligate heterozygotes and therefore carry one mutant allele. Heterozygotes are carriers and show no symptoms. At conception, each cub has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (i.e. two pairs of healthy alleles). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
CARRIER |
Tested mutation was detected in animal with „carrier“ result. Animal tested as carrier has one wild-type and one mutation allele, it is in heterozygous state. It will not develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has two copies of mutation alleles affecting the gene. It is likely the animal will experience a genetic disorder due to this mutation.** It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
** Potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Caduff M, Bauer A, Jagannathan V, Leeb T (2017) OCA2 splice site variant in German Spitz dogs with oculocutaneous albinism. PLoS ONE 12 (10): e0185944. https://doi.org/10.1371/journal. pone.0185944