Oculocutaneous Albinism German Spitz Type (OCA2)
Oculocutaneous Albinism German Spitz Type (OCA2) is a form of albinism, disorder of melanin production, affecting this dog breed. It is characterized by hypopigmentation in skin, hair and eyes. OCA2 is known to affect also human patients, where it is known as brown oculocutaneous albinism, with 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 each 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 to mutation within tyrosinase gene.
OCA2 German Spitz Type Characteristics and Symptoms
OCA2 affected German spitzs have light brown coat colour, light lips and noses and blue eyes which turn into green with age. Pupils in eyes appear of reddish colour. Dogs display symptoms of photophobia and show difficulties of perceiving hand signals in bright sunlight.
Oculocutaneous Albinism German Spitz type is caused by a 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 normal processing and transport of other melanosomal proteins.
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.