Abstract
The first white Doberman pinscher (WDP) dog was registered by the American Kennel Club in 1976. The novelty of the white coat color resulted in extensive line breeding of this dog and her offspring. The WDP phenotype closely resembles human oculocutaneous albinism (OCA) and clinicians noticed a seemingly high prevalence of pigmented masses on these dogs. This study had three specific aims: (1) produce a detailed description of the ocular phenotype of WDPs, (2) objectively determine if an increased prevalence of ocular and cutaneous melanocytic tumors was present in WDPs, and (3) determine if a genetic mutation in any of the genes known to cause human OCA is causal for the WDP phenotype. WDPs have a consistent ocular phenotype of photophobia, hypopigmented adnexal structures, blue irides with a tan periphery and hypopigmented retinal pigment epithelium and choroid. WDPs have a higher prevalence of cutaneous melanocytic neoplasms compared with control standard color Doberman pinschers (SDPs); cutaneous tumors were noted in 12/20 WDP (<5 years of age: 4/12; >5 years of age: 8/8) and 1/20 SDPs (p<0.00001). Using exclusion analysis, four OCA causative genes were investigated for their association with WDP phenotype; TYR, OCA2, TYRP1 and SLC45A2. SLC45A2 was found to be linked to the phenotype and gene sequencing revealed a 4,081 base pair deletion resulting in loss of the terminus of exon seven of SLC45A2 (chr4∶77,062,968–77,067,051). This mutation is highly likely to be the cause of the WDP phenotype and is supported by a lack of detectable SLC45A2 transcript levels by reverse transcriptase PCR. The WDP provides a valuable model for studying OCA4 visual disturbances and melanocytic neoplasms in a large animal model.
Highlights
The Doberman pinscher dog breed was originally developed in the 1880s by Karl Dobermann of Thuringen, Germany, for the purpose of protection in his job as a tax collector and night watchman
Biomicroscopy showed all white Doberman pinscher (WDP) had hypopigmented adnexal structures including eyelid margins, leading edge of the nictitating membrane, and cilia (Figure 2 B); whereas these structures were darkly pigmented in standard color Doberman pinschers (SDPs) (Figure 2 F)
The irides of all WDPs were tan in the peripheral ciliary zone transitioning to blue towards the pupillary zone, the pupils showed verticallyoriented ovoid dyscoria, and had patchy stromal thinning adjacent to the pupillary aperture (Figure 2 B); these areas of stromal thinning were observed to transilluminate with retro-illumination during the ocular examinations
Summary
The Doberman pinscher dog breed was originally developed in the 1880s by Karl Dobermann of Thuringen, Germany, for the purpose of protection in his job as a tax collector and night watchman. As part of the official breed standard, major international breed clubs, including the Doberman Pinscher Club of America (a member of the American Kennel Club), recognize only coat colors of black, blue, red, and fawn. In 1976, a female Doberman pinscher with novel ‘‘white’’ coat-coloration was born and registered with the American Kennel Club. The uniqueness of the light coat-color prompted breeders to utilize line breeding to maintain the phenotype, resulting in an extensive pedigree in which all living white Doberman pinschers (WDPs) are traceable to this initial white female. Subsequent suspicion arose that the phenotype was a form of albinism, setting off a controversy among Doberman pinscher breeders surrounding breeding recommendations for WDPs
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