We observed a hereditary phenotype in Alaskan Huskies that was characterized by polyneuropathy with ocular abnormalities and neuronal vacuolation (POANV). The affected dogs developed a progressive severe ataxia, which led to euthanasia between 8 and 16 months of age. The pedigrees were consistent with a monogenic autosomal recessive inheritance. We localized the causative genetic defect to a 4 Mb interval on chromosome 19 by a combined linkage and homozygosity mapping approach. Whole genome sequencing of one affected dog, an obligate carrier, and an unrelated control revealed a 218-bp SINE insertion into exon 7 of the RAB3GAP1 gene. The SINE insertion was perfectly associated with the disease phenotype in a cohort of 43 Alaskan Huskies, and it was absent from 541 control dogs of diverse other breeds. The SINE insertion induced aberrant splicing and led to a transcript with a greatly altered exon 7. RAB3GAP1 loss-of-function variants in humans cause Warburg Micro Syndrome 1 (WARBM1), which is characterized by additional developmental defects compared to canine POANV, whereas Rab3gap1-deficient mice have a much milder phenotype than either humans or dogs. Thus, the RAB3GAP1 mutant Alaskan Huskies provide an interesting intermediate phenotype that may help to better understand the function of RAB3GAP1 in development. Furthermore, the identification of the presumed causative genetic variant will enable genetic testing to avoid the nonintentional breeding of affected dogs.

Summary A 22‐year‐old Quarter Horse gelding with a history of dental (107) extraction 2 weeks previously was presented with facial cellulitis and an orbital abscess. The abscess was drained surgically dorsally and ventrally to the zygomatic arch and the horse was treated with parenteral antimicrobial and anti‐inflammatory drugs. The affected eye was protected with a temporary tarsorrhaphy and treated via a subpalpebral catheter. Six months after presentation, the horse was in excellent general condition and returned to previous level of exercise but showed blindness on the affected side. Pallor of the optic disc and severe attenuation of the retinal vessels, suggestive of optic disc atrophy, were present.

The prevalence of pectinate ligament dysplasia was evaluated in a prospective multi-center examination of randomly selected Golden retrievers of variable sex and age. The examinations were carried out by qualified veterinary ophthalmologists between May 1 and May 31, 2013. A total of 92 dogs (29 male and 62 female dogs) were examined. The dogs were between 6 months and 14 years old (4.53 ± 3.02 years). Gonioscopy was performed under topical anesthesia using a Koeppe lens and a hand-held slit lamp with 10-x magnification. Four quadrants (dorsal, lateral, medial, ventral) were examined in each eye. For each quadrant a score between 3 (normal) and 0 (grossly abnormal) was assigned. The average total score for all quadrants was 2.14 ±0.95. The width of the drainage angle W was 2.29 ± 0.88, while the score for mesodermal dysplasia MD was 1.98 ± 0.98. There was no significant difference between left and right eyes, however, a significant difference was found between female and male dogs, as well as between young dogs and older dogs. The width of the drainage angle decreased with age and the degree of mesodermal dysplasia increased. Female dogs had lower total scores compared to male dogs and the ventral and lateral quadrants had significantly lower scores than the other quadrants. In conclusion, 52/92 (56.5%) showed signs of Pectinate ligament dysplasia and would have to be excluded from a breeding program according to the guidelines of the European College of Veterinary Ophthalmologists.