Multiple congenital ocular anomalies in Icelandic horses

BMC Veterinary Research

Research Article

Jeanette Axelsson¹  Gabriella Lindgren¹  Lisa S Andersson¹  Björn Ekesten²  Richard R Dubielzig³ 

[1] Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Box 597, SE-751 24, Uppsala, Sweden;Department of Clinical Sciences, Swedish University of Agricultural Sciences, Box 7054, SE-750 07, Uppsala, Sweden;Department of Pathobiological Sciences, School of Veterinary Medicine, Comparative Ocular Pathology Laboratory of Wisconsin, University of Wisconsin-Madison, WI 53706-1102, 2015 Linden Drive, Madison, USA;

关键词: Peripheral Retina;    Tropicamide;    Temporal Quadrant;    Horse Breed;    Pupillary Light Reflex;   

DOI  :  10.1186/1746-6148-7-21

 received in 2011-02-28, accepted in 2011-05-26,  发布年份 2011

来源: Springer

【 摘 要 】

BackgroundMultiple congenital ocular anomalies (MCOA) syndrome is a hereditary congenital eye defect that was first described in Silver colored Rocky Mountain horses. The mutation causing this disease is located within a defined chromosomal interval, which also contains the gene and mutation that is associated with the Silver coat color (PMEL17, exon 11). Horses that are homozygous for the disease-causing allele have multiple defects (MCOA-phenotype), whilst the heterozygous horses predominantly have cysts of the iris, ciliary body or retina (Cyst-phenotype). It has been argued that these ocular defects are caused by a recent mutation that is restricted to horses that are related to the Rocky Mountain Horse breed. For that reason we have examined another horse breed, the Icelandic horse, which is historically quite divergent from Rocky Mountain horses.ResultsWe examined 24 Icelandic horses and established that the MCOA syndrome is present in this breed. Four of these horses were categorised as having the MCOA-phenotype and were genotyped as being homozygous for the PMEL17 mutation. The most common clinical signs included megaloglobus, iris stromal hypoplasia, abnormal pectinate ligaments, iridociliary cysts occasionally extending into the peripheral retina and cataracts. The cysts and pectinate ligament abnormalities were observed in the temporal quadrant of the eyes. Fourteen horses were heterozygous for the PMEL17 mutation and were characterized as having the Cyst-phenotype with cysts and occasionally curvilinear streaks in the peripheral retina. Three additional horses were genotyped as PMEL17 heterozygotes, but in these horses we were unable to detect cysts or other forms of anomalies.One eye of a severely vision-impaired 18 month-old stallion, homozygous for the PMEL17 mutation was examined by light microscopy. Redundant duplication of non-pigmented ciliary body epithelium, sometimes forming cysts bulging into the posterior chamber and localized areas of atrophy in the peripheral retina were seen.ConclusionsThe MCOA syndrome is segregating with the PMEL17 mutation in the Icelandic Horse population. This needs to be taken into consideration in breeding decisions and highlights the fact that MCOA syndrome is present in a breed that are more ancient and not closely related to the Rocky Mountain Horse breed.

【 授权许可】

CC BY   
© Andersson et al; licensee BioMed Central Ltd. 2011