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Molecular Genetic Study of Coloboma in the Dog

Gustavo Aguirre, VMD, PhD
University of Pennsylvania
OptiGen, LLC

Collie Eye Anomaly (CEA) is an autosomal recessive disease affecting a number of dog breeds. Even though not all of these breeds are collie related, we use the generic term CEA to phenotypically characterize the disease. The disease has 3 major phenotype components: choroidal hypoplasia (CH), coloboma/staphyloma/posterior scleral ectasia (coloboma) and retinal detachment. The frequency of the 3 phenotype components varies, with CH being most frequent, and detachments least frequent. The basic CEA lesion is, in fact, CH, and this abnormality must be present in dogs with coloboma and/or retinal detachment for the latter two severe conditions to be considered related to CEA. It should be noted that there are also other causes of coloboma and retinal detachment that are unrelated to CEA.

We previously identified the molecular defect responsible for CEA as being caused by a 7.8 kb homozygous deletion in the NHEJ1 gene. Testing for this mutation informs on CH, but not on the other phenotype components of the disease. The working hypothesis is that colobomas result from a mutation or sequence change in a second modifier gene(s) that requires that the homozygous deletion in the NHEJ1 gene is present. The aim of this research is to identify the modifier locus/gene.

The following breeds/varieties are known to be affected with CEA based on DNA testing and would be included in the study*:

Australian Shepherds

Collies, Rough

Nova Scotia Duck Tolling Retrievers

Australian Shepherds, Miniature

Collies, Smooth

Shetland Sheepdogs

Australian Shepherds, Toy

Farm Collies

Silken Windhounds

Bearded Collies

Hokkaido Dogs

Whippets, Longhaired

Border Collies

Lancashire Heelers


Boykin Spaniels

Miniature American Shepherds


*Note: samples from other breeds in which a diagnosis of coloboma accompanying CH is made also will be accepted for the study.

Your help is needed
To carry out this study we need the assistance of dog owners/breeders, as well as board certified veterinary ophthalmologists (ACVO, ECVO) so that samples for the research study can be definitively ascertained. We are very grateful for your interest in participating in the present research study. Please make sure that only one form is used for each study dog.

A research form for submitting samples and information for this study can be found on the OptiGen website at Coloboma Research. The owner should complete the first section of owner and dog information. The second section of the form requests the examining ophthalmologist to provide brief clinical descriptions and, if possible, clinical photographs. Along with the completed form, we need a copy of the dog's pedigree (5-6 generations), any current/previous eye exam records, and 3-5 ml of whole unclotted blood in EDTA to be sent to OptiGen, 767 Warren Road, Suite 300, Ithaca, NY 14850. Please call OptiGen at 607-257-0301 or email with any questions on sample submission.

NOTE: all the information provided for this study is CONFIDENTIAL and will not be disclosed.

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