May 6, 2013

The Genetics of Choroideremia

Dr. Ian MacDonald and his team at the University of Alberta are internationally recognized experts in the study of choroideremia, a rare blinding disease that typically affects young men beginning in adolescence. Dr. MacDonald and his team plan to begin the first Canadian clinical trial of a therapy for choroideremia later this year. Your donations are helping to support this trial and this research.

Choroideremia is due to mutations in the REP-1 gene. Many different errors in this gene can lead to choroideremia. At this year’s ARVO meeting, Dr. Paul Freund and Dr. Ian MacDonald, both from the University of Alberta, presented their studies of this genetic variation.

The team identified several new, never-before-observed mutations in this gene. As well, they did a detailed analysis comparing men’s symptoms to the particular type of error in their REP-1 gene. Choroideremia can be a very variable disease, with some men experiencing severe vision loss in young adulthood and others maintaining good vision into late middle age. The scientists were not able to find any significant connections between the mutations and the severity of a person’s symptoms.

As well, the exhaustive evaluation of choroideremia patients in this study gives caregivers more information about the natural course of choroideremia so that they can better advise their patients. For example, the scientists found that men with choroideremia often have relatively intact visual fields until the third decade of life, after which their field of view began to deteriorate significantly. However, they found that severe deterioration in the clarity of a man’s vision rarely happened until the fifth decade of life. Such information is helpful for patients and may also help the team select appropriate patients for the upcoming gene therapy trial.