Deafblindness in French Canadians from Quebec: a predominant founder mutation in the USH1C gene provides the first genetic link with the Acadian population.

Background: Usher syndrome type 1 (USH1) is the leading cause of deafblindness. In most populations, many private mutations are distributed across the five known USH1 genes. We investigated patients from the French Canadian population of Quebec (approximately 6 million people) that descends from about 8,500 French settlers who colonized the St Lawrence River valley between 1608 and 1759.