Canavan disease: carrier-frequency determination in the Ashkenazi Jewish population and development of a novel molecular diagnostic assay.
Canavan disease (CD) is an autosomal recessive progressive neurodegenerative disorder prevalent in the Ashkenazi Jewish (AJ) population. The carrier rate for the most common mutations that cause CD in the AJ population is often quoted as 1:37-1:40. This is not supported by our finding of only two diagnosed cases of CD in the last 20 years in the Toronto AJ population of 160,000 and an estimated birth rate of 1,500-2,000 per year. Therefore, we embarked on a prevalence cross-sectional screening study to determine the carrier rate of CD in this population. In order to perform low-cost, high-throughput population testing for CD using molecular techniques, we first developed a novel molecular assay using multiplex fluorescent allele specific polymerase chain reaction (PCR) to test for the three most common mutations causing CD in the AJ population (A854C, C693A, C914A) and a neutral polymorphism at the site of the C693A mutation. During testing it was noted that individuals who were carriers of the A854C mutation also had a T polymorphism at the site of the C693A mutation (Y231X). We confirmed that in all A854C carriers the 854C mutation was in disequilibrium with the 693T polymorphism, indicating a founder chromosome for the A854C mutation in the AJ population. Twenty-five carriers were found from 1,423 samples yielding a carrier rate of 1:57, differing from the widely quoted frequency of 1:40 and supporting our observed frequency of disease.
Feigenbaum
Annette
A
Division of Clinical and Metabolic Genetics, Department of Pediatrics, The Hospital For Sick Children, The University of Toronto, Toronto, Canada. asjf@sickkids.ca
Moore
Robert
R
Clarke
Joe
J
Hewson
Stacy
S
Chitayat
David
D
Ray
Peter N
PN
Stockley
Tracy L
TL
D000483:Alleles; D000581:Amidohydrolases / Q000235:genetics; D017825:Canavan Disease / Q000175:diagnosis / Q000235:genetics*; D004247:DNA / Q000737:chemistry / Q000235:genetics; D004252:DNA Mutational Analysis; D005787:Gene Frequency; D006580:Genetic Carrier Screening / Q000379:methods; D005820:Genetic Testing / Q000379:methods*; D006579:Heterozygote; D006801:Humans; D007585:Jews / Q000235:genetics*; D009154:Mutation; D011110:Polymorphism, Genetic
D004247:DNA; D000581:Amidohydrolases; C019751:aspartoacylase