A single mutation of the fumarylacetoacetate hydrolase gene in French Canadians with hereditary tyrosinemia type I
Grompe, M.; St-Louis, M.; Demers, S.I.; al-Dhalimy, M.; Leclerc, B.; Tanguay, R.M.
New England Journal of Medicine 331(6): 353-357
ISSN/ISBN: 0028-4793 PMID: 8028615 DOI: 10.1056/nejm199408113310603
Hereditary tyrosinemia type I is an autosomal recessive inborn error of metabolism caused by a deficiency of the enzyme fumarylacetoacetate hydrolase. The disorder clusters in the Saguenay-Lac-St.-Jean area of Quebec. In this region, 1 of 1846 newborns is affected and 1 of every 22 persons is thought to be a carrier. Recently, we identified a splice mutation and two nonsense mutations in the fumarylacetoacetate hydrolase gene in two patients from Quebec with tyrosinemia type I. We used allele-specific-oligonucleotide hybridization to examine the frequency of these three candidate mutations in patients with tyrosinemia type I and in the population of Quebec. The splice mutation was found in 100 percent of patients from the Saguenay-Lac-St.-Jean area and in 28 percent of patients from other regions of the world. Of 25 patients from the Saguenay-Lac-St.-Jean region, 20 (80 percent) were homozygous for this mutation, a guanine-to-adenine change in the splice-donor sequence in intron 12 of the gene, indicating that it causes most cases of tyrosinemia type I in the region. The frequency of carrier status, based on screening of blood spots from newborns, was about 1 per 25 in the Saguenay-Lac-St.-Jean population and about 1 per 66 overall in Quebec. This study identified the most prevalent mutation causing hereditary tyrosinemia in French Canada; it also showed the feasibility of DNA-based testing for carriers in the population at risk.