Time and space clusters of the French-Canadian M1V phenylketonuria mutation in France.

We performed mutation analysis and RFLP haplotype analysis of chromosomes associated with classical phenylketonuria (PKU) in contemporary French families. We also did genealogical reconstructions for seven obligate carriers in five contemporary French-Canadian families living in eastern Quebec, who carry the M1V mutation causing PKU. The M1V mutation, heretofore considered to be associated exclusively with French-Canadians, was found on 4 of 152 independent French chromosomes. The French and Quebec M1V mutations all occurred on RFLP haplotype 2. The contemporary mutant French chromosomes clustered in southern Brittany (Finistère Sud). Genealogical reconstructions of the Quebec families identified 53 shared ancestors and a center of diffusion in the Perche region in 17th century France. The two clusters in France, one historical and the other contemporary, are not incompatible, if one assumes the possibilities that settlers returned from Nouvelle France or moved from Perche to southern Brittany. The M1V mutation is serving as a useful marker for historical demography.