LINKAGE ANALYSES OF 3 FRENCH FAMILIES TO LOCI ON CHROMOSOME-2P AND CHROMOSOME-3P PREDISPOSING TO HEREDITARY NONPOLYPOSIS COLON-CANCER

: Hereditary, non-polyposis colon cancer (HNPCC) is caused by mutations in different loci. One gene causing HNPCC was mapped to chromosome 2p and recently a tight linkage between a polymorphic marker on the chromosome 3p and the disease locus has been demonstrated and these families also manifest signs of a general DNA replicator disorder. We report detailed genetic studies of three French HNPCC families with D2S123 and D3S1029. In one of the families (F 230), the segregation pattern for markers on chromosomes 2 and 3 suggests absence of linkage. The two other families are not informative enough to conclude on linkage status with chromosomes 2 and 3. If confirmed, this result would mean that the inherited colon cancer in this family is linked to another HNPCC gene. Implication for genetic counselling is discussed. Even with cloned genes, linkage analysis with flanking microsatellite markers for informative families may help to avoid tedious work of seeking point mutations in HNPCC genes.