DELETION CARTOGRAPHY AROUND THE D13S25 LOCUS IN B-CELL CHRONIC LYMPHOCYTIC-LEUKEMIA AND ACCURATE MAPPING OF THE INVOLVED TUMOR-SUPPRESSOR GENE

The presence of an unidentified tumor suppressor gene on the long arm of chromosome 13 which could be involved in the development of B cell chronic lymphocytic leukemia has been suspected because of frequent de letions of the locus D13S25 which lies 1.6 cM telomeric to the retinob lastoma gene. In order to accurately map this gene, cells from 25 B ce ll chronic lymphocytic leukemia tumors have been analyzed for allelic loss using a panel of microsatellite markers located in this region. T hese markers, which stretch from the retinoblastoma gene to the Wilson disease gene, have been ordered for their rank from centromere to tel omere. In addition to the data obtained from deletion pattern of these markers, results from preliminary pulse-field electrophoresis studies enable us to redefine the minimal deleted area from more than 1 cM to 280 kilobase around D13S25.