ATAXIA-TELANGIECTASIA - FOUNDER EFFECT AMONG NORTH-AFRICAN JEWS

The ATM gene is responsible for the autosomal recessive disorder ataxi a-telangiectasia (A-T), characterized by cerebellar degeneration, immu nodeficiency and cancer predisposition, A-T carriers were reported to be moderately cancer-prone, A wide variety of A-T mutations, most of w hich are unique to single families, were identified in various ethnic groups, precluding carrier screening with mutation-specific assays, Ho wever, a single mutation was observed in 32/33 defective ATM alleles i n Jewish A-T families of North African origin, coming from various reg ions of Morocco and Tunisia, This mutation, 103C-->T, results in a sto p codon at position 35 of the ATM protein. In keeping with the nature of this mutation, various antibodies directed against the ATM protein failed to detect this protein in patient cells, A rapid carrier detect ion assay detected this mutation in three out of 488 ATM alleles of Je wish Moroccan or Tunisian origin. This founder effect provides a uniqu e opportunity for population-based screening for A-T carriers in a lar ge Jewish community.