Oculopharyngeal MD among Bukhara Jews is due to a founder (GCG)9 mutation in the PABP2 gene

Objective: To determine whether all cases of oculopharyngeal muscular dystr ophy (OPMD) among Bukhara Jews share the same founder mutation. Background: Autosomal dominant OPMD is caused by a (GCG)(8-13) repeat expansion in the polyadenylation binding protein 2 (PABP2) gene. The disease has a worldwid e distribution but is particularly prevalent in Bukhara Jews and in French Canadians, in whom it was introduced by three sisters in 1648. Methods: We established the size of the PABP2 mutation in 23 Bukhara Jewish patients be longing to eight unrelated families. In all families, we constructed haplot ypes for the carrying chromosomes composed of the alleles for eight chromos ome 14q polymorphic markers. Results: All patients share a (GCG)(9), PABP2 mutation and a four-marker haplotype. Furthermore, a shared intron single n ucleotide polymorphism (SNP) in the PABP2 gene 2.6Kb from the mutation was not observed in 22 families with (GCG)(9) mutations from nine different cou ntries. The smaller size of the chromosomal region in linkage disequilibriu m around the mutation in Bukhara Jews, as compared with French Canadians, s uggests a founder effect that occurred more than 350 years ago. Based on th e Luria-Delbruck corrected "genetic clock," we estimate that the mutation a ppeared or was introduced once in the Bukhara Jewish population between AD 872 and 1512 (mean, AD 1243). Conclusion: OPMD among Bukhara Jews is the re sult of a shared, historically distinct, PABP2 (GCG), mutation that likely arose or was introduced in this population at the time they first settled i n Bukhara and Samarkand during the 13th or 14th centuries.