Chromosome 4q;10q translocations; Comparison with different ethnic populations and FSHD patients

BACKGROUND Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant disorder characterized by the weakness of facial, shoulder-girdle and upper arm muscles. Most patients with FSHD have fewer numbers of tandem repeated 3.3-kb KpnI units on chromosome 4q35. Chromosome 10q26 contains highly homologous KpnI repeats, and inter-chromosomal translocation has been reported. METHODS To clarify the influence on the deletion of the repeats, we surveyed three different ethnic populations and FSHD patients using the BglII/BlnI dosage test. RESULTS The frequency of translocation in 153 Japanese, 124 Korean, 114 Chinese healthy individuals and 56 Japanese 4q35-FSHD patients were 27.5%, 29.8%, 19.3%, and 32.1%, respectively. The ratio of '4 on 10' (trisomy and quatrosomy of chromosome 4) was higher than that of '10 on 4' (nullsomy and monosomy of chromosome 4) in all populations. CONCLUSIONS The inter-chromosomal exchange was frequently observed in all four populations we examined, and no significant difference was observed between healthy and diseased groups.