FINE MAPPING OF THE FSHD GENE REGION ORIENTATES THE REARRANGED FRAGMENT DETECTED BY THE PROBE P13E-11

We have produced a fine restriction map around the locus D4F104S1 (pre viously designated D4S810); a probe to this locus, p13E-11, identifies a polymorphic EcoRI fragment containing 3.2kb tandem repeats and dete cts DNA rearrangements associated with facioscapulohumeral muscular dy strophy (FSHD). We developed an STS (D4F106S1) which maps 2kb proximal to D4F104S1, and used this to isolate a 470kb YAC (y25C2E) from the I CI YAC library and a 930kb YAC (y956A11) from the CEPH megabase librar y. Both YACs contain the loci D4Sl39, D4F35S1 and D4F104S1. A cosmid l ibrary was produced from YAC y25C2E and two cosmid contigs constructed ; a 115kb contig encompassing D4Sl39, and one of 135kb linking D4F35S1 and D4F104S1 and extending distal to the EcoRI fragment detected by p 13E-11. A fine restriction map of both these contigs has been generate d, allowing the orientation of the EcoRI fragment rearranged in FSHD t o be determined. YAC y956A11 was used to confirm the integrity of y25C 2E and the map of this region. 9B6A, a probe to the homeobox region of the tandem repeat D4Z4, identified a cross-hybridising sequence proxi mal to D4F104S1, however, p13E-11 does not detect this additional locu s. CpG islands were identified between D4Sl39 and D4F35S1 and within e ach copy of the tandem repeat. The probe 9B6A detected each copy of th e repeat motif, suggesting there is homeobox present in every copy of the 3.2kb repeat.