Derivation of clones from the choroideremia locus by preparative field inversion gel electrophoresis

By making use of preparative field inversion gel electrophoresis, we have constructed a lambda ZAP library that is highly enriched for sequences from the choroideremia locus. In vivo excision of pBluescript SK(-) constructs from lambda ZAP obviates the subcloning of DNA inserts and allows for rapid processing of several hundred recombinants. From a 625 kb Sfil fragment we isolated 7 clones that were physically mapped using microdeletions associated with the disease. One of these clones is located within, or just telomeric to, the choroideremia gene and detects two restriction fragment length polymorphisms (RFLPs). Another clone detects a RFLP which maps centromeric to the disease locus. Together these probes should improve the reliability of linkage analysis in choroideremia families and should pave the way for the isolation of the choroideremia gene.