Physical mapping of the Gorlin syndrome region on 9q22 by pulsed field gel electrophoresis (PFGE) and FISH

Gorlin syndrome is an autosomal dominant disorder characterized by basal cell carcinomas, medulloblastomas, and ovarian fibromas, as well as widespread developmental defects. Linkage and tumor deletion studies localized the gene for this syndrome to the 3 cM region on chromosome 9q22 between D9S196 and D9S180. Several groups have constructed YAC contigs of this region, but many of the YACs are known to contain rearrangements. Mapping by PGE and FISH is useful in further characterization of the relationship between physical distance and genetic distance. We isolated seven cosmids mapping to this region (D9S180, D9S196, D9S287, Col 15A1, XPA and two new anonymous cosmids). FISH gave a distance between D9S196 and D9S180 of at least 2 Mb and showed that Col15A1, previously considered as a candidate gene, mapped a few hundred kb distal to S180. For PFGE, DNA blocks from normal and 20 Gorlin syndrome patients were digested with 5 restriction enzymes and probed with single copy fragments of the seven cosmids. No aberrant bands have been identified in patients. Non-overlapping Not I fragments from these seven markers totalled 2.3 kb. Given an average gene density, a region of this size would contain 50-100 genes.