The von Recklinghausen neurofibromatosis 1 (NFI) locus has been previously assigned to the proximal long arm of chromosome 17, and two NF1 patients have been identified who have constitutional balanced translocations involving 17q11.2. We have constructed a cosmid library from a chromosome-mediated gene transfectant, KLTS, that contains approximately 10% of chromosome 17, including 17q11.2. Cosmids isolated from this library have been mapped across a panel of somatic cell hybrids, including the hybrids from the two patients, and have been localized to seven small regions of proximal 17q. We have 5 cosmids that map directly above the two NFI translocations, and 11 cosmids that map directly below. Of these, 2 cosmids in each region are linked to the disease locus and 3 of these cosmids show no recombination.One distal cosmid, 2B/B35, detects the two NFI translocations by pulsed-field gel analysis and has been used to produce a long-range restriction map that covers the translocations.Von Recklinghausen neurofibromatosis 1 (NF1) is one of the most common dominantly inherited disorders in man with an estimated frequency of 1/3000 and a high proportion of new mutations, estimated between 30 and 50%o (1). Its expression is extremely variable, even within affected families, and ranges from minor skin manifestations (e.g., cafe-au-lait spots) to severely disabling and sometimes lethal neurological tumors. Linkage of this disorder to markers on proximal 17q has been demonstrated (2, 3) and linked flanking markers have been defined (4, 5). As with several other dominantly inherited tumor-forming syndromes (e.g., retinoblastoma or adenomatous polyposis coli), it seemed likely that NF1 might be the result of mutations in a tumor-suppressor gene. However, there are as yet no reports of loss of heterozygosity in NF1 for markers close to the NFI locus.The finding of two individuals with NF1 carrying different constitutional balanced reciprocal translocations with breaks at 17q11.2 (6, 7) strongly suggested that the region of these translocations would contain the NFI gene. Probes that map close to the translocations have been used to make long-range maps of this region (8,9). By using a chromosome-mediated gene transfectant (CMGT), KLT8, containing about 10% of chromosome 17, including the NFl region (10), we have isolated cosmids flanking the NFI translocations. Restriction fragment length polymorphisms (RFLPs) in these cosmids have allowed us to map them by genetic linkage. Our closest probe lies distal to the translocations and has no recombinants with NFI. It contains a CpG-rich island and has been used by analysis of pulsed-field gel electrophoresis (PFGE) results to define a long-range restriction map covering the translocations that differ from the published maps (27). In this paper we present the genetic linkage data on our flanking probes and our physical map of the translocation region.
MATERIALS AND METHODSCell Lines. KLT8, PLT6B, and PLT8 are CMGTs containing fragments of chromosome 17 (10). PCTBA1.8 (11) i...