To better map the location of the von Recklinghausen neurofibromatosis (NF1) 
gene, we have characterized a somatic cell hybrid designated 7AE-11. This 
microcell-mediated, chromosome-transfer construct harbors a centromeric segment 
and a neo-marked segment from the distal long arm of human chromosome 17. We 
have identified 269 cosmid clones with human sequences from a 7AE-11 library 
and, using a panel of somatic cell hybrids with a total of six chromosome 17q 
breakpoints, have mapped 240 of these clones on chromosome 17q. The panel 
included a hybrid (NF13) carrying a der(22) chromosome that was isolated from an 
NF1 patient with a balanced translocation, t(17;22) (q11.2;q11.2). Fifty-three 
of the cosmids map into a region spanning the NF13 breakpoint, as defined by the 
two closest flanking breakpoints (17q11.2 and 17q11.2-q12). RFLP clones from a 
subset of these cosmids have been mapped by linkage analysis in normal reference 
families, to localize the NF1 gene more precisely and to enhance the potential 
for genetic diagnosis of this disorder. The cosmids in the NF1 region will be an 
important resource for testing DNA blots of large-fragment restriction-enzyme 
digests from NF1 patient cell lines, to detect rearrangements in patients' DNA 
and to identify the 17;22 NF1 translocation breakpoint.