A chromosome jump crosses a translocation breakpoint in the von recklinghausen neurofibromatosis region

Abstract
The von Recklinghausen neurofibromatosis (NF1) gene has been previously localized to the region 17q11.2 by genetic analysis. Consistent with this, two NF1 patients have been described with autosomal translocations with breakpoints in 17q11.2, and these represent presumed markers for the location of the NF1 gene. Recent work has defined the two breakpoints on a physical map, and they lie less than 100 kb apart. To characterize further the distance between these breakpoints and clone additional DNA, a chromosome jump was made from a DNA fragment that maps between the breakpoints. The end of the jump crosses one of the NF1 translocation breakpoints and detects that breakpoint on Southern analysis, placing the probe less than 15 kb telomeric to this breakpoint. Pulsed field analysis with the jump clone allows revision of the previous NF1 region map and indicates that the two breakpoints lie no more than 60 kb apart. This jump clone will be useful for further mapping, breakpoint cloning, analysis of patient DNA, and the search for transcripts in the NF1 region.