Isolation of NotI sites from chromosome 22q11.

Chromosome 22q11 contains a large number of interesting loci, including genes associated with cancer and developmental defects. The region is also the site of the lambda immunoglobulin variable and constant regions and the BCR, gamma-glutamyl transpeptidase, and GGT-like activity multigene families. Because of the complexities associated with mapping highly related gene families, we have examined the utility of mapping large areas of DNA using a defined approach. A total of 21 complete NotI sites from band q11 were cloned and ordered into six noncontiguous clusters of sites using a combination of somatic cell hybrid panels, NotI jumping and linking libraries, and fluorescence in situ hybridization. The largest cluster spanned an estimated 2 Mb of NotI fragments, the smallest 115 kb. Approximately 3.5 Mb of band q11 could be examined for rearrangements in NotI restriction enzyme fragments. A number of conserved sequences, two genes, and a minimum of two families of related sequences were identified adjacent to NotI sites.