Regional mapping of human genes for hexosaminidase B and diphtheria toxin sensitivity on chromosome 5 using mouse × human hybrid cells

Mouse 3T3 (TK^–) cells were fused to human leukocytes containing a balanced translocation [ins(3;5) (q27;q13q15)] in which part of the long arm of a chromosome 5 has been inserted into the long arm of a chromosome 3. Two independent, primary hybrid clones (XVI-10C; XVI-18A) retained the deleted chromosome 5 [del(5) (q13q15)] translocation product and were informative for regional mapping on chromosome 5 of genes involved in expression of hexosaminidase B (HEX_B) and diphtheria toxin sensitivity (DTS). Both XVI-10C and XVI-18A clones were sensitive to diphtheria toxin. Toxin-resistant derivatives of these clones (XVI-10C DTR; XVI-18A DTR) were analyzed for chromosome content and expression of Hex B activity, as were XVI-10C and XVI-18A cells which had not been exposed to diphtheria toxin. The results of this study provide evidence for localization ofDTS to region 5q155qter on the long arm of chromosome 5, and localization ofHEX_B to region 5pter5q13.