LOCALIZATION OF THE TRANSLOCATION BREAKPOINT IN A FEMALE WITH MENKES SYNDROME TO XQ13.2-Q13.3 PROXIMAL TO PGK-1

Menkes syndrome is a rare X-linked recessive disorder characterized by an inability to metabolize copper. A female patient with both this disease and an X; autosome translocation with karyotype 46,X,t(X;2)(q13; q32.2) has previously been described. The translocation breakpoint in Xq13 coincides with a previous assignment of the Menkes gene at Xq13 by linkage data in humans and by analogy to the mottled mutations which are models for Menkes disease in the mouse. Therefore, this translocation probably interrupts the gene for Menkes syndrome in band Xql3. We describe here experiments to precisely map the translocation breakpoint within this chromosomal band. We have established a lymphoblastoid cell line from this patient and have used it to isolate the der(2) translocation chromosome (2pter --> 2q32::Xq13 --> Xqter) in human/hamster somatic cell hybrids. Southern blot analyses using a number of probes specific for chromosomes X and 2 have been studied to define precisely the location of the translocation breakpoint. Our results show that the breakpoint in this patient-and, therefore, likely the Menkes gene-maps to a small subregion of band Xql3.2-ql3.3 proximal to the PGK1 locus and distal to all other Xq13 loci tested.