CHARACTERIZATION OF X-17(Q12-P13) TRANSLOCATION BREAKPOINTS IN A FEMALE-PATIENT WITH HYPOMELANOSIS OF ITO AND CHOROID-PLEXUS PAPILLOMA

An X;17 translocation breakpoint was characterised in a 5-year-old fem ale with hypomelanosis of Ito (HI) who exhibits characteristic hypopig mented lesions, psychomotor retardation, and choroid plexus papilloma, A YAC clone containing the locus DXS1 from Xq12 was found by fluoresc ence in situ hybridisation to cross the translocation breakpoint. Cosm id clones positive for DXS1 were used to identify and clone the transl ocation junction fragment from the patient's DNA. A chromosome-17-spec ific DNA fragment was isolated and used to identify cosmid clones cros sing the translocation from chromosome 17p13. Exon trapping identified two known genes from chromosome 17: FMR1L2 (the fragile X mental reta rdation syndrome like protein 2) and SHBG (human sex hormone-binding g lobulin), Mapping the FMR1L2 and SHBG genes showed that neither gene w as disrupted by the translocation.