Epilepsy phenotypes in siblings with Norrie disease.
Mutations at the Norrie disease gene locus, NDP, manifest in a broad range of defects. These range from a relatively mild, late-onset, exudative vitreoretinopathy to congenital blindness and sensorineural deafness combined, in some cases, with mental retardation. In addition, extensive deletions involving the NDP locus, located at Xp11.3, the adjacent monoamine oxidadase genes MAOA and MAOB, and additional material, result in a more severe pattern of symptoms. The phenotypes include all or some of the following; mental retardation, involuntary movements, hypertensive crises and hypogonadism. We extended an existing YAC contig to embrace the boundaries of three of the largest deletions and converted this into four PAC contigs. Computer analysis and experimental data have resulted in the identification of several putative loci, including a phosphatase inhibitor 2-like gene (dJ154.1) and a 250-bp sequence which resembles a homeobox domain (dA113.3), 1.2 Mb and 400 kb respectively from the MAO/NDP cluster. The pattern of expression of dJ154.1 suggests that it may represent an important factor contributing to the complex phenotypes of these deletion patients. Hum Mutat 17:523, 2001.