Identification of novel rhodopsin mutations associated with retinitis pigmentosa by GC-clamped denaturing gradient gel electrophoresis.

Retinitis pigmentosa (RP) is a group of disorders characterized by progressive degeneration of the outer retina, resulting in night blindness, visual field loss, an abnormal electroretinogram, and characteristic retinal pigmentary changes. An important step in the understanding of RP has been the recognition that some cases of autosomal dominant RP (ADRP) are caused by mutations in the rhodopsin gene. Multiple different point mutations within the coding sequence of the rhodopsin gene have been associated with ADRP. We have developed a GC-clamped denaturing-gradient-gel electrophoresis (DGGE) assay for the coding region of the rhodopsin gene and have used this assay to screen ADRP patients for mutations. The assay consists of amplifying with PCR the five exons of the rhodopsin gene and then analyzing each PCR product by DGGE. We have used this assay to detect three previously unreported rhodopsin base substitutions associated with ADRP. The use of this assay to identify ADRP patients who have various rhodopsin mutations has allowed us to begin studies seeking to correlate molecular genotype with clinical phenotype. Furthermore, GC-clamped DGGE has allowed us to identify families with ADRP not caused by a rhodopsin mutation. Such families will be important in the search for other genes involved in ADRP.