The Study Of Loca Lization Of Autosomal Dominant Retinitis Pigmentosa Gene And Detection Of Mutation On Rhodopsin Gene

Retinitis pigmentosa is a group of inherited degenerative retinal disorders characterized by loss of functions of photoreceptor and pigmentary epitheliuni. Affected individuals typically display night blindless, progressive reduction of the visual field, pigment deposition in retina and abnormal ERG. This study emphasizes on autosomal dominant retinitis pigmentosa (ADRP). We studied a large family with ADRP which had donated blood specimens for molecular genetic studies of their leukocyte DNA. We collected 5m1 of venous blood from some family members, and genomic DNA was extracted from the bloods using VIOGENE DNA Extraction Kit. Microsateliite markers from known ADRl~ loci were then typed in the family by PCR amplification. Two-point linkage analysis between each marker and the disease locus was performed by using of the MLINK program of the LINKAGE package version 5.1, from which we can determine the disease gene loci on the chromosome. Linkage analysis showed three adjacent marker on chromosome 3q provide a positive LOD score(D3S 1569, D3S1267, D3S1292). The maximum LOt) score reaches 2.732852 at marker D3S 1292 (at recombination fraction 8 =0.1). For the rhodopsin gene had been reported as linked to 3q21, then mutation screening of rhodopsin was carried out by direct gcnomic sequencing of PCR amplified exons using a sequencing kit. Sequence was determined from affected individuals and compared with sequence from healthy individuals and with the published sequence.The result showed a guanine-to-adenine transition mutation in codon 182 in exon 3 of the rhodopsin gene that resulted in a glycine to aspartic change(Gly- 182-Asp) in affected individuals only. But we did not identify the change in the normal family members. The mutation involve amino acid clustered within the intradiscal domain of the photoreceptor 3 Which are likely to be rhodopsin gene mutaions resulting in RP, for twO reasons. First, themutation was foUnd in dsted individuals only, but nO fOUnd in Untwd individuals inthe same family. SecOnd. we did nOt detect Other mutaions within the coding region ofrhodOpsin gene. The IiIhage of ADRP with a genetic marker near the thodPSin gene andthe subsequent identification OfboPSin coding Seqec mhons in ADRP halieswere major advances toWar undrStallding human retinal degenerations at the moIecularIeveI. The recoghon of speific mutations in the thodOPSin gen tha cause some forms ofgy is encouraging frOm three persPectves. FirSL it allow some forms of ADny to bediagnoSed raPdly even in the absenee of a family history. Second. it talses the POssibilitythat specific phenotws wilI be associated with severai of the mutahons, so that muchmore aocurate and timly counsling can be PrOvide tO be Patients. The it isPOssible that, by correlation of specific mutaions with the clinical PhenotyPe, some cluesto the Pathogenic mechasm of the disease will be fOuIul that wll eventually alIow thecourse of the disease to be aitered.