色觉的分子基础

视觉的一个重要功能是对颜色的分辨。60年代以来,对色觉的研究已取得许多进展,Young-Helmholtz三色理论的细胞基础已经奠定。应用眼底反射术在人的视盲膜已鉴定了三种视锥(细胞)色素,即红敏、绿敏、蓝敏色素;并证明红色盲者缺少红色素,绿色盲者缺少绿色素。微分光光度术分析表明。

Color Vision Defects with Variation in the Exon 5 of Red and Green Pigment Genes

Purpose : To investigate correlation of variation in the exon 5 of red and green pigment genes with color vision defects.Methods : Exon 5 of the red and green pigment genes in 11 protans, 19 deutans and 38 normal controls were analyzed by heteroduplux-SSCP analysis.Results : In all 11 protans and 8 of the 19 deutans, defects of the red or green pigment gene could be identified. The C polymorphism (A/C at codon 283) in green pigment gene was present in 8 of 44 trichromats and 5 of 24 dichromats. Specific electrophoretic bands were found in 2 normal controls and a deutan.Conclusions: Variation in the exon 5 of the red and green pigment genes is the most common cause for color vision defects. Heteroduplex-SSCP analysis is a suitable way in screening specific variation in visual pigment genes. Eye Science 1998; 14 : 130 - 133.

A COMPLETE SCREEN FOR MUTATIONS OF THE RHODOPSIN GENE IN A PANEL OF CHINESE PATIENTS WITH AUTOSOMAL DOMINANT RETINITIS PIGMENTOSA

Objective To evaluate the prevalence of rhodopsin (RHO) mutations and the genotype-phenotype relationships in Chinese patients with autosomal dominant retinitis pigmentosa (ADRP) by conformation sensitive gel electrophoresis (CSGE) and direct DNA sequencing. Methods We have screened the five coding exons and splice sites of RHO gene in 27 probands who had no relativity from Chinese ADRP families and 100 normal controls to identify disease-associated mutations, using CSGE and direct DNA sequencing. Family members of some probands with disease-associated mutations were also genotyped to determine whether the RHO mutations segregated with retinitis pigmentosa (RP) in their families. Results Two RHO mutations, Pro347Leu and Pro327 (1-bp del), were identified separately in two families, thus the frequency of RHO mutations among this set of Chinese ADRP families is about 7.4% (2/27). Pro347Leu mutation was found in one ADRP proband as well as three her children who also had RP. She had relatively early onset at about 17 years. The only one child without this mutation had no symptom or sign of RP at age of 34. Pro327 (1-bp del) was identified in a late-onset ADRP patient, who appeared night blindness around 30 years old and in her fifties electroretinogram (ERG) has been flat in both scotopic and photopic phases. Family analysis showed that this mutation also existed in her younger dau-ghter and her elder sister, both of them also had RP. Three other family members were genotypically and phenotypically normal. Neither of the two mutations was detected in 100 normal controls.Conclusions The frequency of RHO mutations in Chinese patients was lower than that in Europe and North America. The phenotype of the patients with Pro347Leu corresponded to type 1 ADRP, with severe rod degeneration and some cone preservation later, while the phenotype of the patients carrying Pro327 (1-bp del) corresponded to type 2 ADRP, with a concomitant loss of rod and cone visual function. CSGE was found to be a sensitive, simple, and practical method for the screening of a large number of samples under highly reproducible conditions, and could be utilized in routine molecular diagnostic laboratories.

Mass genetics study of rhodopsin point mutations in retinitis pigmentosa

Objective: To evaluate the incidence and pattern of rhodopsin (RHO) mutations in Chinese patients with retinitis pigmentosa (RP). Methods: Conformation sensitive gel electrophoresis (CSGE) and direct DNA sequencing were applied to detect point mutations that occurred in the five coding exons and splice sites of RHO gene in 98 index patients with RP. Results: Four patients of one ADRP family were found to have a missense mutation at codon 347, Pro347Leu. One late-onset RP patient and her daughter, without clinical expression at present, were discovered to have a novel frameshift mutation at codon 327, Pro327 (1-bp del) . Neither of the two mutations was found in 100 normal controls. Ala299Ser was found in one RP patient. Two control subjects also had Ala299Ser, suggesting its nonpathogenicity and just single nucleotide polymorphism (SNP). Conclusion: Two RP patients had rhodopsin mutations, thus the expected frequency of RHO mutations in RP is about 2.0% (95% confidence interval: 0.3%-4.4%). A highly conserved C-terminal sequence QVS(A) PA was altered due to Pro347Leu and thereby misdirecting rhodopsin to incorrect subcellular location. Loss of all phosphory-lation sites at the C-terminus and a highly conserved sequence QVS(A)PA may occur because of Pro327(1-bp del) . To elucidate the predominant biochemical defects in such mutant, transgenic mice and transfected culture cells carrying Pro327(1-bp del) would be of great value.

Two novel mutations of the retinitis pigmentosa GTPase regulator gene in two Chinese families with X-linked retinitis pigmentosa

Objective To detect mutations of the retinitis pigmentosa GTPase regulator (RPGR) gene in two Chinese X-linked retinitis pigmentosa families. Methods Fragments of exons 1-19 of the RPGR gene were amplified with intronic primers, using genomic DNA as template. The polymerase chain reaction (PCR) products were analysed by single-strand conformation polymorphism (SSCP) and direct sequencing. Mutations were identified by comparing DNA sequences of the patients with those of the normal controls.Results Two novel mutations, c1536delC and E332X, were identified in exons 12 and 9 of the RPGR gene in both families. Each mutation was the first mutation found in their respective exons. Both mutations were predicted to cause premature termination, which resulted in truncated proteins without normal functions of the RPGR products.Conclusions Both mutations are the genetic basis of the pathogenesis in the respective families. Our data might be helpful in analysing the function of the RPGR protein.

Generation of nonhuman primate retinitis pigmentosa model by in situ knockout of RHO in rhesus macaque retina

Retinitis pigmentosa(RP)is a form of inherited retinal degenerative diseases that ultimately involves the macula,which is present in primates but not in the rodents.Therefore,creating nonhuman primate(NHP)models of RP is of critical importance to study its mechanism of pathogenesis and to evaluate potential therapeutic options in the future.Here we applied adeno-associated virus(AAV)-delivered CRISPR/SaCas9 technology to knockout the RHO gene in the retinae of the adult rhesus macaque(Macaca mulatta)to investigate the hypothesis whether non-germline mutation of the RHO gene is sufficient to recapitulate RP.Through a series of studies,we were able to demonstrate successful somatic editing of the RHO gene and reduced RHO protein expression.More importantly,the mutant macaque retinae displayed clinical RP phenotypes,including photoreceptor degeneration,retinal thinning,abnormal rod subcellular structures,and reduced photoresponse.Therefore,we suggest somatic editing of the RHO gene is able to phenocopy RP,and the reduced time span in generating NHP mutant accelerates RP research and expands the utility of NHP model for human disease study.