retinaldehyde and Retinitis-Pigmentosa

RPE65 isomerase, expressed in the retinal pigmented epithelium (RPE), is an enzymatic component of the retinoid cycle, converting all-trans retinyl ester into 11-cis retinol, and it is essential for vision, because it replenishes the photon capturing 11-cis retinal. To date, almost 200 loss-of-function mutations have been identified within the

Topics: Age of Onset; Amino Acid Substitution; Animals; Choroideremia; cis-trans-Isomerases; Clinical Trials, Phase I as Topic; DNA, Complementary; Enzyme Replacement Therapy; Female; Gene Knock-In Techniques; Genes, Dominant; Genetic Therapy; Genetic Vectors; Humans; Leber Congenital Amaurosis; Male; Mice; Mutation, Missense; Pedigree; Point Mutation; Proof of Concept Study; Protein Isoforms; Retinaldehyde; Retinitis Pigmentosa

Mutations in rhodopsin are one of the most common causes of retinitis pigmentosa (RP). Misfolding of rhodopsin can result in disruptions in cellular protein homeostasis, or proteostasis. There is currently no available treatment for RP. In this review, we discuss the different approaches currently being investigated for treatment of rhodopsin RP, focusing on the potential of manipulation of the proteostasis network as a therapeutic approach to combat retinal degeneration.

Topics: Animals; Disease Models, Animal; Genetic Predisposition to Disease; Humans; Molecular Targeted Therapy; Mutation; Proteostasis Deficiencies; Retinaldehyde; Retinitis Pigmentosa; Rhodopsin

Several pathogenic variants have been reported in the

Topics: Animals; Extracellular Matrix; Extracellular Matrix Proteins; Eye Proteins; Mice; Photoreceptor Cells; Proteoglycans; Retinal Pigment Epithelium; Retinal Pigments; Retinaldehyde; Retinitis Pigmentosa; Vitelliform Macular Dystrophy

The largest class of rhodopsin mutations causing autosomal dominant retinitis pigmentosa (adRP) is mutations that lead to misfolding and aggregation of the receptor. The misfolding mutants have been characterized biochemically, and categorized as either partial or complete misfolding mutants. This classification is incomplete and does not provide sufficient information to fully understand the disease pathogenesis and evaluate therapeutic strategies. A Förster resonance energy transfer (FRET) method was utilized to directly assess the aggregation properties of misfolding rhodopsin mutants within the cell. Partial (P23H and P267L) and complete (G188R, H211P, and P267R) misfolding mutants were characterized to reveal variability in aggregation properties. The complete misfolding mutants all behaved similarly, forming aggregates when expressed alone, minimally interacting with the wild-type receptor when coexpressed, and were unresponsive to treatment with the pharmacological chaperone 9-cis retinal. In contrast, variability was observed between the partial misfolding mutants. In the opsin form, the P23H mutant behaved similarly as the complete misfolding mutants. In contrast, the opsin form of the P267L mutant existed as both aggregates and oligomers when expressed alone and formed mostly oligomers with the wild-type receptor when coexpressed. The partial misfolding mutants both reacted similarly to the pharmacological chaperone 9-cis retinal, displaying improved folding and oligomerization when expressed alone but aggregating with wild-type receptor when coexpressed. The observed differences in aggregation properties and effect of 9-cis retinal predict different outcomes in disease pathophysiology and suggest that retinoid-based chaperones will be ineffective or even detrimental.

Topics: Diterpenes; Fluorescence Resonance Energy Transfer; HEK293 Cells; Humans; Molecular Chaperones; Mutation; Protein Aggregation, Pathological; Protein Folding; Recombinant Proteins; Retinaldehyde; Retinitis Pigmentosa; Rhodopsin

Although several genetic and biochemical factors are associated with the pathogenesis of retinal degeneration, it has yet to be determined how these different impairments can cause similar degenerative phenotypes. Here, we report microglial/macrophage activation in both a Stargardt disease and age-related macular degeneration mouse model caused by delayed clearance of all-trans-retinal from the retina, and in a retinitis pigmentosa mouse model with impaired retinal pigment epithelium (RPE) phagocytosis. Mouse microglia displayed RPE cytotoxicity and increased production of inflammatory chemokines/cytokines, Ccl2, Il1b, and Tnf, after coincubation with ligands that activate innate immunity. Notably, phagocytosis of photoreceptor proteins increased the activation of microglia/macrophages and RPE cells isolated from model mice as well as wild-type mice. The mRNA levels of Tlr2 and Tlr4, which can recognize proteins as their ligands, were elevated in mice with retinal degeneration. Bone marrow-derived macrophages from Tlr4-deficient mice did not increase Ccl2 after coincubation with photoreceptor proteins. Tlr4(-/-)Abca4(-/-)Rdh8(-/-) mice displayed milder retinal degenerative phenotypes than Abca4(-/-)Rdh8(-/-) mice. Additionally, inactivation of microglia/macrophages by pharmacological approaches attenuated mouse retinal degeneration. This study demonstrates an important contribution of TLR4-mediated microglial activation by endogenous photoreceptor proteins in retinal inflammation that aggravates retinal cell death. This pathway is likely to represent an underlying common pathology in degenerative retinal disorders.

Topics: Animals; Chemokine CCL2; Eye Proteins; Interleukin-1beta; Macular Degeneration; Mice; Mice, Knockout; Microglia; Photoreceptor Cells, Vertebrate; Retinaldehyde; Retinitis Pigmentosa; Toll-Like Receptor 4; Tumor Necrosis Factor-alpha

Autosomal dominant retinitis pigmentosa (ADRP) mutants (T4K, N15S, T17M, V20G, P23A/H/L, and Q28H) in the N-terminal cap of rhodopsin misfold when expressed in mammalian cells. To gain insight into the causes of misfolding and to define the contributions of specific residues to receptor stability and function, we evaluated the responses of these mutants to 11-cis-retinal pharmacological chaperone rescue or disulfide bond-mediated repair. Pharmacological rescue restored folding in all mutants, but the purified mutant pigments in all cases were thermo-unstable and exhibited abnormal photobleaching, metarhodopsin II decay, and G protein activation. As a complementary approach, we superimposed this panel of ADRP mutants onto a rhodopsin background containing a juxtaposed cysteine pair (N2C/D282C) that forms a disulfide bond. This approach restored folding in T4K, N15S, V20G, P23A, and Q28H but not T17M, P23H, or P23L. ADRP mutant pigments obtained by disulfide bond repair exhibited enhanced stability, and some also displayed markedly improved photobleaching and signal transduction properties. Our major conclusion is that the N-terminal cap stabilizes opsin during biosynthesis and contributes to the dark-state stability of rhodopsin. Comparison of these two restorative approaches revealed that the correct position of the cap relative to the extracellular loops is also required for optimal photochemistry and efficient G protein activation.

Topics: Amino Acid Substitution; Animals; Cattle; HEK293 Cells; Humans; Mutation, Missense; Protein Folding; Protein Stability; Protein Structure, Secondary; Protein Structure, Tertiary; Retinaldehyde; Retinitis Pigmentosa; Rhodopsin

Retinitis pigmentosa (RP) is a pathological condition associated with blindness due to progressive retinal degeneration. RP-linked mutations lead to changes at the retinal binding pocket and in the absorption spectra. Here, we evaluate the geometries, electronic effects, and vertical excitation energies in the dark state of mutated human rhodopsins carrying the abnormal substitutions M207R or S186W at the retinal binding pocket. Two models are used, the solvated protein and the protein in a solvated POPC lipid bilayer. We apply homology modeling, classical molecular dynamics simulations, density functional theory (DFT), and quantum mechanical/molecular mechanical (QM/MM) methods. Our results for the wild type bovine and human rhodopsins, used as a reference, are in good agreement with experiment. For the mutants, we find less twisted QM/MM ground-state chromophore geometries around the C(11)-C(12) double bond and substantial blue shifts in the lowest vertical DFT excitation energies. An analysis of the QM energies shows that the chromophore-counterion region is less stable in the mutants compared to the wild type, consistent with recent protein folding studies. The influence of the mutations near the chromophore is discussed in detail to gain more insight into the properties of these mutants. The spectral tuning is mainly associated with counterion effects and structural features of the retinal chain in the case of the hM207R mutant, and with the presence of a neutral chromophore with deprotonated Lys296 in the case of the hS186W mutant.

Topics: Animals; Binding Sites; Cattle; Crystallography, X-Ray; Humans; Lipid Bilayers; Models, Molecular; Molecular Dynamics Simulation; Molecular Sequence Data; Molecular Structure; Mutation; Protein Conformation; Quantum Theory; Retinaldehyde; Retinitis Pigmentosa; Rhodopsin

Two different mutations at Gly-90 in the second transmembrane helix of the photoreceptor protein rhodopsin have been proposed to lead to different phenotypes. G90D has been classically associated with congenital night blindness, whereas the newly reported G90V substitution was linked to a retinitis pigmentosa phenotype. Here, we used Val/Asp replacements of the native Gly at position 90 to unravel the structure/function divergences caused by these mutations and the potential molecular mechanisms of inherited retinal disease. The G90V and G90D mutants have a similar conformation around the Schiff base linkage region in the dark state and same regeneration kinetics with 11-cis-retinal, but G90V has dramatically reduced thermal stability when compared with the G90D mutant rhodopsin. The G90V mutant also shows, like G90D, an altered photobleaching pattern and capacity to activate Gt in the opsin state. Furthermore, the regeneration of the G90V mutant with 9-cis-retinal was improved, achieving the same A(280)/A(500) as wild type isorhodopsin. Hydroxylamine resistance was also recovered, indicating a compact structure around the Schiff base linkage, and the thermal stability was substantially improved when compared with the 11-cis-regenerated mutant. These results support the role of thermal instability and/or abnormal photoproduct formation in eliciting a retinitis pigmentosa phenotype. The improved stability and more compact structure of the G90V mutant when it was regenerated with 9-cis-retinal brings about the possibility that this isomer or other modified retinoid analogues might be used in potential treatment strategies for mutants showing the same structural features.

Topics: Amino Acid Substitution; Animals; Cattle; Cell Line, Tumor; COS Cells; Diterpenes; Eye Diseases, Hereditary; Genetic Diseases, X-Linked; Humans; Mutation, Missense; Myopia; Night Blindness; Protein Stability; Protein Structure, Tertiary; Retinaldehyde; Retinitis Pigmentosa; Rhodopsin; Structure-Activity Relationship

Variants of rhodopsin, a complex of 11-cis retinal and opsin, cause retinitis pigmentosa (RP), a degenerative disease of the retina. Trafficking defects due to rhodopsin misfolding have been proposed as the most likely basis of the disease, but other potentially overlapping mechanisms may also apply. Pharmacological therapies for RP must target the major disease mechanism and contend with overlap, if it occurs. To this end, we have explored the molecular basis of rhodopsin RP in the context of pharmacological rescue with 11-cis retinal. Stable inducible cell lines were constructed to express wild-type opsin; the pathogenic variants T4R, T17M, P23A, P23H, P23L, and C110Y; or the nonpathogenic variants F220L and A299S. Pharmacological rescue was measured as the fold increase in rhodopsin or opsin levels upon addition of 11-cis retinal during opsin expression. Only Pro23 and T17M variants were rescued significantly. C110Y opsin was produced at low levels and did not yield rhodopsin, whereas the T4R, F220L, and A299S proteins reached near-wild-type levels and changed little with 11-cis retinal. All of the mutant rhodopsins exhibited misfolding, which increased over a broad range in the order F220L, A299S, T4R, T17M, P23A, P23H, P23L, as determined by decreased thermal stability in the dark and increased hydroxylamine sensitivity. Pharmacological rescue increased as misfolding decreased, but was limited for the least misfolded variants. Significantly, pathogenic variants also showed abnormal photobleaching behavior, including an increased ratio of metarhodopsin-I-like species to metarhodopsin-II-like species and aberrant photoproduct accumulation with prolonged illumination. These results, combined with an analysis of published biochemical and clinical studies, suggest that many rhodopsin variants cause disease by affecting both biosynthesis and photoactivity. We conclude that pharmacological rescue is promising as a broadly effective therapy for rhodopsin RP, particularly if implemented in a way that minimizes the photoactivity of the mutant proteins.

Topics: Amino Acid Substitution; Animals; Base Sequence; Cattle; Cell Line; DNA Primers; Genetic Variation; Humans; Hydroxylamine; In Vitro Techniques; Mutant Proteins; Mutation; Opsins; Photobleaching; Protein Folding; Protein Stability; Recombinant Proteins; Retinaldehyde; Retinitis Pigmentosa; Rhodopsin

To assess the safety and to quantify the effects of a single application of all-trans-N-retinylacetamide on the rat retina measured by electroretinography (ERG). Brown Norway rats were assigned to either a control group (n = 13) or to one of the three groups treated with a single intra-peritoneal dose of all-trans-N-retinylacetamide: 20 (n = 8), 5 (n = 7), or 1 mg/kg (n = 8). Full-field ERGs were performed 7 days before (baseline) and 12 h after treatment. Intensity-response relationship of b-wave amplitudes were evaluated in dark-adapted conditions using white stimuli (0.000003-0.3 cd.s/m(2)). Fast dynamics of rod sensitivity was assessed by a paired-flash paradigm; recovery dynamics of b-wave amplitudes after bleaching was followed for 70 min. Light-adapted ERGs were recorded for cone evaluation. No effects were found on either dark-adapted sensitivity or on fast rod recovery. However, drug treatment at 5 and 20 mg/kg significantly delayed ERG amplitude recovery after bleaching: 60 min after bleaching the b-wave amplitude was 21 + or - 9% (P < 0.05) and 66 + or - 10% (P < 0.05), respectively, compared to baseline. Recovery rates returned to normal 8 weeks after treatment. There were no changes in light-adapted ERG in any group. Systemic administration of a single dose of the visual cycle modulator all-trans-N-retinylacetamide reversibly delayed recovery of dark-adapted ERG amplitudes after bleaching, leaving other functions unchanged. This finding could make the compound potentially useful in experimental conditions or in specific diseases where the visual cycle is involved, such as retinitis pigmentosa or age-related macular degeneration.

Topics: Animals; Dark Adaptation; Dose-Response Relationship, Drug; Electroretinography; Female; Humans; Injections, Intraperitoneal; Macular Degeneration; Rats; Rats, Inbred BN; Retina; Retinaldehyde; Retinitis Pigmentosa; Retinoids; Time Factors; Visual Pathways

The lectin chaperone calnexin (Cnx) is important for quality control of glycoproteins, and the chances of correct folding of a protein increase the longer the protein interacts with Cnx. Mutations in glycoproteins increase their association with Cnx, and these mutant proteins are retained in the endoplasmic reticulum. However, until now, the increased interaction with Cnx was not known to increase the folding of mutant glycoproteins. Because many human diseases result from glycoprotein misfolding, a Cnx-assisted folding of mutant glycoproteins could be beneficial. Mutations of rhodopsin, the glycoprotein pigment of rod photoreceptors, cause misfolding resulting in retinitis pigmentosa. Despite the critical role of Cnx in glycoprotein folding, surprisingly little is known about its interaction with rhodopsin or whether this interaction could be modulated to increase the folding of mutant rhodopsin. Here, we demonstrate that Cnx preferentially associates with misfolded mutant opsins associated with retinitis pigmentosa. Furthermore, the overexpression of Cnx leads to an increased accumulation of misfolded P23H opsin but not the correctly folded protein. Finally, we demonstrate that increased levels of Cnx in the presence of the pharmacological chaperone 11-cis-retinal increase the folding efficiency and result in an increase in correct folding of mutant rhodopsin. These results demonstrate that misfolded rather than correctly folded rhodopsin is a substrate for Cnx and that the interaction between Cnx and mutant, misfolded rhodopsin, can be targeted to increase the yield of folded mutant protein.

Topics: Animals; Blotting, Western; Calnexin; Cell Line; Endoplasmic Reticulum; Humans; Immunoprecipitation; Mice; Mice, Inbred C57BL; Mutant Proteins; Mutation; Protein Binding; Protein Folding; Retinaldehyde; Retinitis Pigmentosa; Rhodopsin

The visual (retinoid) cycle is a fundamental metabolic process in vertebrate retina responsible for production of 11-cis-retinal, the chromophore of rhodopsin and cone pigments. 11-cis-Retinal is bound to opsins, forming visual pigments, and when the resulting visual chromophore 11-cis-retinylidene is photoisomerized to all-trans-retinylidene, all-trans-retinal is released from these receptors. Toxic byproducts of the visual cycle formed from all-trans-retinal often are associated with lipofuscin deposits in the retinal pigmented epithelium (RPE), but it is not clear whether aberrant reactions of the visual cycle participate in RPE atrophy, leading to a rapid onset of retinopathy. Here we report that mice lacking both the ATP-binding cassette transporter 4 (Abca4) and enzyme retinol dehydrogenase 8 (Rdh8), proteins critical for all-trans-retinal clearance from photoreceptors, developed severe RPE/photoreceptor dystrophy at an early age. This phenotype includes lipofuscin, drusen, and basal laminar deposits, Bruch's membrane thickening, and choroidal neovascularization. Importantly, the severity of visual dysfunction and retinopathy was exacerbated by light but attenuated by treatment with retinylamine, a visual cycle inhibitor that slows the flow of all-trans-retinal through the visual cycle. These findings provide direct evidence that aberrant production of toxic condensation byproducts of the visual cycle in mice can lead to rapid, progressive retinal degeneration.

Topics: Alcohol Oxidoreductases; Animals; ATP-Binding Cassette Transporters; Bruch Membrane; Lipofuscin; Mice; Mice, Knockout; Pigment Epithelium of Eye; Retinal Cone Photoreceptor Cells; Retinal Drusen; Retinaldehyde; Retinitis Pigmentosa; Rhodopsin; Vision, Ocular

To elucidate the molecular mechanisms underlying the light-sensitive retinal degeneration caused by the rhodopsin mutation P23H, which causes retinitis pigmentosa (RP) in humans, we expressed Xenopus laevis, bovine, human, and murine forms of P23H rhodopsin in transgenic X. laevis rod photoreceptors. All P23H rhodopsins caused aggressive retinal degeneration associated with low expression levels and retention of P23H rhodopsin in the endoplasmic reticulum (ER), suggesting involvement of protein misfolding and ER stress. However, light sensitivity varied dramatically between these RP models, with complete or partial rescue by dark rearing in the case of bovine and human P23H rhodopsin, and no rescue for X. laevis P23H rhodopsin. Rescue by dark rearing required an intact 11-cis-retinal chromophore binding site within the mutant protein and was associated with truncation of the P23H rhodopsin N terminus. This yielded an abundant nontoxic approximately 27 kDa form that escaped the ER and was transported to the rod outer segment. The truncated protein was produced in the greatest quantities in dark-reared retinas expressing bovine P23H rhodopsin and was not observed with X. laevis P23H rhodopsin. These results are consistent with a mechanism involving enhanced protein folding in the presence of 11-cis-retinal chromophore, with ER exit assisted by proteolytic truncation of the N terminus. This study provides a molecular mechanism for light sensitivity observed in other transgenic models of RP and for phenotypic variation among RP patients.

Topics: Animals; Animals, Genetically Modified; Cattle; Cell Line, Transformed; Darkness; Disease Models, Animal; Gene Expression Regulation; Histidine; Humans; Mice; Microscopy, Electron, Scanning; Mutation; Peptide Fragments; Proline; Retinal Rod Photoreceptor Cells; Retinaldehyde; Retinitis Pigmentosa; Rhodopsin; Transfection; Xenopus laevis

Retinitis pigmentosa (RP) is a heterogeneous group of hereditary disorders of the retina caused by mutation in genes of the photoreceptor proteins with an autosomal dominant (adRP), autosomal recessive (arRP), or X-linked pattern of inheritance. Although there are over 100 identified mutations in the opsin gene associated with RP, only a few of them are inherited with the arRP pattern. E150K is the first reported missense mutation associated with arRP. This opsin mutation is located in the second cytoplasmic loop of this G protein-coupled receptor. E150K opsin expressed in HEK293 cells and reconstituted with 11-cis-retinal displayed an absorption spectrum similar to the wild type (WT) counterpart and activated G protein transducin slightly faster than WT receptor. However, the majority of E150K opsin showed a higher apparent molecular mass in SDS-PAGE and was resistant to endoglycosidase H deglycosidase. Instead of being transported to the plasma membrane, E150K opsin is partially colocalized with the cis/medial Golgi compartment markers such as GM130 and Vti1b but not with the trans-Golgi network. In contrast to the endoplasmic reticulum-retained adRP mutant, P23H opsin, Golgi-retained E150K opsin did not influence the proper transport of the WT opsin when coexpressed in HEK293 cells. This result is consistent with the recessive pattern of inheritance of this mutation. Thus, our study reveals a novel molecular mechanism for retinal degeneration that results from deficient export of opsin from the Golgi apparatus.

Topics: Cell Line; Genes, Recessive; Golgi Apparatus; Humans; Mutation, Missense; Protein Transport; Retinal Degeneration; Retinaldehyde; Retinitis Pigmentosa; Rod Opsins; Transfection

To report a novel mutation in the RLBP1 gene and optical coherence tomographic findings in a Japanese patient with retinitis punctata albescens.. Observational case report.. The RLBP1 gene was analyzed by direct genomic sequencing. A complete ophthalmologic examination was performed.. Compound heterozygous mutations in the RLBP1 gene were identified in the patient. The mutations were a novel missense Arg103Trp mutation and a missense Arg234Trp mutation, the causative mutation of Bothnia dystrophy. The patient's fundi showed numerous white dots with diffuse retinal mottling and bilateral macular degeneration. Her visual function deteriorated progressively during 12-year follow-up. Optical coherence tomography demonstrated decreased retinal thickness, especially the photoreceptor layer.. A novel mutation in RLBP1 gene was found in a Japanese patient with retinitis punctata albescens. Degenerative changes of the outer retina were detected by optical coherence tomography.

Topics: Adolescent; Carrier Proteins; Electrooculography; Female; Fluorescein Angiography; Humans; Mutation, Missense; Night Blindness; Point Mutation; Retina; Retinaldehyde; Retinitis Pigmentosa; Tomography, Optical Coherence; Visual Acuity

To evaluate the molecular genetic defects associated with retinitis punctata albescens (RPA) in 5 patients from 3 families with this disease.. We examined 3 probands and 2 clinically affected relatives with RPA. Clinical examinations included best-corrected visual acuity, visual field testing, electroretinography, dilated fundus examination, and fundus photography. Leukocyte DNA was analyzed for mutations in the exons of the genes encoding cellular retinaldehyde-binding protein 1 (RLBP1), 11-cis-retinol dehydrogenase (RDH5), interphotoreceptor retinoid-binding protein (RBP3), and photoreceptor all-trans-retinol dehydrogenase (RDH8). Not all patients were evaluated for mutations in each gene. The exons were individually amplified and screened for mutations by single-stranded conformational polymorphism analysis or direct genomic sequencing.. The 3 probands had similar clinical findings, including a history of poor night vision, the presence of punctate white deposits in the retina, and substantially reduced or absent rod responses on electroretinogram testing. One of the probands (patient 2:III:2) had 2 novel mutations in the RLBP1 gene (Arg151Trp and Gly31[2-base pair deletion], [GGA-->G-]). Segregation analysis showed that the 2 mutations were allelic and that the patient was a compound heterozygote. Both parents of the proband manifested round white deposits in the retina. The other 2 probands had no detected pathogenic mutations in RLBP1 or in the other 3 genes evaluated.. The identification of novel RLBP1 mutations in 1 of our 3 probands, all with RPA, is further evidence of genetic (nonallelic) heterogeneity in this disease. The presence of round white deposits in the retina may be observed in those heterozygous for RLBP1. Clinical Relevance Patients with a clinical presentation of RPA can have genetically different mutations. Drusen-like lesions may be observed in heterozygotes in families with this disease and a mutation in RLBP1.

Topics: Adult; Carrier Proteins; Child; DNA Mutational Analysis; Electroretinography; Female; Fundus Oculi; Genetic Heterogeneity; Heterozygote; Humans; Male; Middle Aged; Mutation; Night Blindness; Pedigree; Retina; Retinaldehyde; Retinitis Pigmentosa; Visual Acuity; Visual Fields

To describe a patient with retinitis punctata albescens (RPA) associated with compound heterozygosity for two novel mutations in the RLBP1 encoding cellular retinaldehyde-binding protein (CRALBP).. Observational case report.. The proband underwent a complete ophthalmic examination and leukocyte genomic DNA samples were obtained from him and his parents. The RLBP1 exons were analyzed by direct sequencing of PCR-amplified fragments.. The patient had a clinical phenotype suggestive of slowly progressive RPA, characterized by numerous yellow-white dots in the fundus. The RLBP1 sequence analysis revealed a novel compound heterozygotic mutation of Gly145Asp and Ile200Thr transmitted from the mother and father, respectively. Analysis of 100 control chromosomes showed no individuals with these sequence alterations.. Only eight RLBP1 mutations have been reported to date, and here we describe two novel mutations. These additional mutations will aid ongoing functional studies and add to our understanding of the molecular pathology pertaining to RLBP1-associated retinopathies.

Topics: Adolescent; Carrier Proteins; DNA Mutational Analysis; Genetic Heterogeneity; Heterozygote; Humans; Male; Mutation; Night Blindness; Pedigree; Polymerase Chain Reaction; Retinaldehyde; Retinitis Pigmentosa

Changes induced by mutations in rhodopsin that are associated with the degenerative visual disease retinitis pigmentosa result in an altered pattern of light absorption according to quantum mechanical simulations and reference experimental works. Eleven single-point mutations associated with retinitis pigmentosa at and in the proximity to the retinal binding pocket of rhodopsin have been modeled in silico and their spectra calculated with the NDOL (Neglect of Differential Overlap accounting L azimuthal quantum number) a priori method. The altered pattern of absorption found would lead to cumulative consequences in energy dissipation with aging. Different energy balances in the case of mutants at the very molecular level, compared to native nonmutated rhodopsin, can cause permanent cellular stress and would play a role in the progression of the retine degenerative process. It could explain the worsening of the pathological condition mostly in adults and suggests the probable beneficial effects of using quenching drugs and protection devices against excess of light in the early stages of life for avoiding or reducing potential damage.

Topics: Absorption; Amino Acid Sequence; Computational Biology; Humans; Isomerism; Light; Models, Structural; Molecular Sequence Data; Point Mutation; Predictive Value of Tests; Retina; Retinaldehyde; Retinitis Pigmentosa; Rhodopsin; Spectrum Analysis; Ultraviolet Rays

This work is part of a feasibility assessment of a retinal prosthesis as a means to restore vision to patients with blindness caused by retinitis pigmentosa. The primary goal was to assess the concordance of the form of induced perception and the pattern of electrical stimulation of the retina, and the reproducibility of the responses.. Five volunteers with severe retinitis pigmentosa and one with normal vision were studied. A companion paper in this issue provides details on demographics, visual function, surgical methods, general stimulation strategy, and data analysis. Volunteers were awake during surgery while a 10-microm-thick, microfabricated electrode array was placed on the retina. The array was connected to extraocular current sources that delivered charges to 50-, 100-, and 400-microm-diameter electrodes. Negative control trials were randomly included. Perceptual quality was judged by the similarity between the form of stimulation and perception (i.e., accuracy) and the reproducibility of responses.. Only 1 of 40 control tests yielded a false-positive result. On average, volunteers 3, 5, and 6 reported percepts that matched the stimulation pattern 48% and 32% of the time for single- and multiple-electrode trials, respectively. Two-point discrimination in the best cases may have been achieved in two blind subjects using (center-to-center) electrode separation of 600 and 1960 microm. Reproducibility was achieved 66% of the time in the blind subjects. By comparison, in the normal-sighted subject, perceptual form was reported accurately 57% of the time, with 82% reproducibility, and two-point discrimination may have been achieved in one trial with 620-microm electrode spacing and in two trials each with 1860- and 2480-microm electrode spacing. In subjects 5 and 6, perceptual size was inconsistently related to the charge, although relatively large differences in charge (median: 0.55 microcoulombs [microC]) between two trials produced differently sized percepts. Longer stimuli did not produce rounder percepts.. Single percepts induced by single-electrode stimulation were relatively small, but the form of percepts, especially after multielectrode stimulation, often did not match the stimulation pattern, even in a normal-sighted volunteer. Reproducible percepts were more easily generated than those that matched the stimulation pattern.

Topics: Adult; Aged; Blindness; Electric Stimulation; False Positive Reactions; Female; Humans; Male; Microelectrodes; Middle Aged; Predictive Value of Tests; Reproducibility of Results; Retinaldehyde; Retinitis Pigmentosa; Sensory Thresholds; Visual Perception

Mutations in the photopigment rhodopsin are the major cause of autosomal dominant retinitis pigmentosa. The majority of mutations in rhodopsin lead to misfolding of the protein. Through the detailed examination of P23H and K296E mutant opsin processing in COS-7 cells, we have shown that the mutant protein does not accumulate in the Golgi, as previously thought, instead it forms aggregates that have many of the characteristic features of an aggresome. The aggregates form close to the centrosome and lead to the dispersal of the Golgi apparatus. Furthermore, these aggregates are ubiquitinated, recruit cellular chaperones and disrupt the intermediate filament network. Mutant opsin expression can disrupt the processing of normal opsin, as co-transfection revealed that the wild-type protein is recruited to mutant opsin aggregates. The degradation of mutant opsin is dependent on the proteasome machinery. Unlike the situation with DeltaF508-CFTR, proteasome inhibition does not lead to a marked increase in aggresome formation but increases the retention of the protein within the ER, suggesting that the proteasome is required for the efficient retrotranslocation of the mutant protein. Inhibition of N-linked glycosylation with tunicamycin leads to the selective retention of the mutant protein within the ER and increases the steady state level of mutant opsin. Glycosylation, however, has no influence on the biogenesis and targeting of wild-type opsin in cultured cells. This demonstrates that N-linked glycosylation is required for ER-associated degradation of the mutant protein but is not essential for the quality control of opsin folding. The addition of 9-cis-retinal to the media increased the amount of P23H, but not K296E, that was soluble and reached the plasma membrane. These data show that rhodopsin autosomal dominant retinitis pigmentosa is similar to many other neurodegenerative diseases in which the formation of intracellular protein aggregates is central to disease pathogenesis, and they suggest a mechanism for disease dominance.

Topics: Animals; Cell Membrane; COS Cells; Cysteine Endopeptidases; Diterpenes; Eukaryotic Cells; Glycosylation; Golgi Apparatus; Inclusion Bodies; Microscopy, Electron; Molecular Chaperones; Multienzyme Complexes; Mutation; Organelles; Proteasome Endopeptidase Complex; Protein Folding; Protein Transport; Retinaldehyde; Retinitis Pigmentosa; Rhodopsin; Tunicamycin; Ubiquitin

To describe the phenotype of Bothnia dystrophy, an autosomal recessive retinal dystrophy with an R234W mutation in the RLBP1 gene encoding cellular retinaldehyde-binding protein.. Medical records were reviewed retrospectively. Ophthalmologic examination, including kinetic perimetry and, in selected cases, adaptometry, color vision tests, fluorescein angiography, and electrophysiologic studies, was performed. The study included 24 individuals, all homozygous for an R234W mutation in the RLBP1 gene.. Patients typically show night blindness from early childhood. In young adults, retinitis punctata albescens was observed, followed by macular degeneration and a decrease in visual acuity that led to legal blindness in early adulthood. Dark adaptometry and electrophysiologic testing showed an initial loss of rod function followed by a progressive reduction of the cone responses in older ages.. Bothnia dystrophy is a unique retinal dystrophy belonging to the rod-cone dystrophies and has a high prevalence in northern Sweden. Fifty-seven cases of Bothnia dystrophy have been diagnosed, indicating a prevalence as high as 1 per 4500 population in the geographic area studied. A defect ability of mutated cellular retinaldehyde-binding protein to bind retinoid probably explains the defect rod function followed by central and peripheral degeneration.. Retinal dystrophies associated with other mutations of the RLBP1 gene, including retinitis pigmentosa of Bothnia type, might account for a considerable number of cases of autosomal recessive retinitis pigmentosa in other geographic areas as well.

Topics: Adolescent; Adult; Aged; Carrier Proteins; Child; Electrophysiology; Female; Fluorescein Angiography; Humans; Male; Middle Aged; Phenotype; Photoreceptor Cells, Vertebrate; Point Mutation; Retinaldehyde; Retinitis Pigmentosa; Retrospective Studies; Sweden; Visual Acuity; Visual Fields

ABCR is a photoreceptor-specific ATP-binding cassette transporter that has been linked to various retinal diseases, including Stargardt macular dystrophy, and implicated in retinal transport across rod outer segment (ROS) membranes. We have examined the ATPase and GTPase activity of detergent-solubilized and reconstituted ABCR. 3-[(3-Cholamidopropyl)dimethylammonio]-1-propanesulfonic acid-solubilized ABCR had ATPase and GTPase activity (K(m) approximately 75 micrometer V(max) approximately 200 nmol/min/mg) that was stimulated 1.5-2-fold by all-trans-retinal and dependent on phospholipid and dithiothreitol. The K(m) for ATP decreased to approximately 25 micrometer after reconstitution, whereas the V(max) was strongly dependent on the lipid used for reconstitution. ABCR reconstituted in ROS phospholipid had a V(max) for basal and retinal activated ATPase activity that was 4-6 times higher than for ABCR in soybean or brain phospholipid. This enhanced activity was mainly due to the high phosphatidylethanolamine (PE) content of ROS membranes. PE was also required for retinoid-stimulated ATPase activity. ATPase activity of ABCR was stimulated by the addition of N-retinylidene-PE but not the reduced derivative, retinyl-PE. ABCR expressed in COS-1 cells also exhibited retinal-stimulated ATPase activity similar to that of the native protein. These results support the view that ABCR is an active retinoid transporter, the nucleotidase activity of which is strongly influenced by its lipid environment.

Topics: Adenosine Triphosphatases; Animals; ATP-Binding Cassette Transporters; Cattle; Cholic Acids; COS Cells; Enzyme Activation; GTP Phosphohydrolases; Humans; Kinetics; Lipids; Phospholipids; Proteolipids; Retinaldehyde; Retinitis Pigmentosa; Retinoids; Rod Cell Outer Segment; Transfection; Vitamin A

To determine the chromosomal location and to identify the gene causing a type of retinitis punctata albescens, called Bothnia dystrophy, found in a restricted geographic area in northern Sweden.. Twenty patients from seven families originating from a restricted geographic area in northern Sweden were clinically examined. Microsatellite markers were analyzed in all affected and unaffected family members. Direct genomic sequencing of the gene encoding cellular retinaldehyde-binding protein was performed after the linkage analysis had been completed.. Affected individuals showed night blindness from early childhood with features consistent with retinitis punctata albescens and macular degeneration. The responsible gene was mapped to 15q26, the same region to which the cellular retinaldehyde-binding protein gene has been assigned. Subsequent analysis showed all affected patients were homozygous for a C to T substitution in exon 7 of the same gene, leading to the missense mutation Arg234Trp. Analysis of marker haplotypes suggested that all cases had a common ancestor who carried the mutation.. A missense mutation in the cellular retinaldehyde-binding protein gene is the cause of Bothnia dystrophy. The disease is a local variant of retinitis punctata albescens that is common in northern Sweden due to a founder mutation.

Topics: Adult; Carrier Proteins; Chromosome Mapping; Chromosomes, Human, Pair 15; DNA; DNA Mutational Analysis; Female; Genetic Linkage; Humans; Male; Microsatellite Repeats; Middle Aged; Mutation, Missense; Night Blindness; Pedigree; Retinaldehyde; Retinitis Pigmentosa; Sweden

To determine the frequency and spectrum of mutations in the RLBP1 gene encoding cellular retinaldehyde-binding protein (CRALBP) in patients with hereditary retinal degeneration.. The single-strand conformation polymorphism (SSCP) technique and a direct genomic sequencing technique were used to screen the coding exons of this gene (exons 2-8) for mutations in 324 unrelated patients with recessive or isolate retinitis pigmentosa, retinitis punctata albescens, Leber congenital amaurosis, or a related disease. Variant DNA fragments revealed by SSCP analysis were subsequently sequenced. Selected alleles that altered the coding region or intron splice sites were evaluated further through segregation analysis in the families of the index cases.. Four novel mutations were identified in this gene among three unrelated patients with recessively inherited retinitis punctata albescens. Two of the mutations were missense: one was a frameshift, and one affected a canonical splice donor site.. Recessive mutations in the RLBP1 gene are an uncommon cause of retinal degeneration in humans. The phenotype produced by RLBP1 mutations seems to be a form of retinitis punctata albescens.

Topics: Adult; Carrier Proteins; DNA; DNA Primers; Female; Frameshift Mutation; Fundus Oculi; Genes, Recessive; Humans; Male; Middle Aged; Mutation, Missense; Night Blindness; Polymerase Chain Reaction; Polymorphism, Single-Stranded Conformational; Retinaldehyde; Retinitis Pigmentosa

Cellular retinaldehyde-binding protein (CRALBP) is abundantly expressed in the retinal pigment epithelium (RPE) and Muller cells of the retina, where it is thought to function in retinoid metabolism and visual pigment regeneration. Mutations in human CRALBP that destroy retinoid binding have been linked to autosomal recessive retinitis pigmentosa. To identify the DNA elements that regulate expression of the human CRALBP gene in the RPE, transient transfection studies were carried out with three CRALBP-expressing human RPE cell culture systems. The regions from -2089 to -1539 base pairs and from -243 to +80 base pairs demonstrated positive regulatory activity. Similar activity was not observed with cultured human breast, liver, or skin cells. Since sequence analysis of the -243 to +80 region identified the presence of two photoreceptor consensus element-1 (PCE-1) sites, elements that have been implicated in photoreceptor gene regulation, the role of these sequences in RPE expression was examined. Mutation of either PCE-1 site significantly reduced reporter activity, and mutation or deletion of both sites dramatically reduced activity. Electrophoretic mobility shift analysis with RPE nuclear extracts revealed two complexes that required intact PCE-1 sites. These studies also identified two identical sequences (GCAGGA) flanking PCE-1, termed the binding CRALBP element (BCE), that are also important for complex formation. Southwestern analysis with PCE-1/BCEcontaining probes identified species with apparent masses near 90-100 and 31 kDa. These results begin to identify the regulatory regions required for RPE expression of CRALBP and suggest that PCE-1-binding factor(s) may play a role in regulating RPE as well as photoreceptor gene expression.

Topics: Carrier Proteins; Cells, Cultured; Consensus Sequence; DNA-Binding Proteins; Gene Expression Regulation; Genes, Reporter; Humans; Mutagenesis, Site-Directed; Nuclear Proteins; Oligodeoxyribonucleotides; Pigment Epithelium of Eye; Promoter Regions, Genetic; Retinaldehyde; Retinitis Pigmentosa; Transfection

A therapeutic effect of vitamin A supplementation on the course of photoreceptor degeneration, previously reported for patients with retinitis pigmentosa, was tested in two transgenic mouse models of this disease, each carrying a dominant rhodopsin mutation. The threonine-17 --> methionine (T17M) mutation is a class II rhodopsin mutation, characterized by a thermal instability/folding defect and minimal regeneration with the chromophore. The proline-347 --> serine (P347S) mutation belongs to class I, comprised of a smaller number of mutations that exhibit no recognized biochemical abnormality in vitro. In the present study, each of the two mouse models was fed a diet containing 2.5 mg of vitamin A palmitate (control) or 102.5 mg of vitamin A palmitate (high vitamin A) per kilogram of diet. Dark-adapted, full-field electroretinograms showed that the high vitamin A diet significantly reduced the rate of decline of a-wave and b-wave amplitudes in the T17M mice but had no significant effect on the decline of electroretinogram amplitude in the P347S mice. Correspondingly, histologic evaluation revealed that the treatment was associated with significantly longer photoreceptor inner and outer segments and a thicker outer nuclear layer in the T17M mice but had no effect on photoreceptor morphology in the P347S mice. In a separate series of experiments, the instability defect of the T17M mutant opsin expressed in vitro was partially alleviated by inclusion of 11-cis-retinal in the culture media. These results show that vitamin A supplementation slows the rate of photoreceptor degeneration caused by a class II rhodopsin mutation. Vitamin A supplementation may confer therapeutic benefit by stabilizing mutant opsins through increased availability of the chromophore.

Topics: Animals; Cells, Cultured; Diterpenes; Electroretinography; Gene Expression; Humans; Liver; Mice; Mice, Transgenic; Microscopy, Electron; Photoreceptor Cells; Point Mutation; Retina; Retinaldehyde; Retinitis Pigmentosa; Retinyl Esters; Rhodopsin; Transfection; Vitamin A

Inadequate levels of all-trans-retinol in the blood cause retinal dysfunction; hence, genes implicated in retinal vitamin-A metabolism represent candidates for inherited retinal degenerations. In the current study, molecular genetic analysis of a consanguineous pedigree segregating for non-syndromic autosomal recessive retinitis pigmentosa (arRP) indicated that the affected siblings were homozygous by descent for a G4763A nucleotide substitution in RLBP1, the gene encoding cellular retinaldehyde-binding protein (CRALBP). This substitution is predicted to replace an arginine with glutamine at residue 150. CRALBP is not expressed in photoreceptors but is abundant in the retinal pigment epithelium (RPE) and Müller cells of the neuroretina, where it carries 11-cis-retinol and 11-cis-retinaldehyde. When expressed in bacteria, recombinant CRALBP (rCRALBP) containing the R150Q substitution was less soluble than wild-type rCRALBP. Mutant rCRALBP was purified from the soluble cell lysate and the protein structure was verified by mass spectrometry. The mutant protein lacked the ability to bind 11-cis-retinaldehyde. These findings suggest that arRP in the current pedigree results from a lack of functional CRALBP, presumably leading to disruption of retinal vitamin-A metabolism.

Topics: Amino Acid Sequence; Base Sequence; Carrier Proteins; Consanguinity; Conserved Sequence; DNA Mutational Analysis; DNA Primers; Female; Genes, Recessive; Humans; In Vitro Techniques; Male; Molecular Sequence Data; Mutation; Pedigree; Polymerase Chain Reaction; Recombinant Proteins; Retinaldehyde; Retinitis Pigmentosa

Two different mutations of the active-site Lys-296 in rhodopsin, K296E and K296M, have been found to cause autosomal dominant retinitis pigmentosa (ADRP). In vitro studies have shown that both mutations result in constitutive activation of the protein, suggesting that the activated state of the receptor may be responsible for retinal degeneration in patients with these mutations. Previous work has highlighted the potential of retinylamine analogs as active-site directed inactivators of constitutively active mutants of rhodopsin with the idea that these or related compounds might be used therapeutically for cases of ADRP involving mutations of the active-site Lys. Unfortunately, however, amine derivatives of 11-cis-retinal, although highly effective against a K296G mutant of rhodopsin, were without affect on the two naturally occurring ADRP mutants, presumably because of the greater steric bulk of Glu and Met side chains in comparison to Gly. For this reason we synthesized a retinylamine analog one carbon shorter than the parent 11-cis-retinal and show that this compound is indeed an effective inhibitor of both the K296E and K296M mutants. The 11-cis C19 retinylamine analog 1 inhibits constitutive activation of transducin by these mutants and their constitutive phosphorylation by rhodopsin kinase, and it does so in the presence of continuous illumination from room lights.

Topics: Animals; Binding Sites; COS Cells; Diterpenes; Genes, Dominant; Humans; In Vitro Techniques; Phosphorylation; Point Mutation; Recombinant Proteins; Retinaldehyde; Retinitis Pigmentosa; Rhodopsin

Retinitis pigmentosa (RP) is a group of genetically and clinically heterogeneous retinopathies, some of which have been shown to result from mutations in two different known retinal genes, rhodopsin (3q) and peripherin-rds (6p). Three additional anonymous loci at 7p, 7q and pericentric 8 have been implicated by linkage studies. There are still, however, a few families in which all known loci have been excluded. In this report we present data indicating a location, on the short arm of chromosome 17, for the autosomal dominant RP (ADRP) locus in a large South African (SA) family of British ancestry. Positive two-point lod scores have been obtained for nine markers (D17S938, Z = 5.43; D17S796, Z = 4.82; D17S849, Z = 3.6; D17S786, Z = 3.55; TP53, Z = 3.55; D17S578, Z = 3.29; D17S960, Z = 3.16; D17S926, Z = 1.51; D17S804, Z = 0.47 all at theta = 0.10 except D17S804 and D17S926, theta = 0.20). These data provide definitive evidence for the localization of an ADRP gene on chromosome 17p. The human recoverin gene has been localized to 17p13.1 and was consequently a prime candidate for ADRP in the family studied. However, mutation screening of the three exons of this gene failed to produce any evidence of recoverin being the gene involved in the pathogenesis of ADRP in this SA family.

Topics: Calcium-Binding Proteins; Chromosome Mapping; Chromosomes, Human, Pair 17; DNA; Exons; Eye Proteins; Female; Genes, Dominant; Genetic Linkage; Genetic Markers; Hippocalcin; Humans; Intermediate Filament Proteins; Lipoproteins; Lod Score; Male; Membrane Glycoproteins; Nerve Tissue Proteins; Pedigree; Peripherins; Recoverin; Retinaldehyde; Retinitis Pigmentosa; Rhodopsin; South Africa

A lysine to glutamic acid substitution at codon 296 in the rhodopsin gene has been reported in a family with autosomal dominant retinitis pigmentosa. This mutation is of particular functional interest as this lysine molecule is the binding site of 11-cis-retinal. The clinical features of a family with this mutation have not been reported previously. We examined 14 patients with autosomal dominant retinitis pigmentosa and a lysine-296-glutamic acid rhodopsin mutation. Four had detailed psychophysical and electrophysiological testing. Most affected subjects had severe disease with poor night vision from early life, and marked reduction of visual acuity and visual field by their early forties. Psychophysical testing showed no demonstrable rod function and severely reduced cone function in all patients tested.

Topics: Adolescent; Adult; Aged; Binding Sites; Dark Adaptation; Electroretinography; Female; Fundus Oculi; Genes, Dominant; Humans; Lysine; Male; Middle Aged; Mutation; Night Blindness; Pedigree; Retinaldehyde; Retinitis Pigmentosa; Rhodopsin; Vision Disorders; Visual Fields

Recently, mutations of the active site Lys296 residue in rhodopsin (Lys296-->Glu and Lys296-->Met) have been found as the cause of disease in some patients with autosomal dominant retinitis pigmentosa. In vitro, these mutations result in constitutive activation of the protein. In an effort to develop a potential therapeutic agent for treatment of the disease, we have examined various amine derivatives of 11-cis- and 9-cis-retinal for ability to irreversibly inactivate a related constitutively active mutant, K296G. Three amines were prepared by reductive amination of retinal: 11-cis-retinylpropylamine, 11-cis-retinylamine, and 9-cis-retinylamine. All three compounds inactivated K296G, and the inactivation could not be reversed upon exposure to light. None of the compounds inactivated the wild-type protein. Although the amines were not effective on the naturally occurring retinitis pigmentosa mutants, presumably because of unfavorable steric interactions with the bulky Glu and Met side chains at position 296, the success with K296G makes it highly encouraging that this approach will evolve related compounds that are capable of inactivating the naturally occurring mutants as well.

Topics: Amines; Amino Acid Sequence; Animals; Binding Sites; Cattle; Humans; Kinetics; Lysine; Molecular Structure; Point Mutation; Retinaldehyde; Retinitis Pigmentosa; Rhodopsin; Structure-Activity Relationship; Transducin

Autosomal dominant retinitis pigmentosa (ADRP) is a hereditary form of retinitis pigmentosa which accounts for about 15% of all types of the latter disease. Recently, close to 50 mutations, mostly point mutations, have been identified in the rhodopsin gene in ADRP patients. We have introduced these mutations in the synthetic bovine rhodopsin gene and herein report on the expression of the mutant genes in COS-1 cells and studies in vitro of the properties of the expressed opsins. The mutant phenotypes fall into three classes: Class I mutants are expressed in COS-1 cells at wild-type levels, form the normal rhodopsin chromophore with 11-cis-retinal, and are transported to the cell surface. However, on illumination, they activate transducin inefficiently. Class II mutants remain in the endoplasmic reticulum and do not bind 11-cis-retinal to form the chromophore. Class III mutants are expressed at low levels and form rhodopsin chromophore only poorly. They also remain in the endoplasmic reticulum and, as expected, show high mannose glycosylation. Nearly all of the mutants studied show abnormal sensitivity to light compared to the wild type, and they activate transducin less efficiently. We conclude that the majority of the ADRP mutants have folding defects.

Topics: Amino Acid Sequence; Animals; Biological Transport; Cattle; Cell Line; Cell Membrane; Endoplasmic Reticulum; Gene Transfer Techniques; Glycosylation; Mannose; Molecular Sequence Data; Mutagenesis; Photochemistry; Point Mutation; Protein Folding; Protein Structure, Secondary; Retinaldehyde; Retinitis Pigmentosa; Rhodopsin; Structure-Activity Relationship

We used a cDNA fragment corresponding to the human cellular retinaldehyde binding protein (CRALBP) gene to search for mutations at this locus in patients with autosomal dominant, autosomal recessive, or isolate retinitis pigmentosa, and Usher's syndrome, type I. No gene deletions or rearrangements could be detected in any patient by Southern blotting. We identified a Pvu II restriction fragment length polymorphism (RFLP) defining two alleles at the CRALBP locus in the normal population. We used this RFLP to analyze the genomic DNA of large sets of unrelated patients with autosomal dominant, autosomal recessive, or isolate retinitis pigmentosa. Within each of these groups, RFLP alleles at the CRALBP locus showed no linkage disequilibrium (departure from Hardy-Weinberg equilibrium). In addition, two autosomal dominant, two autosomal recessive, and three Usher's syndrome, type I pedigrees each showed no cosegregation of the CRALBP locus and the disease locus. We could find no evidence that mutations of the CRALBP gene are associated with the common forms of retinitis pigmentosa or Usher's syndrome, type I.

Topics: Alleles; Carrier Proteins; DNA; Female; Humans; Male; Mutation; Pedigree; Polymorphism, Restriction Fragment Length; Retinaldehyde; Retinitis Pigmentosa