retinaldehyde and Night-Blindness

Recent molecular genetic studies show how changes in the protein component of a visual pigment alters its absorbance; they also explain the abnormal colour vision of one of the great pioneers of visual science.

Topics: Animals; Cercopithecidae; Chemistry; Chromosomes, Human, Pair 7; Color Perception; Color Vision Defects; England; History, 18th Century; History, 19th Century; Humans; Mutation; Night Blindness; Protein Conformation; Retinal Cone Photoreceptor Cells; Retinaldehyde; Rhodopsin; Rod Opsins; Sequence Homology, Nucleic Acid; X Chromosome

Topics: Animals; Apolipoproteins; Female; Genital Diseases, Female; Genital Diseases, Male; Glycoproteins; Growth; Humans; Lipid Metabolism; Lipoproteins; Male; Membrane Proteins; Molecular Biology; Night Blindness; Photoreceptor Cells; Retinal Pigments; Retinaldehyde; Vitamin A; Vitamin A Deficiency; Xerophthalmia

Rhodopsin is the photosensitive protein, which binds to 11-cis-retinal as its chromophore. In the dark, rhodopsin exists as a stable complex between the opsin moiety and 11-cis-retinal. The absorption of a light photon converts 11-cis-retinal to all-trans-retinal and initiates our vision. As a result, the increase in the rate of dark activation of rhodopsin reduces its photosensitivity resulting in night blindness. The mutations, G90D and T94I are night blindness-causing mutations that exhibit completely different physicochemical characteristics associated with the dark activation of rhodopsin, such as a high rate of thermal isomerization of 11-cis-retinal and a slow pigment regeneration. To elucidate the molecular mechanism by which G90D and T94I mutations affect rhodopsin dark activation and regeneration, we performed light-induced difference FTIR spectroscopy on dark and primary photo-intermediate states of G90D and T94I mutants. The FTIR spectra clearly show that both charged G90D and hydrophobic T94I mutants alter the H-bond network at the Schiff base region of the chromophore, which weakens the electrostatic interaction with Glu113 counterion. Our results further show an altered water-mediated H-bond network around the central transmembrane region of mutant rhodopsin, which is reminiscent of the active Meta-II state. This altered water-mediated H-bond network may cause thermal isomerization of the chromophore and facilitate rhodopsin dark activation.

Topics: Animals; Cattle; Hydrogen Bonding; Isomerism; Models, Molecular; Night Blindness; Point Mutation; Protein Conformation; Retinaldehyde; 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

The G90D rhodopsin mutation is known to produce congenital night blindness in humans. This mutation produces a similar condition in mice, because rods of animals heterozygous (D+) or homozygous (D+/+) for this mutation have decreased dark current and sensitivity, reduced Ca(2+), and accelerated values of tau(REC) and tau(D), similar to light-adapted wild-type (WT) rods. Our experiments indicate that G90D pigment activates the cascade, producing an equivalent background light of approximately 130 Rh* rod(-1) for D+ and 890 Rh* rod(-1) for D+/+. The active species of the G90D pigment could be unregenerated G90D opsin or G90D rhodopsin, either spontaneously activated (as Rh*) or in some other form. Addition of 11-cis-retinal in lipid vesicles, which produces regeneration of both WT and G90D opsin in intact rods and ROS membranes, had no effect on the waveform or sensitivity of dark-adapted G90D responses, indicating that the active species is not G90D opsin. The noise spectra of dark-adapted G90D and WT rods are similar, and the G90D noise variance is much less than of a WT rod exposed to background light of about the same intensity as the G90D equivalent light, indicating that Rh* is not the active species. We hypothesize that G90D rhodopsin undergoes spontaneous changes in molecular conformation which activate the transduction cascade with low gain. Our experiments provide the first indication that a mutant form of the rhodopsin molecule bound to its 11-cis-chromophore can stimulate the visual cascade spontaneously at a rate large enough to produce visual dysfunction.

Topics: Animals; Aspartic Acid; Calcium; Carrier Proteins; cis-trans-Isomerases; Dark Adaptation; Disease Models, Animal; Dose-Response Relationship, Radiation; Eye Proteins; Glycine; Kinetics; Light Signal Transduction; Membrane Potentials; Mice; Mice, Transgenic; Mutation; Night Blindness; Opsins; Photic Stimulation; Retinal Rod Photoreceptor Cells; Retinaldehyde; Rhodopsin; Spectrum Analysis; Time Factors

We report that visual arrestin can regulate retinal release and late photoproduct formation in rhodopsin. Our experiments, which employ a fluorescently labeled arrestin and rhodopsin solubilized in detergent/phospholipid micelles, indicate that arrestin can trap a population of retinal in the binding pocket with an absorbance characteristic of Meta II with the retinal Schiff-base intact. Furthermore, arrestin can convert Metarhodopsin III (formed either by thermal decay or blue-light irradiation) to a Meta II-like absorbing species. Together, our results suggest arrestin may be able to play a more complex role in the rod cell besides simply quenching transducin activity. This possibility may help explain why arrestin deficiency leads to problems like stationary night blindness (Oguchi disease) and retinal degeneration.

Topics: Animals; Arrestin; Dark Adaptation; Micelles; Night Blindness; Protein Binding; Recombinant Proteins; Retinal Rod Photoreceptor Cells; Retinaldehyde; Rhodopsin; Schiff Bases; Spectrophotometry, Ultraviolet; Transducin; Vision, Ocular

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

In an examination of the effect of three rhodopsin night blindness mutations on the rate of association of 11-cis-retinal with opsin, one of the mutations (G90D) was found to slow the rate of reaction by more than 80-fold. This effect does not appear to be general to night blindness mutations as the two other mutants (A292E and T94I) were not found to bind retinal with slowed kinetics. However, T94D was similar to G90D in that the rate of retinal binding was dramatically slowed. Gly90 and Thr94 are both located in the active site of the protein close to the Schiff base counterion Glu113. Thus, the slow kinetics of Schiff base formation appear to correlate with the introduction of a negative charge close to the Schiff base counterion, suggesting a possible role for Glu113 as a catalytic base in this reaction. Consistent with this model, the E113Q mutant was also found to bind retinal more slowly than the wild type.

Topics: Alanine; Amino Acid Sequence; Animals; Aspartic Acid; Glutamic Acid; Glutamine; Glycine; Humans; Molecular Sequence Data; Mutagenesis, Insertional; Night Blindness; Protein Binding; Protein Denaturation; Retinaldehyde; Rhodopsin; Schiff Bases; Spectrophotometry, Ultraviolet; Threonine

Three different mutations of rhodopsin are known to cause autosomal dominant congenital night blindness in humans. Although the mutations have been studied for 10 years, the molecular mechanism of the disease is still a subject of controversy. We show here, using a transgenic Xenopus laevis model, that the photoreceptor cell desensitization that is a hallmark of the disease results from persistent signaling by constitutively active mutant opsins.

Topics: Animals; Animals, Genetically Modified; Disease Models, Animal; Dose-Response Relationship, Drug; Dose-Response Relationship, Radiation; Electrophysiology; Green Fluorescent Proteins; Humans; Luminescent Proteins; Membrane Potentials; Microscopy, Fluorescence; Mutation; Night Blindness; Phenotype; Photic Stimulation; Photoreceptor Cells; Protein Conformation; Retinaldehyde; Rhodopsin; Xenopus laevis

The natural ligand of the retinal photoreceptor rhodopsin, 11-cis-retinal, is isomerized to its all-trans configuration as a consequence of light absorption in the first step of the visual phototransduction process. Here we show, by means of difference spectroscopy and high-performance liquid chromatography analysis, that thermal denaturation of rhodopsin induces the same type of isomerization. This effect is likely due to thermally induced conformational rearrangements of amino acid residues in the retinal-binding pocket--possibly implying helical movements--and highlights the tight coupling between 11-cis-retinal and opsin. This effect could have implications in the instability and functional changes seen for certain mutations in rhodopsin associated with retinal disease, and in the stability of the different conformers induced by mutations in other G protein-coupled receptors.

Topics: Animals; Cattle; Chromatography, High Pressure Liquid; Hot Temperature; Night Blindness; Protein Denaturation; Receptors, G-Protein-Coupled; Retinal Diseases; Retinaldehyde; Rhodopsin; Spectrum Analysis; Stereoisomerism

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

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

Drugs which affect the processing of vitamin A in the retina or pigment epithelium can cause ocular toxicity. It is shown here that the retinoic acids, which are used in the treatment of skin disorders and which cause night blindness, inhibit the ocular retinol dehydrogenases in an in vitro system. This is shown to lead to a decrease in the formation of the visual chromophore 11-cis-retinal, thus explaining why night blindness might occur.

Topics: Alcohol Oxidoreductases; Animals; Diterpenes; Night Blindness; Pigment Epithelium of Eye; Rana pipiens; Retina; Retinaldehyde; Retinyl Esters; Tretinoin; Vitamin A