11-cis-retinal and Color-Vision-Defects

Serving as one of our primary environmental inputs, vision is the most sophisticated sensory system in humans. Here, we present recent findings derived from energetics, genetics and physiology that provide a more advanced understanding of color perception in mammals. Energetics of cis-trans isomerization of 11-cis-retinal accounts for color perception in the narrow region of the electromagnetic spectrum and how human eyes can absorb light in the near infrared (IR) range. Structural homology models of visual pigments reveal complex interactions of the protein moieties with the light sensitive chromophore 11-cis-retinal and that certain color blinding mutations impair secondary structural elements of these G protein-coupled receptors (GPCRs). Finally, we identify unsolved critical aspects of color tuning that require future investigation.

Topics: Animals; cis-trans-Isomerases; Color Perception; Color Vision Defects; Humans; Mammals; Receptors, G-Protein-Coupled; Retinal Cone Photoreceptor Cells; Retinal Pigments; Retinaldehyde; Rhodopsin

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; Color Perception; Color Vision Defects; Genotype; Humans; Phenotype; Photoreceptor Cells; Retinal Pigments; Rhodopsin

Topics: Amino Acid Sequence; Color Vision Defects; Female; Humans; Male; Molecular Biology; Mutation; Retinal Pigments; Retinitis Pigmentosa; Rhodopsin

The gene structures of three color pigments have been reported by Nathans et al. in 1985. One copy of red gene and 1 to 3 copies of green genes are tandemly repeated on X chromosome. As the structures of red and green genes are highly homologous (96%) and tandemly repeated, they cross-over on chromosome during meiosis and hybrid genes were produced. The function of these hybrid genes exhibits abnormal spectrum for red and green light. The 5' portion of the gene determines which cone cell type express the gene and the 3' portion of the gene determines the type of spectrum. In the 3' portion, exon 4 are associated with a small shift of spectrum and exon 5 determines a large shift of spectrum. For example, a hybrid gene with 5' region of red and 3' region of green is expressed in the red cones and exhibits green spectrum. Abnormality of color perception depends on the hybrid ratio of red and green genes.

Topics: Base Sequence; Color Perception; Color Vision Defects; Crossing Over, Genetic; Female; Genes; Humans; Male; Molecular Sequence Data; Photoreceptor Cells; Retinal Pigments; Rhodopsin

To define the distribution of the red/green and blue opsins in cones from donor eyes from an affected member of a clinically well-characterized family with an autosomal dominant form of cone dystrophy.. Tissue was fixed and processed for immunohistochemistry. Cryosections were studied by indirect immunofluorescence, using well-characterized antibodies to cone cytoplasm, rhodopsin, and cone opsins. The cone-associated matrix was also labeled with the lectin PNA. The affected donor eyes were compared to a postmortem matched normal eye.. Electroretinogram (ERG) testing three years prior to the affected member's death showed normal rod function, while the cone b-wave amplitude was reduced 40% below the lower limit of normal. Fundus exam showed only isolated drusen within the macula. Either a normal-appearing or only nonspecific macular findings were noted in the other affected family members who were examined. Immunofluorescence studies showed that blue cone opsin was restricted to the outer segments of blue cones in the affected retina. Red/green opsins were distributed along the entire plasma membrane of these cone types, from the tip of the outer segment to the synaptic base. Cone-associated matrix displayed a heterogeneous distribution. These patterns were observed both in the macula and in the periphery of the affected retina. Cone pedicles appeared larger than normal. In contrast, rhodopsin staining appeared normal.. The immunocytochemical data obtained suggest that the clinical manifestation of this dystrophy is associated with an abnormal distribution of cone red/green opsins. Additionally, changes in the cone pedicles could have contributed to the abnormal cone ERG in this patient.

Topics: Aged; Aged, 80 and over; Color Vision Defects; Electroretinography; Female; Genes, Dominant; Humans; Immunohistochemistry; Male; Pedigree; Retinal Cone Photoreceptor Cells; Retinal Degeneration; Rhodopsin; Rod Opsins

Mutations of the gene encoding rhodopsin are responsible for 30% of the cases autosomal dominant retinitis pigmentosa. Rhodopsin molecules are key G-coupled transmembrane proteins initiating the visual transduction cascade in rods. These cells are specialized retinal cells allowing the detection of low intensity lights. Mutations in the rhodopsin gene lead to the progressive destruction of rods, clinically translated by night blindness, a progressive bilateral loss of the peripheral visual field, and predominant alterations of the rod component of the electroretinograms. Inherited colour vision deficiencies are mainly caused by alterations of the genes encoding coloured opsins. These proteins are G-coupled receptors specialized in visual transduction in the cones. These sensorial cells are localized in the center of the neural retina where they allow the detection of refined details and chromatic lights. Rearrangements of the genes encoding the green and the red color pigments are responsible for daltonism.

Topics: Color Vision Defects; Humans; Mutation; Retinitis Pigmentosa; Rhodopsin

Topics: Chromosome Deletion; Color Vision Defects; Humans; Male; Rhodopsin

Topics: Animals; Cloning, Molecular; Color Perception; Color Vision Defects; DNA; Gene Conversion; Humans; Photoreceptor Cells; Retinal Pigments; Rhodopsin

Protanopes and deuteranopes do not accept the classical dichromatic matches when field size extends to 8 degrees visual angle. Their unique matches of spectral yellow to a mixture of red and green are then mediated by the photoreceptors of small-field dichromacy interacting with a photoreceptor with the spectral sensitivity of rhodopsin. Our data suggest that large-field trichromacy is a general feature of protanopia and deuteranopia.

Topics: Color Perception Tests; Color Vision Defects; Humans; Photoreceptor Cells; Rhodopsin; Visual Fields

Topics: Adult; Color Vision Defects; Dark Adaptation; Densitometry; Female; Humans; Light; Photic Stimulation; Photoreceptor Cells; Psychophysics; Retinal Pigments; Rhodopsin; Time Factors

Topics: Afterimage; Color Vision Defects; Dark Adaptation; Electrophysiology; Female; Fixation, Ocular; Humans; Light; Photic Stimulation; Photoreceptor Cells; Psychophysics; Rhodopsin; Time Factors

Topics: Color Vision Defects; Humans; Photoreceptor Cells; Retinal Pigments; Rhodopsin

Topics: Adaptation, Ocular; Color Vision Defects; Dark Adaptation; Humans; Retinal Cone Photoreceptor Cells; Retinal Pigments; Rhodopsin; Vision, Ocular

Topics: Color; Color Perception; Color Vision; Color Vision Defects; Electroretinography; Humans; Rhodopsin