OPN1LW — Opsin 1, Long-Wave-Sensitive

The OPN1LW gene provides instructions for making a protein that is essential for normal color vision. This protein is found in the retina, which is the light-sensitive tissue at the back of the eye. The retina contains two types of light receptor cells, called rods and cones, that transmit visual signals from the eye to the brain. Rods provide vision in low light. Cones provide vision in bright light, including color vision. There are three types of cones, each containing a specific pigment (a photopigment called an opsin) that is most sensitive to particular wavelengths of light. The OPN1LW gene provides instructions for making an opsin pigment that is more sensitive to light in the yellow/orange part of the visible spectrum (long-wavelength light). Cones with this pigment are called long-wavelength-sensitive or L cones. In response to light, the photopigment triggers a series of chemical reactions within an L cone. These reactions ultimately alter the cell's electrical charge, generating a signal that is transmitted to the brain. The brain combines input from all three types of cones to produce normal color vision.

Gene description: The OPN1LW gene provides instructions for making a protein that is essential for normal color vision. This protein is found in the retina, which is the light-sensitive tissue at the back of the eye.

Patient and family guide: The OPN1LW gene provides instructions for making a protein that is essential for normal color vision. This protein is found in the retina, which is the light-sensitive tissue at the back of the eye. The retina contains two types of light receptor cells, called rods and cones, that transmit visual signals from the eye to the brain. Rods provide vision in low light. Cones provide vision in bright light, including color vision. There are three types of cones, each containing a specific pigment (a photopigment called an opsin) that is most sensitive to particular wavelengths of light. The OPN1LW gene provides instructions for making an opsin pigment that is more sensitive to light in the yellow/orange part of the visible spectrum (long-wavelength light). Cones with this pigment are called long-wavelength-sensitive or L cones. In response to light, the photopigment triggers a series of chemical reactions within an L cone. These reactions ultimately alter the cell's electrical charge, generating a signal that is transmitted to the brain. The brain combines input from all three types of cones to produce normal color vision.

Gene function: The OPN1LW gene provides instructions for making an opsin pigment that is more sensitive to light in the yellow/orange part of the visible spectrum (long-wavelength light). Cones with this pigment are called long-wavelength-sensitive or L cones. In response to light, the photopigment triggers a series of chemical reactions within an L cone.

Protein structure: The OPN1LW protein is a multi-pass membrane protein that functions as a G-protein coupled receptor. It consists of an apoprotein, opsin, covalently linked to a light-absorbing chromophore.

Molecular function: Visual pigments are the light-absorbing molecules that mediate vision. They consist of an apoprotein, opsin, covalently linked to cis-retinal. The OPN1LW protein specifically absorbs long-wavelength light (yellow/orange/red) and triggers a signal transduction cascade via G-proteins.

Mutation spectrum: Most red-green color vision defects result from structural rearrangements involving the OPN1LW and OPN1MW genes, such as recombination that deletes genetic material or forms hybrid pigment genes. Less commonly, changes in single DNA building blocks (base pairs) occur. A common polymorphism (Ser180Ala) accounts for subtle differences in normal color vision.

Clinical significance: Several kinds of genetic changes involving the OPN1LW gene cause red-green color vision defects, a form of color vision deficiency that makes it difficult or impossible to distinguish between shades of red, yellow, and green. A rarer form of color vision deficiency, blue cone monochromacy, severely reduces sharpness of vision and affects the ability to perceive most colors.

Inheritance: X-Linked

Chromosomal location: Xq28

Research and therapeutic approaches: Gene therapy approaches are under active investigation for inherited retinal diseases. For example, ADVM-062 is a gene therapy candidate specifically designed to deliver a functional copy of the OPN1LW gene to the foveal cones of patients with Blue Cone Monochromacy.