OPN1MW is a gene that encodes for the medium-wavelength-sensitive (M) opsin protein, also known as the green cone pigment. This protein is a crucial component of the human visual system, responsible for detecting light in the green portion of the visible spectrum. It is expressed in cone photoreceptor cells located in the retina.
The OPN1MW gene is located on the X chromosome. Variations in this gene are a common cause of red-green color blindness, specifically deuteranomaly (reduced sensitivity to green light) and deuteranopia (complete absence of green light sensitivity). These conditions are more prevalent in males due to their possessing only one X chromosome, making them hemizygous for the gene.
The M opsin protein, encoded by OPN1MW, belongs to the G protein-coupled receptor superfamily. Upon absorbing a photon of light, the retinal chromophore within the opsin protein undergoes isomerization. This conformational change initiates a signaling cascade that ultimately leads to a neural signal being sent to the brain, where it is interpreted as color vision.
Duplications and deletions involving the OPN1MW gene, as well as sequence variations (single nucleotide polymorphisms, or SNPs), can significantly affect the protein's function and, consequently, an individual's color perception. The highly polymorphic nature of the OPN1MW gene locus contributes to the spectrum of red-green color vision phenotypes observed in the human population.