GNAT2

The GNAT2 gene provides instructions for making one part (the alpha subunit) of a protein called transducin. This protein, which is necessary for normal vision, is present in light receptor cells called cones. As part of the light-sensitive tissue at the back of the eye (the retina), cones provide vision in bright light, including color vision. Other light receptor cells in the retina, called rods, are responsible for vision in low light.

Transducin plays an essential role in transmitting visual signals from cones in the retina to the brain. Three types of cones each contain a special pigment (a photopigment) that is most sensitive to a particular wavelength of light. When any of the three photopigments absorbs light, it activates the transducin protein. Transducin then triggers a series of chemical reactions within a cone cell. These reactions ultimately alter the cell's electrical charge, generating a signal that the brain interprets as vision.

color vision deficiency - caused by mutations in the GNAT2 gene

Fewer than 10 mutations in the GNAT2 gene have been identified in people with color vision deficiency. These mutations typically cause complete achromatopsia, which is a loss of all color vision. Each of the reported GNAT2 mutations leads to an abnormally small, nonfunctional version of the GNAT2 protein. This altered protein either prevents the assembly of transducin or disrupts transducin's interaction with photopigments. As a result, cones are unable to transmit visual signals to the brain. A loss of normal cone function causes a lack of color vision, reduced sharpness, and other vision problems associated with complete achromatopsia.