NYX

Variants (also called mutations) in the NYX gene have been identified in people with X-linked congenital stationary night blindness. NYX gene variants are responsible for the complete form of the disorder, which is characterized by difficulty seeing in low light (night blindness), loss of sharpness (reduced visual acuity), severe nearsightedness (high myopia), involuntary movements of the eyes (nystagmus), and eyes that do not look in the same direction (strabismus).

Many NYX gene variants change single protein building blocks (amino acids) in nyctalopin. NYX gene variants can change the size or shape of the protein or prevent it from attaching to the surface of bipolar cells. A loss of functional nyctalopin disrupts the ability of photoreceptor cells to transmit visual signals to bipolar cells, which impairs vision in people with X-linked congenital stationary night blindness. The rod pathway is severely disrupted, while the function of cones is only mildly affected.

Variants in the NYX gene have been found to cause high myopia without the other vision problems that are characteristic of X-linked congenital stationary night blindness. The variants responsible for high myopia each change a single amino acid in nyctalopin, which produces an unstable protein and leads to vision problems.