Nyctalopin is a protein that in humans is encoded by the NYX gene. It is a leucine-rich proteoglycan which is expressed in the eye, spleen and brain in mice. Mutations in this gene cause congenital stationary night blindness in humans. A mouse strain called nob (no b-wave) carries a spontaneous mutation leading to a frameshift in this gene. These mice are used as an animal model for congenital stationary night blindness.