The CABP4 gene encodes a CaBP4, a photoreceptor-specific protein that belongs to a subfamily of neuronal Ca(+2) -binding proteins (CaBPs) with high similarity to calmodulin (CaM).  CaBP4 is localized in the photoreceptor synaptic terminal in the retina, and is required for normal neurotransmission to bipolar cells.  CaBPs may enhance the Ca+2 signaling potential in neurons and other excitable cells.  Defects in this protein are the cause of cone-rod synaptic disorder, congenital non-progressive (CRSD) and congenital stationary night blindness, type 2B.  CRSD is an autosomal recessive non-progressive retinal disorder, characterized by stable low vision, nystagmus, photophobia, a normal or near-normal fundus appearance, and no night blindness.

The CABP4 gene was mapped to 11q13.2 chromosome; it encodes a protein of 275 amino acids.  It has six coding exons and spans approximately 9 kb in the genomic DNA.  Mutations within this gene have been found in patients with cone-rod synaptic disorder, congenital non-progressive (CRSD) and congenital stationary night blindness, type 2B.