Plays a role in the synapse formation and synaptic transmission between cone photoreceptor cells and retinal bipolar cells (PubMed:25997951, PubMed:26427409, PubMed:28334377). Required for normal transmission of a light-evoked stimulus from the cone photoreceptor cells to the ON-bipolar cells and ON-ganglion cells in the inner retina (PubMed:26427409, PubMed:28334377). Required in retinal ON-bipolar cells for normal localization of the cation channel TRPM1 at dendrite tips (PubMed:25997951). Seems to play a specific role in synaptic contacts made by ON-bipolar cells with cone photoreceptor pedicles (PubMed:28334377). May also have a role in cone synapse formation (PubMed:25997951, PubMed:28334377). Might facilitate FGFR1 exit from the endoplasmic reticulum to the Golgi (By similarity). Could be a regulator of the FGFRs (By similarity). Punctate expression at dendrite tips. Detected in the outer plexiform layer (OPL) of the retina, where it localizes to rod and cone ON-bipolar cells (at protein level). Also detected in bipolar cell bodies in the inner retinal layer (INL) (at protein level). Viable. Retinal anatomy is grossly normal, although thickness of the INL is reduced. In addition thickness of the innermost region consisting of the inner plexiform layer, ganglion cell layer and optic nerve fiber layer (IPL, GCL, NFL), is reduced. Optomotor responses in dim conditions are impaired. Electroretinography shows completely absent b-wave response under dim conditions, and milder abnormalities under bright conditions (PubMed:24598786). Abolishes ON-responses and delays OFF-responses in retinal ganglion cells (PubMed:28334377). Rod photoreceptors show normal morphology (PubMed:28334377). Cone photoreceptor synapses show morphological abnormalities including a decrease in the number of triad processes in cone pedicles in favor of diad processes, the number of flat contacts at the base of pedicle synapses are increased, deep invaginating contacts made by cone ON-bipolar cells are lost, and vacuole-like structures are present at cone synaptic terminals (PubMed:28334377).