TRPM1 is co-localized with mGluR6 at the tips of ON-BPC dendrites where they receive input from photoreceptors and, like mGluR6, has since been found to be a major locus of mutations causing complete congenital stationary night blindness (CSNB1) in humans [15]–[18]. The gene discussed is GRM6; the disease is congenital stationary night blindness.