GRM6 encodes metabotropic glutamate receptor 6 (mGluR6), a G-protein coupled receptor essential for visual signal transmission in retinal ON-bipolar cells 1. The receptor localizes to dendritic tips of both rod and cone ON-bipolar cells, where it mediates glutamate signaling from photoreceptors and is required for normal b-wave generation in electroretinograms 2. Mutations in GRM6 cause complete congenital stationary night blindness (cCSNB), characterized by absent or reduced ERG b-waves due to impaired ON-bipolar cell function 34. Various mouse models with GRM6 mutations demonstrate phenotypes ranging from complete loss of mGluR6 protein and b-wave responses to partial reductions depending on the specific mutation 24. GRM6 mutations are also associated with early-onset high myopia, suggesting broader roles in ocular development 5. Gene therapy approaches using adeno-associated virus delivery can restore mGluR6 localization and partially rescue associated signaling proteins, though functional improvements remain limited 13. The development of human GRM6-specific promoters enables targeted therapeutic approaches for treating cCSNB and potentially optogenetic vision restoration 6.