GNAT2 encodes the guanine nucleotide-binding protein alpha subunit of cone transducin, a G protein that functions as a critical amplifier in cone phototransduction 1. In cone photoreceptors, GNAT2 couples activated rhodopsin to cGMP-phosphodiesterase, translating light stimulus into electrical signals necessary for color vision 2. The GNAT2 gene spans 9967 base pairs with eight exons and shows cone-specific expression patterns distinct from rod transducin 1. Pathogenic variants in GNAT2 cause achromatopsia (ACHM), a rare autosomal recessive cone dysfunction syndrome characterized by loss of color discrimination, nystagmus, photophobia, and reduced visual acuity 3. GNAT2 mutations account for approximately 1.7% of achromatopsia cases 3. The disease presents at birth or early infancy with highly variable phenotypes; notably, cone photoreceptor structure is relatively well-preserved in GNAT2-associated achromatopsia despite functional deficits, potentially providing a therapeutic window for intervention 4. While no FDA-approved treatment exists, multiple gene therapy approaches targeting GNAT2-achromatopsia are in preclinical development and clinical trial phases 5, offering promise for restoration of visual function in affected patients.