GNAT2 and achromatopsia: Pathogenic variants in six genes encoding proteins composing the cone phototransduction cascade (CNGA3, CNGB3, PDE6C, PDE6H, GNAT2) and of the unfolded protein response (ATF6) have been related to ACHM cases, while CNGA3 and CNGB3 alone are responsible for most cases.