CNGA3 and achromatopsia: –9 Specifically, ATF6 encodes for a transcription factor that has a key role in regulating cell homeostasis, and mutations can contribute to foveal hypoplasia,2 whereas CNGA3 and CNGB3 encode for the α and β subunits, respectively, of the cGMP gated cation channel and account for 80% of ACHM cases.1