By in vitro follow-up studies of CNGB3-related canine achromatopsia it was found that Asp/Asn mutations affect the heteromeric subunit assembly of the six transmembrane-spanning helices (S1–S6), resulting in the loss of these inter-helical interactions altering the electrostatic equilibrium within in the S1–S4 bundle [21]. The gene discussed is CNGB3; the disease is achromatopsia.