HCN2 and infection: As a complementary genetic approach, we infected wild-type neurons using three separate short hairpins against Hcn1 and Hcn2. Both alone and in combination, infection of RGC and DRG neurons with the shHcn1/2 constructs resulted in rapid neuronal death within 6 hours (Supplementary Fig. 4A, B), demonstrating that Hcn1 and Hcn2 presence is required for neuronal survival.