Dose and timing-response for 1-azakenpaullone on retinal development. The GSK3β inhibitor 1-azakenpaullone was applied to embryos at various stages of development and observations were made at 72 hpf. While control embryos treated with 0.1% DMSO as early as dome stage developed normally (A), treatment with 2.5 μM 1-azakenpaullone (Az) at dome or shield stage resulted in loss of forebrain and eyes (B, C). Treatment with 2.5 μM 1-azakenpaullone at 90% epiboly resulted in a small eye lacking a lens (D). At bud-stage or later, treatment with 1-azakenpaullone led to a small eye, with the size of the eye increasing with progressively later treatments (E-J). The effects of 1-azakenpaullone are dose-dependent: embryos treated at shield stage with 0.5 μM 1-azakenpaullone have relatively normal development (K), 1 μM results in a small eye (L), and treatments at 2.5 μM or higher results in failure of eye development (M-O). Scale bar = 200 μm.