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Fig. 3 Temporal and Spatial Characterization of Representative MO-Induced Neural Cell Death during Early Embryogenesis (A) Brightfield and darkfield images of Wnt5 MO1-injected embryos. 14 hpf (A–I), 22 hpf (J–R), and 30 hpf (S–AA). Uninjected embryos (A–C, J–L, and S–U), intermediate cell death phenotype (D–F, M–O, and V–X), and severe cell death phenotype (G–I, P–R, and Y–AA). Lateral views (A, D, G, J, M, P, S, V, and Y), all others dorsal head views. Intermediate cell death is observed at 14 hpf as highly localized opaque cells in the head (large arrow in D), which are arranged near the lateral (arrowhead in E and F) and midline (small arrow in E and F) areas of the developing brain. This pattern progresses through 22 hpf and 30 hpf (M–O and V–X, respectively), including a concentration of opaque cells surrounding the emerging folds of the brain midline (small arrows N–O and W–X) and the eye (arrowheads N–O and W–X). Severe cell death is observed as highly dense areas of opaque cells throughout the developing head. (B) TUNEL assay. Zebrafish embryos were injected with Wnt5 MO1 and analyzed by TUNEL assay at 14 hpf (A–F), 22 hpf (G–O), and 30 hpf (P–X) stages. Uninjected embryos: A–C, G–I, and P–R. At the later time points two classes of phenotypes were observed: an intermediate (J–L and S-U) and a severely affected class of embryos (M–O and V–X). These were characterized by intense fluorescent apoptotic foci in the head and body, with increasing intensity corresponding to increased severity (higher MO dose). Please see Figure S1 for a higher resolution version of this figure.