Delay of closure by inhibition of apoptosis in utero. Delayed progression of closures I and II at the forebrain and the MHNP of apoptosis-deficient embryos in utero. The degree of delay in the cranial closures I and II in embryos deficient for apaf-1^−/− (shown in B) or casp-3^−/− (shown in D) was represented as a score sheet. (A) apaf-1^−/− embryo exhibiting delayed closures at the MHNP dorsal view (midbrain–hindbrain) of the embryo. Arrows indicate MHNP edges. d, rostral midbrain; e, caudal midbrain; ov, otic vesicle. (B and D) Representation as a score sheet of the degree of cranial closures I and II in embryos deficient for apaf-1^−/− (B) or casp-3^−/− (D). Each column corresponds to an individual embryo with its somite number, and rows indicate the extent of closure. A score of 0 (yellow) indicates unattached or open. A score of 1 (pink) indicates attached or closed (fused). A score of 0/1 (orange) indicates attached but not yet fused. d and e, closure II in the midbrain (MB). FB, forebrain. (C) Frontal views of casp-3^+/− or casp-3^−/− embryos are shown. Edges of neural plates are traced by white dotted lines. a, rostral forebrain; b, caudal forebrain; c, closure II initiation sites (shown by asterisks); d, rostral midbrain; e, caudal midbrain. (D) Initiation and progression of closure II in controls occur earlier (at around somite 10–12; cl2 initiation rows) than in casp-3^−/− embryos (at around somite 13). Midline sealing at r2–4 was completed around somite stage 16–17 in normal embryos but delayed in apaf-1^−/− and casp-3^−/− embryos. Bars, 100 µm.