Fig. 7. MH precursors are maintained in ace and noi mutants. (A-D) Double in situ hybridisation for egfp (red) and her5 (blue) in her5PAC:egfp transgenic wild-type, ace and noi siblings at the stages indicated demonstrates that egfp transcription also reproduces her5 expression in ace and noi, and is downregulated following a correct schedule during the MH maintenance phase. (E-G) Live observation of her5PAC:egfp transgenic wild-type, ace and noi siblings under fluorescence microscopy at 24 hpf reveals that most descendants of early her5-positive cells (positive for GFP protein, green) are maintained, although MHB identities, such as cranial motoneurons III and IV (revealed using the isl1:gfp transgene, insets) (Higashijima et al., 2000) are missing. (H-M) Analyses of apoptosis (H-J, Acridine Orange staining) and cell division (K-M, anti-phosphohistone H₃ immunocytochemistry, brown staining) demonstrate that the pattern of cell death and proliferation are comparable in the MH area (bar) in wild-type, ace and noi siblings at least until the 15-somite stage. Embryos in K-M are double stained for wnt1 expression, which is strongly downregulated in ace and absent in noi at that stage (blue staining, arrowheads).

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