Fig. 3
VPA treatment exposes cryptic transcriptional repression of ascl1b by basal levels of Notch signalling. (A) Quantitative reverse-transcriptase PCR showing that VPA mildly reduces her4 expression, whereas DAPT strongly reduces her4 expression to between 12% and 23% of control levels (*P=0.017, **P=0.001). (B) Short duration (8 hour) treatment with VPA [condition (viii)] does not upregulate her4 expression at 32 hpf (n=12/12). Downregulation of her4 expression in hdac1s436 mutant hindbrain at 32 hpf (n=5/5). Scale bar: 50 µm. (C) Concomitant blockade of Notch signalling using the γ-secretase inhibitor DAPT prevents the downregulation of ascl1b by VPA. Loss of her4 expression in DAPT-treated embryos [conditions (ix) and (x)] (upper panels) (n=35/35). Persistence of ascl1b expression in embryos treated with VPA and DAPT [condition (x)] (n=23/23).