Reducing Fgf and Notch levels mimics the effects of <i>tfap2a</i> overexpression.

<p>(A-L) Cross-sections (medial left, dorsal up) passing just posterior to the utricular macula and showing expression of <i>ngn1</i> at 28 hpf (A-D), or sections passing through the utricular macula and showing <i>neurod</i> at 37 hpf (E-H) or Isl1 at 37 hpf (I-L) in wild-type control (A, E, I), <i>hs</i>:<i>dnfgfr1</i> embryos (B, F, J), LY411575 inhibitor treated wild-type embryos (C, G, K) and LY411575 inhibitor treated <i>hs</i>:<i>dnfgfr1</i> embryos (D, H, L). All specimens were treated with 0.3% DMSO and heat-shocked at 24 hpf. The otic vesicle is outlined in each image. (M, N) Mean and standard deviation of the total number of <i>ngn1</i> positive cells in the otic epithelium at 28 hpf (M) and total <i>neurod</i> positive SAG precursors at 37 hpf (N) for the genotypes and treatments indicated in the color key (counted from serial sections, n = 3–6 ears per time point). Asterisks (*) indicate significant differences from control embryos and filled squares indicate significant differences relative to <i>hs</i>:<i>dnfgfr1</i> embryos treated with LY411575. (O) Mean and standard deviation of the total number of Isl1 positive SAG neurons at different times for the genotypes and treatments indicated in the color key (n = 6–15 embryos each). In (O) differences between control and experimental specimens were significant at each time point. In addition, LY411575 treated <i>hs</i>:<i>dnfgfr1</i> embryos were significantly different from <i>hs</i>:<i>dnfgfr1</i> alone or LY411575 treatment alone.