Fig. 3. Large neuronal cluster formation in the absence of Hh signaling does not require Ngn1 function. Wild-type embryos were injected with ngn1 morpholino (ngn1 MO) at the 1-cell stage. Injected embryos were treated with 6 µg/ml cyclopamine beginning at dome stage. Embryos were fixed at 72 hpf and processed for anti-Hu immunoreactivity. Images are confocal stacks of lateral views of whole-mount embryos. (A) Control embryo showing normal DRG (arrow) and Rohon-Beard (RB) neurons (arrowhead). (B) ngn1 MO-injected embryo showing absence of DRG and RB neurons. The remaining Hu+ cells are spinal cord neurons. (C) ngn1 MO-injected embryo that was also treated with cyclopamine (cyc) showing large neuronal cluster (arrow).