Fig. 2

Enteric precursors are absent in baz1 mutants and supernumerary neurons in trunk and tail do not express markers of non-sensory neuronal types.

A,B) phox2b expression at 72 hpf in wild-types (A) is restricted to the enteric neuron progenitors, but is absent from baz1 embryos (B). Tyrosine hydroxylase (TH) immunofluorescence reveals differentiated sympathetic neurons at 7 dpf in WT (C-E, I-K), whereas these are much reduced in baz1 mutants (F-H, L-M). White arrows indicate a subset of TH⁺ neurons. Inset in J represents enlargement of boxed area to show autonomic neuron chain more clearly. Occasional baz1 mutants show anti-TH immunofluorescence in neurons (*) associated with the PLLn (O-Q). DIC (C,F,I,L,O) and immunofluorescent TH images (D,G,J,M,P) are merged in panels E,H,K,N,Q respectively. sb, swim bladder; vs, ventral stripe. R) Quantitation (mean ± s.d.) of anti-TH positive sympathetic neurons in WT (N = 16) and baz1 mutants (N = 16). * indicates significant difference (two-tailed t test, p<0.001) Scale bar, 50 μm(C).