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FIG. 3. NeuroD expression in cranial ganglia and placodes of (A)
X. laevis (stage NF 30) and (B) E. coqui (stage TS 4). NeuroD is
expressed in the epibranchial placodes (dorsoventral extension
indicated by yellow arrows) and ganglia (yellow asterisks) of the
facial (VII), glossopharyngeal (IX), and three trunks (X1, X2/X3) of
the vagal nerve in both species. Similarly, the profundal (GPr) and
trigeminal ganglia (GV) of both species express NeuroD, but this
can only clearly be seen in whole mounts of E. coqui, because in X.
laevis these ganglia lie hidden medial to the facial ganglion and the
eye (e), which expresses NeuroD in X. laevis but not yet in E. coqui
at the stage shown. Additional NeuroD expression domains are in
the otic vesicle (ov; out of focal plane in A) and in the placodes and
ganglia of the lateral line nerves in X. laevis. The dorsoventral
extension of the anterodorsal (AD), middle (M), and posterior (P)
lateral line placodes and their underlying ganglia was determined
in serial sections and is indicated with red arrows in (A); corresponding
expression domains are lacking in E. coqui (red arrows in
B). There are two additional lateral line placodes in X. laevis not
shown in (A): the anteroventral (closely fused to the facial epibranchial
placode) and the supratemporal (developing at later
stages) lateral line placode. LB, limb bud. Bar in A, 200 mm (for A
and B). |
