Hindbrain patterning and differentiation of many neurons are normal in dtrte370a mutants. All panels depict dorsal views (except E, F), with rostral to the left, of whole-mounted embryos analyzed either by immunohistochemistry (C-F) or by in situ hybridization (A,B,G-J). Double arrows (C,G) mark the midline. (A) In a 28 HPF wild-type sibling, rtk1 (EphA4) is expressed in r1, r3 and r5. (B) In a dtrte370a homozygote, rtk1 expression is normal. (C) In a 36 HPF wild-type sibling, the 3A10 antibody labels the Mauthner cells (arrowhead) and their axons, which cross the midline and extend caudally into the spinal cord. (D) In a dtrte370a homozygote, the Mauthner cells (arrowhead) and their axons are unaffected. (E) In a 36 HPF wild-type sibling, a transverse section at the level of rhombomere 5 reveals zn5 antibody-labeled commissural neurons (black arrowheads) and their axons (arrow), and the abducens motor neurons medially (white arrowhead). (F) In a dtrte370a homozygote, the commissural neurons (arrowheads) and their axons (arrow) are unaffected, but the abducens motor neurons are missing. The difference in staining intensity between E and F results from the different thicknesses of the sections, which were done by hand. The break in the commissural axons in F is due to a crack in the tissue. (G) In a 20 HPF wild-type sibling, the tag1-expressing presumptive nVII neurons (arrowhead) span r5, r6 and r7. The prominent patches of labeling located laterally, rostral and caudal to the otocyst (oto), represent tag1 expression in cranial sensory ganglia. (H) In a dtrte370a homozygote, the presumptive nVII neurons are missing, but the cranial ganglia are unaffected. (I) In a 24 HPF wild-type sibling, shh is expressed in the floor plate (arrow) throughout the midbrain and hindbrain, and in the ventral neuroectoderm in the forebrain. tag1 expression in the nVII neurons (arrowhead) and in the cranial ganglia is also evident. (J) In a dtrte370a homozygote, the nVII neurons are missing. However, shh is expressed normally in the floor plate (arrow), and the cranial ganglia are unaffected. ac, acoustic ganglion; oto, otocyst; tg, trigeminal ganglion; pl, posterior lateral line ganglion. Scale bar, (A,B,I,J) 100 μm, (C,D) 50 μm, (E,F) 25 μm, (G,H) 40 μm.
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