Facial motor neurons fail to completely exit r4 and r5 to form clusters in r6 and r7. Panels show a single z-plane image of dorsally mounted whole embryos with anterior to the left. Tg(isl1:GFP)rw0 reporter expression, amplified using an anti-GFP antibody and an Alexa 488 secondary antibody, is revealed as green and RNA expression patterns are blue. A,B:hoxb1a expression marks r4. C–F:egr2b expression labels r3 and r5. G–L:hoxb4a expression begins at the r6/r7 boundary and extends posteriorly. Arrows indicate region where facial motor neurons normally migrate. Approximate location of the otic vesicles is outlined with red ovals. Scale bar = 32 μm.
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