Contralateral efferent neurons can be detected in the hindbrain outside of rhombomere 4.
A group of efferent neurons whose bodies are located contralaterally and extend projections across the ventral midline of the hindbrain is considered as a rhombomere 4-specific characteristic. These neurons contribute to the vestibulo-acoustic nerve. At the level of rhombomere 2, a similar kind of efferents have only been described as a result of several experimental manipulations and have been interpreted as being due to rhombomere 2 acquiring rhombomere 4 identity. Here is shown that contralateral efferents can also be detected in rhombomere 2 of normal mouse and chicken hindbrains. These findings indicate that neural processes crossing the midline should not be considered as a rhombomere 4-specific characteristic. They also imply that the formation of the contralateral efferents at different rostro-caudal levels might be under different genetic controls, because Hoxb-1, which is not expressed in rhombomere 2, seems to be essential for their proper formation in rhombomere 4.
Mallo
M
M
Max-Planck-Institut für Immunbiologie, Freiburg, Germany. mallo@immunbio.mpg.de
D000818:Animals; D002232:Carbocyanines; D002642:Chick Embryo; D003391:Cranial Nerves / Q000166:cytology / Q000196:embryology; D005456:Fluorescent Dyes; D051379:Mice; D009476:Neurons, Efferent / Q000166:cytology*; D012249:Rhombencephalon / Q000166:cytology / Q000196:embryology*; D000159:Vestibulocochlear Nerve / Q000166:cytology / Q000196:embryology
D002232:Carbocyanines; D005456:Fluorescent Dyes; C098044:3,3'-dioctadecyloxacarbocyanine