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Published August 15, 2000 | public
Journal Article

Embryonic Origins of Auditory Brain-Stem Nuclei in the Chick Hindbrain

Abstract

The auditory nuclei of the chick brain stem have distinct morphologies and highly specific synaptic connectivity. Nucleus magnocellularis (NM) and nucleus angularis receive tonotopically ordered cochlear input. NM in turn projects tonotopically to nucleus laminaris (NL), maintaining binaural specificity with projections to either dorsal or ventral NL dendrites. NM and NL arise from a common anlage, which differentiates as the cells migrate and acquire their mature morphologies. NM and NL cells are closely associated during embryogenesis and synapse formation. However, the morphologies of the nuclei and of the cells within the nuclei differ greatly between NM and NL. While later maturation of these nuclei has been described in considerable detail, relatively little is known about the early embryonic events that lead to the formation of these nuclei. We examined the embryonic origins of cells in brain-stem auditory nuclei with particular emphasis on NM and NL. Lipophilic dyes were injected into small regions of the embryonic hindbrain prior to the birth and migration of cells that contribute to these nuclei. We found that NM arises from rhombomeres r5, r6, and r7, and NL arises mostly from r5 with a few cells arising from r6. NM and NL thus have partially overlapping rhombomeres of origin. However, we found that the precursors for NM and NL are found in distinct regions within rhombomere 5, with NM precursors in medial regions and NL precursors in lateral regions. Our results do not support a lineage relationship between NM and NL cells and they suggest that NM and NL are specified prior to migration of precursors to the auditory anlage.

Additional Information

© 2000 Academic Press. Received for publication January 3, 2000. Revised May 11, 2000. Accepted May 11, 2000. Preliminary studies while E.WR. was on sabbatical at Caltech were supported in part by a Wiersma Fellowship. We are grateful to Drs. M. Bronner-Fraser, P. Kulesa, and M. Konishi for valuable suggestions during this study. We are also grateful to G. MacDonald for technical assistance and to D. Molea, Dr. L. Westrum, and Dr. O. Bermingham-McDonogh for helpful suggestions with this study. In addition, we thank Drs. S. Cochran and L. Cunningham for helpful comments on the manuscript. This research was supported by NIH 00395.

Additional details

Created:
August 21, 2023
Modified:
October 17, 2023