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Developmental regulation of ephA4 expression in the chick auditory brainstem

Authors

  • Karina S. Cramer,

    1. Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology, Head and Neck Surgery, University of Washington, Seattle, Washington 98195
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  • Melissa H. Rosenberger,

    1. Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology, Head and Neck Surgery, University of Washington, Seattle, Washington 98195
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  • Deanna M. Frost,

    1. Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology, Head and Neck Surgery, University of Washington, Seattle, Washington 98195
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  • Sarah L. Cochran,

    1. Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology, Head and Neck Surgery, University of Washington, Seattle, Washington 98195
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  • Elena B. Pasquale,

    1. Neurobiology Program, Burnham Institute, La Jolla, California 92037
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  • Edwin W Rubel

    Corresponding author
    1. Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology, Head and Neck Surgery, University of Washington, Seattle, Washington 98195
    • Virginia Merrill Bloedel Hearing Research Center, Box 357923, University of Washington, Seattle, WA 98195
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Abstract

The avian auditory brainstem nuclei nucleus magnocellularis (NM) and nucleus laminaris (NL) display highly precise patterns of neuronal connectivity. NM projects tonotopically to the dorsal dendrites of ipsilateral NL neurons and to the ventral dendrites of contralateral NL neurons. The precision of this binaural segregation is evident at the earliest developmental stage at which connections can be observed. We have begun to examine the possibility that Eph receptor tyrosine kinase signaling is involved in establishing these spatially segregated connections. The expression of the EphA4 tyrosine kinase was examined at several developmental stages. EphA4 is expressed in rhombomere 5, which contains progenitors for both NM and NL. In this rhombomere, the labeling becomes striped during the time that precursor cells migrate to the auditory anlage. At the precise time when NM-NL projections are forming, EphA4 expression in NL is asymmetric, with markedly higher expression in the dorsal NL neuropil than in the ventral neuropil, suggesting a possible role in guiding growing axons to the appropriate region. At later embryonic ages EphA4 expression is symmetric around NL, and is absent in NM. As auditory function matures, EphA4 expression decreases so that by 4 days after hatch no EphA4 antibody labeling is evident in the auditory brainstem nuclei. J. Comp. Neurol. 426:270–278, 2000. © 2000 Wiley-Liss, Inc.

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