Journal article
Neurogenin 1 Null Mutant Ears Develop Fewer, Morphologically Normal Hair Cells in Smaller Sensory Epithelia Devoid of Innervation
Journal of the Association for Research in Otolaryngology, Vol.1(2), pp.129-143
06/2000
DOI: 10.1007/s101620010017
PMCID: PMC2504536
PMID: 11545141
Abstract
The proneuronal gene
neurogenin
1 (
ngn1
) is essential for development of the inner-ear sensory neurons that are completely absent in
ngn1
null mutants. Neither afferent, efferent, nor autonomic nerve fibers were detected in the ears of
ngn1
null mutants. We suggest that efferent and autonomic fibers are lost secondarily to the absence of afferents. In this article we show that
ngn1
null mutants develop smaller sensory epithelia with morphologically normal hair cells. In particular, the saccule is reduced dramatically and forms only a small recess with few hair cells along a duct connecting the utricle with the cochlea. Hair cells of newborn
ngn1
null mutants show no structural abnormalities, suggesting that embryonic development of hair cells is independent of innervation. However, the less regular pattern of dispersal within sensory epithelia may be caused by some effects of afferents or to the stunted growth of the sensory epithelia. Tracing of facial and stato-acoustic nerves in control and
ngn1
null mutants showed that only the distal, epibranchial, placode-derived sensory neurons of the geniculate ganglion exist in mutants. Tracing further showed that these geniculate ganglion neurons project exclusively to the solitary tract. In addition to the normal complement of facial branchial and visceral motoneurons,
ngn1
null mutants have some trigeminal motoneurons and contralateral inner-ear efferents projecting, at least temporarily, through the facial nerve. These data suggest that some neurons in the brainstem (e.g., inner-ear efferents, trigeminal motoneurons) require afferents to grow along and redirect to ectopic cranial nerve roots in the absence of their corresponding sensory roots.
Details
- Title: Subtitle
- Neurogenin 1 Null Mutant Ears Develop Fewer, Morphologically Normal Hair Cells in Smaller Sensory Epithelia Devoid of Innervation
- Creators
- Qiufu Ma - Dana Farber Cancer Institute, Boston, MA 02115 USADavid J Anderson - California Institute of Technology, Pasadena, CA 91125 USABernd Fritzsch - Department of Biomedical Sciences, Creighton University, Omaha, NE 68178
- Resource Type
- Journal article
- Publication Details
- Journal of the Association for Research in Otolaryngology, Vol.1(2), pp.129-143
- DOI
- 10.1007/s101620010017
- PMID
- 11545141
- PMCID
- PMC2504536
- NLM abbreviation
- J Assoc Res Otolaryngol
- ISSN
- 1525-3961
- eISSN
- 1438-7573
- Publisher
- Springer-Verlag; New York
- Language
- English
- Date published
- 06/2000
- Academic Unit
- Iowa Neuroscience Institute; Biology; Craniofacial Anomalies Research Center
- Record Identifier
- 9984070855402771
Metrics
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