Journal article
Atoh1 Null Mice Show Directed Afferent Fiber Growth to Undifferentiated Ear Sensory Epithelia Followed by Incomplete Fiber Retention
Developmental dynamics, Vol.233(2), pp.570-583
06/2005
DOI: 10.1002/dvdy.20370
PMCID: PMC1242170
PMID: 15844198
Abstract
Inner ear hair cells have been suggested as attractors for growing afferent fibers, possibly through the release of the neurotrophin brain-derived neurotrophic factor (BDNF).
Atoh1
null mice never fully differentiate hair cells and supporting cells and, therefore, may show aberrations in the growth and/or retention of their innervation. We investigated the distribution of cells positive for
Atoh1
- or
Bdnf
-mediated β-galactosidase expression in
Atoh1
null and
Atoh1
heterozygotic mice and correlated the distribution of these cells with their innervation. Embryonic day (E) 18.5 Atoh1 null and heterozygotic littermates show
Atoh1
- and
BDNF
-β-galactosidase–positive cells in comparable distributions in the canal cristae and the cochlea apex.
Atoh1
-β-galactosidase–positive but only occasional
Bdnf-
β-galactosidase–positive cells are found in the utricle, saccule, and cochlea base of
Atoh1
null mutant mice. Absence of
Bdnf
-β-galactosidase expression in the utricle and saccule of
Atoh1
null mice is first noted at E12.5, a time when
Atoh1
-β-galactosidase expression is also first detected in these epithelia. These data suggest that expression of
Bdnf
is dependent on ATOH1 protein in some but does not require ATOH1 protein in other inner ear cells. Overall, the undifferentiated
Atoh1
- and
Bdnf
-β-galactosidase–positive cells show a distribution reminiscent of that in the six sensory epithelia in control mice, suggesting that ear patterning processes can form discrete patches of
Atoh1
and
Bdnf
expression in the absence of ATOH1 protein. The almost normal growth of afferent and efferent fibers in younger embryos suggests that neither fully differentiated hair cells nor BDNF are necessary for the initial targeted growth of fibers. E18.5
Atoh1
null mice have many afferent fibers to the apex of the cochlea, the anterior and the posterior crista, all areas with numerous
Bdnf
-β-galactosidase–positive cells. Few fibers remain to the saccule, utricle, and the base of the cochlea, all areas with few or no
Bdnf
-β-galactosidase–positive cells. Thus, retention of fibers is possible with BDNF, even in the absence of differentiated hair cells.
Details
- Title: Subtitle
- Atoh1 Null Mice Show Directed Afferent Fiber Growth to Undifferentiated Ear Sensory Epithelia Followed by Incomplete Fiber Retention
- Creators
- B Fritzsch - Creighton University, Department of Biomedical Sciences, Omaha, NebraskaV.A Matei - Creighton University, Department of Biomedical Sciences, Omaha, NebraskaD.H Nichols - Creighton University, Department of Biomedical Sciences, Omaha, NebraskaN Bermingham - Department of Molecular and Human Genetics, Baylor College, Houston, TexasK Jones - Department of Molecular, Cellular and Developmental Biology, Boulder, ColoradoK.W Beisel - Creighton University, Department of Biomedical Sciences, Omaha, NebraskaV.Y Wang - Department of Molecular and Human Genetics, Baylor College, Houston, Texas
- Resource Type
- Journal article
- Publication Details
- Developmental dynamics, Vol.233(2), pp.570-583
- DOI
- 10.1002/dvdy.20370
- PMID
- 15844198
- PMCID
- PMC1242170
- NLM abbreviation
- Dev Dyn
- ISSN
- 1058-8388
- eISSN
- 1097-0177
- Language
- English
- Date published
- 06/2005
- Academic Unit
- Iowa Neuroscience Institute; Biology; Craniofacial Anomalies Research Center
- Record Identifier
- 9984070898902771
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