Islet-1 expression in the developing chicken inner ear.
The cell types of the inner ear originate from the otic placode, a thickened layer of ectoderm adjacent to the developing hindbrain. The placode invaginates and forms the otic pit, which pinches off as a small vesicle called the otocyst. Presumptive cochleovestibular neurons delaminate from the anterior ventral part of the otocyst and form the cochleovestibular ganglion of the inner ear. Here we show that the LIM/homeodomain protein islet-1 is expressed in cells of the ventral part of the otic placode and that this ventral expression is maintained at the otic pit and the otocyst stages. Auditory and vestibular neurons originate from this islet-1-positive zone of the otocyst, and these neurons maintain islet-1 expression until adulthood. We also demonstrate that islet-1 becomes up-regulated in the presumptive sensory epithelia of the inner ear in regions that are defined by the expression domains of BMP4. The up-regulation of islet-1 in developing inner ear hair and supporting cells is accompanied by down-regulation of Pax-2 in these cell types. Islet-1 expression in hair and supporting cells persists until early postnatal stages, when the transcriptional regulator is down-regulated in hair cells. Our data is consistent with a role for islet-1 in differentiating inner ear neurons and sensory epithelia cells, perhaps in the specification of cellular subtypes in conjunction with other LIM/homeodomain proteins.
Department of Otolaryngology and Program in Neuroscience, Harvard Medical School, and Eaton Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts 02114, USA.
Huawei
H
Li
Hong
H
Liu
Cyrille
C
Sage
Mingqian
M
Huang
Zheng-Yi
ZY
Chen
Stefan
S
Heller
D000199:Actins / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D019521:Body Patterning / Q000502:physiology*; D002642:Chick Embryo; D002645:Chickens; D004268:DNA-Binding Proteins / Q000378:metabolism; D004398:Dyneins; D007758:Ear, Inner / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D004848:Epithelium / Q000196:embryology / Q000254:growth & development / Q000378:metabolism; D017950:Ganglia, Sensory / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006198:Hair Cells, Auditory / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry / Q000379:methods; D017403:In Situ Hybridization / Q000379:methods; D060850:LIM-Homeodomain Proteins; D000081412:Myosin VIIa; D009218:Myosins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D016900:Neurofilament Proteins / Q000378:metabolism; D009474:Neurons / Q000145:classification / Q000378:metabolism*; D051762:PAX2 Transcription Factor; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D012249:Rhombencephalon / Q000196:embryology / Q000254:growth & development / Q000378:metabolism; D013997:Time Factors; D050818:Transcription Factor Brn-3; D014157:Transcription Factors / Q000378:metabolism; D014404:Tubulin / Q000378:metabolism
D000199:Actins; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; C000631456:Myo7a protein, mouse; D000081412:Myosin VIIa; D009419:Nerve Tissue Proteins; D016900:Neurofilament Proteins; D051762:PAX2 Transcription Factor; D050818:Transcription Factor Brn-3; D014157:Transcription Factors; D014404:Tubulin; C462941:beta3 tubulin, mouse; C063843:insulin gene enhancer binding protein Isl-1; D009218:Myosins; D004398:Dyneins; D010751:Phosphopyruvate Hydratase