Cloning and developmental expression of nonmuscle myosin IIA (Myh9) in the mammalian inner ear.

MYH9 encoding a nonmuscle myosin heavy chain has been linked to nonsyndromic and syndromic forms of autosomal dominant hereditary hearing loss, suggesting a critical biological role of this motor protein in the auditory organ. While Myh9 expression has been described in the adult mouse, critical parameters pertaining to its developmental expression remain to be characterized. The current study describes cloning of the mouse Myh9 cDNA and the temporal onset and spatial distribution of Myh9 expression in the inner ear of the developing fetus, the neonate, and the adult. The cloned Myh9 cDNA contained two single-base-pair differences from the published genomic sequence: T990C (G330G) and T5198A (L1733Q). Immunoblotting of embryonic (E15.5) and adult tissues from several organs, including the cochlea, identified a single 250-kDa anti-Myh9-immunoreactive band, supporting an absence of Myh9 splice variants in the fetus and the adult. In situ expression analysis identified Myh9 distributed within the epithelial layer of the otic vesicle at E10.5. Myh9 expression was found to persist within the epithelia surrounding the cochlear duct at E13.5 and E16.5. The sensory cells of the developing cochlea were positive for Myh9 expression at E16.5. Within the neonate and the adult cochlea, Myh9 expression was observed within the sensory hair cells and the supporting hair cells of the organ of Corti, the spiral ligament, and the spiral limbus, but not in the stria vascularis. Identification of Myh9 in the developing and mature inner ear suggests a role for this protein in the development and maintenance of auditory function.

Mhatre AN ，Li J ，Kim Y ，Coling DE ，Lalwani AK ... -  《JOURNAL OF NEUROSCIENCE RESEARCH》

Expression of Myh9 in the mammalian cochlea: localization within the stereocilia.

Mhatre AN ，Li Y ，Atkin G ，Maghnouj A ，Lalwani AK ... -  《-》

Calbindin and S100 protein expression in the developing inner ear in mice.

Calbindin (CB) and S100 are calcium-binding proteins expressed in the inner ear in vertebrates. Information about their developmental roles is incomplete. This study investigated the expression patterns of CB and S100 in C3H mice using immunohistochemistry, from embryonic day 11 (E11) to postnatal day 10 (P10). CB was expressed in the otocyst and vestibulocochlear ganglion (VCG) from E11. In the cochlea at E17, CB immunoreactivity clearly labeled the VCG, the outer and inner hair cells, and the stria vascularis. CB staining was also present in the vestibular sensory cells, including their nerve fibers. Two days later, to this expression pattern was added the labeling of Kölliker's organ. Early postnatal CB expression encompassed VCG neurons, auditory hair cells, their afferent nerve fibers, and cells of the cochlear lateral wall. The first signs of S100 immunostaining of cochlear and vestibular epithelial cells appeared at E14. At E17 S100 immunoreactivity was found in a restricted expression pattern in the cochlea. Immunostaining was also present in the sacculus and utriculus and their afferent fibers. The Deiters', pillar and inner hair cells, and the VCG were S100-positive from E19. Postnatally, S100 staining also appeared in the inner hair cells and Deiters' cells, in some VCG neurons, and, in addition, in the spiral limbus, the spiral prominence, and the intermediate cells of the stria vascularis. This study demonstrates that the sites of CB and S100 expression in the mouse inner ear during embryonic and early postnatal development do not overlap and signal independent developmental patterns.

Buckiová D ，Syka J 《-》

Expression of the carrier protein apolipoprotein D in the mouse inner ear.

Hildebrand MS ，de Silva MG ，Klockars T ，Solares CA ，Hirose K ，Smith JD ，Patel SC ，Dahl HH ... -  《-》

Expression of the transcription factors GATA3 and Pax2 during development of the mammalian inner ear.

The transcription factors GATA3 and Pax2 are expressed throughout development of the mouse inner ear. We have used antibodies to study their temporal and spatial expression patterns from embryonic days E8-E16.5. The two factors show reciprocal relationships in the regional patterning of the early otocyst and cellular patterning within the sensory epithelia. GATA3 is expressed in the whole otic placode at E8. In the otocyst at E9.5-10.5, the distribution is lateral and complementary to the medial expression pattern of Pax2. Only Pax2 is expressed in the endolymphatic duct, but both factors are expressed in the cochlea. At E11.5-13.5, GATA3 is expressed strongly in the cochlea, but in the dorsal, vestibular region it is downregulated. In all sensory epithelia, downregulation coincides with sensory innervation. Pax2 is expressed in all sensory and some nonsensory epithelia, but within sensory epithelia at E16.5 it is restricted to hair cells. GATA3 is expressed throughout key periods of cell proliferation, fate determination, and differentiation and is not specifically associated with any of these processes. Expression persists most strongly in the main components of the developing auditory system. These include the auditory sensory epithelium, the afferent and efferent nerves, and the mesenchymal and ectodermal cells in regions that form key parts of the middle and outer ear. GATA3 is thus expressed in functionally distinct groups of cells that integrate to form a complete sensory system. The results suggest that both factors may be involved in tissue compartmentalisation, morphogenesis, and cell signalling.

Lawoko-Kerali G ，Rivolta MN ，Holley M 《JOURNAL OF COMPARATIVE NEUROLOGY》