Developmental Assembly of Transduction Apparatus in Chick Basilar Papilla

Abstract

Hair cells, the sensory receptors of auditory and vestibular systems, use a transducer apparatus that renders them remarkably sensitive to mechanical displacement as minute as 1 nm. To study the embryonic development of the transducer apparatus in hair cells of the chick auditory papilla, we examined hair cells that have been labeled with N-(3-triethylammoniumpropyl)-4-(4-(dibutylamino)styryl) pyridiniumdibromide, which has been shown to permeate the transducer channels. In addition, mechanotransduction currents were recorded directly using whole-cell patch-clamp techniques. The structure of the hair bundle was examined using scanning electron microscopy, and immunofluorescence labeling for myosin 1c, myosin 7a, and plasma membrane Ca2+ ATPase 2 was studied to determine the developmental expression of these proteins in embryonic chick papillas. We demonstrate that the transducer apparatus is assembled jointly at embryonic day 11 (E11) of the developing chick basilar papilla. The resting open probability of the transducer channels was high at E12 (approximately 0.5) and remained substantially elevated at E14-16; it then declined to the mature value of approximately 0.15 at E21. The displacement sensitivity of the transduction apparatus, the gating force, increased from E12 to E21. Although the expression of different components of the transducer apparatus and the transduction current peaked at approximately E14-16, marked refinement occurred beyond E16. For example, myosin 1c appeared diffusely localized in hair bundles from E12 to E16, but subsequently consolidated into punctate pattern. The fine temporal and precise spatial assembly of the transducer apparatus likely contributes toward the exquisite sensitivity of the transduction ensemble.

Stepwise Morphological and Functional Maturation of Mechanotransduction in Rat Outer Hair Cells

“…Data presented are similar to those described in avian auditory hair cells (Si et al, 2003) but for shift in the activation curve. In contrast to data presented here, the activation curve shifted from left to right in avian basilar papilla, indicating a large probability of opening that decreased during maturation.…”

“…The all-or-none hypothesis suggests that the MET complex, including the adaptation components, assembles at the base of the stereocilia and migrates intact to the tops of the stereocilia. In contrast, data from chick basilar papilla (Si et al, 2003) revealed a maturation process in which the size of the MET current increased, adaptation got faster and more complete, and the current-displacement plot shifted rightward, meaning the resting open probability decreased during maturation. This pattern of development indicated that the MET complex assembly undergoes a period of refinement and consolidation.…”

Cells of adult brain germinal zone have properties akin to hair cells and can be used to replace inner ear sensory cells after damage

“…Another similarity between ependymal cells and HCs is that ependymal cells express partially open large-conductance cation channels that are permeable to FM1-43 akin to mechano-sensitive channels in HCs. Ependymal cells show rapid (Ͻ60 s) FM1-43 uptake, which was inhibited by dihydrostreptomycin (26,27) (Fig. 4C1 and 2).…”

“…In addition, immunohistochemical techniques were used to examine the expression of cell-specific proteins. Assay for mechanosensory transduction used in our previous report (27) was adopted for ependymal cell.…”

Origin of Inner Ear Hair Cells: Morphological and Functional Differentiation from Ciliary Cells into Hair Cells in Zebrafish Inner Ear

“…Concurrently, hair cells begin to take up FM1-43 and exhibit mechanotransducer currents between E16 and E17 (Géléoc and Holt, 2003). Chicken and mice cochlear hair cells follow the same sequence (Si et al, 2003;Waguespack et al, 2007;Lelli et al, 2009).…”