The Journal of Neuroscience, January 25, 2006, ():
Compartmentalized and Signal-Selective Gap Junctional Coupling in the Hearing Cochlea
J. Neurosci. Jagger and Forge
26: 1260
Supplemental data
Files in this Data Supplement:
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Supplementary Figure 1. Estimated membrane capacitance (Cm) of cells in the medial (inner hair cell) supporting cell region, and the lateral (outer hair cell) supporting cell region during cochlear development. In the lateral region at P0 Cm was very low, reflecting the low gap junctional coupling compared to the medial region. Cm was not significantly different between all groups from P8 onwards (P > 0.05 for all comparisons, unpaired t tests). Although Cm at hearing onset may have been expected to be lower than at P8 (as dye-transfer was less extensive), this may be offset by increases of individual cell Cm during maturation.
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Supplementary Figure 2. Freeze-fracture replicas of organ of Corti at P0. a – c: Köllicker’s organ. a, Low power view reveals columnar epithelial cells that constitute Köllicker’s organ. Boxes enclose areas shown at higher power in b and c. b, At the lumenal end of a cell, numerous, often quite large gap junction plaques (arrows) are evident just below the level of the tight junction complex (which appears as a series of parallel strands around the neck of the cell; arrowheads). c, At the basal end of the same cell, gap junction plaques are less numerous, and generally smaller than those at the lumenal end of the cell. d – f: Pillar cell region of the organ of Corti. d, Low power view for orientation. Inner pillar cells (IPC) and outer pillar cells (OPC) are in contact and their adjacent plasma membranes are exposed (IHC, inner hair cell; OHC, outer hair cell). Boxes enclose regions shown at higher power in e and f. Neither in the area just below the tight junction (e), nor basally (f) are there gap junction plaques evident on the membrane faces in the regions where the outer pillar cells and inner pillar cells are adjacent. Scale bars: a,d: 2μm;b,c,e,f:0.5μm.
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Supplementary Figure 3. Freeze-fractures demonstrate the maturity of GJIC in the organ of Corti at P12. a, Radial fracture across organ of Corti in the basal region just above the basilar membrane. Nerves running through the habenular perforata (HP) to the base of the inner hair cell (IHC) are exposed. The tunnel of Corti (TC) is open, and an inner pillar cell (IPC) is also revealed. The box encloses the area shown in panel b. b, Membrane face where the inner pillar cell is in contact with another inner pillar cell in the longitudinal direction along the organ of Corti. The membrane face is covered with a single large gap junction plaque, some borders of which are indicated by arrows. c, Fracture through outer hair cell (OHC) region revealing OHC and Deiters’ cells (DC). Box frames area shown at higher power in d. d, Membrane faces in region of contact between adjacent Deiters’ cells. Numerous gap junction plaques (arrows) are exposed. Scale bars: a,c:5 μm; b,d: 0.5μm.
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Supplementary Figure 4. A schematic representation of cochlear gap junctional intercellular communication after the onset of hearing. Supporting cells are organized into medial and lateral compartments, likely buffering K+ from inner hair cells and outer hair cells, respectively. Red cells represent presumed pathways of K+ flux only (based on the spread of neurobiotin). Yellow cells represent both local metabolic signaling via D-myo-inositol-1,4,5-trisphosphate (based on the spread of Lucifer yellow), and K+ flux. Pillar cells (blue) provide a non-conductive division between the compartments.
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Supplementary Figure 5. Supporting cells segregate into separate compartments around the onset of hearing, as demonstrated by changes of neurobiotin transfer. At P8, the supporting cells form a continuous syncitium. After the onset of hearing, supporting cells are segregated into medial and lateral compartments. These are dedicated to the homeostasis of inner hair cells (medial) and outer hair cells (lateral).
