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Fig. 1.
Spectrins αII and βII in the frog and mouse inner ear hair cells. (A–D) Frog (X. laevis). (A) Diagram of the amphibian inner ear, showing the sensory regions of the hearing organ (light green) and of the five balance end organs (dark green). (B and C) Side (B) and top (C) views of the utricular macula. (D) Isolated vestibular hair cells (VHCs). In frog hair cells, spectrins αII and βII are both detected in the cell apical region, specifically, in the cuticular plate (CP) and in the submembrane region of the apical junctional complex. In B and D, F-actin is stained in red by TRITC–phalloidin. (E–G) Mouse. (E) Diagram of the mammalian inner ear, showing the sensory epithelia of the hearing organ (cochlea) and of the five balance end organs. (F) Side views of the anterior crista. The VHCs can be identified by their myosin VIIa immunostaining. As in frog hair cells, spectrins αII and βII are detected mainly in the apical region of VHCs. (G) In isolated VHC and cochlear outer hair cell (OHC), spectrin αII (green) and spectrin βII (red) are both detected in the CP. In the OHC, spectrin αII is also present throughout the lateral wall. By contrast, the αII immunostaining of the VHC lateral wall does not cover the entire cell circumference (see diagrams). Bars, 5 µm. |
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Figure S3: Distribution of α and β spectrin subunits in the frog and mouse inner ears
(A) Frog (X. laevis). Left panels: Cryosections of the saccular macula and of the vestibular
ganglion (containing the cell bodies of the primary sensory neurons) immunostained for spectrins αI
plus βI and for spectrin βIII, respectively (green). Spectrins αI and βI are not detected in the hair
cells (asterisks). The ganglion neurons contain spectrin βIII. Right panels: Whole-mount of the
utricular macula. Among conventional spectrins, only spectrins αII (green) and βII (red) are present
in the sensory hair cells: both spectrins are mainly detected in the cell apical region.
(B) Mouse. Upper panels: Cryosections of the utricular macula and vestibular ganglion
immunostained for spectrins βIII (green, left panel) and βIV (green, right panel). Spectrins βIII and
spectrin βIV are detected in the soma of vestibular ganglion neurons, and at the nodes of Ranvier of
the vestibular axons (arrowheads), respectively, whereas no significant immunostaining is detected
in the sensory epithelium (asterisk). Lower panels: Isolated hair cells (left panels) and wholemounts
(middle panels) of an utricular macula, and whole-mounts of a cochlear sensory epithelium
(right panels) on P10, illustrating the distribution of spectrins αII and βII in the apical region of the
vestibular and cochlear hair cells, mainly in the cuticular plate (CP). In vestibular hair cells (VHC),
a submembrane immunostaining for spectrin αII is occasionally observed (arrowheads). Actin
filaments are stained in red with TRITC-phalloidin, and cell nuclei are stained in blue with DAPI.
Scale bars = 5 μm, unless indicated otherwise on the picture. |
