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The Rho GTPase Cdc42 regulates hair cell planar polarity and cellular patterning in the developing cochlea.

Kirjavainen A, Laos M, Anttonen T, Pirvola U - Biol Open (2015)

Bottom Line: Atypical protein kinase C (aPKC), a putative Cdc42 effector, colocalized with Cdc42 at the hair cell apex, and aPKC expression was altered upon Cdc42 depletion.Our data suggest that Cdc42 together with aPKC is part of the machinery establishing hair cell planar polarity and that Cdc42 acts on polarity through the cell-surface microtubule network.In addition, our data demonstrates that Cdc42 is required for stereociliogenesis in the immature cochlea.

View Article: PubMed Central - PubMed

Affiliation: Department of Biosciences, Viikinkaari 1, 00014 University of Helsinki, Finland.

No MeSH data available.


Disturbances in stereociliary bundle morphology, but maintained Rab11a expression in outer hair cells of Cdc42loxP/loxP;Fgfr3-iCre-ERT2 mice.(A) Confocal view of a whole mount specimen from the medial part of the control cochlea at E18.5 shows Rab11 expression close to the vertices of phalloidin-labeled hair bundles. (B,C) Both in the medial and basal coil of the mutant cochlea, Rab11 is expressed similarly as in the control specimen. (D,D′) Higher magnification view of the boxed area in C shows partial colocalization of acetylated tubulin, a kinocilium marker, and Rab11 at the base of kinocilia. This colocalization is best revealed in transverse plane (D′). A part of OHCs in this mutant specimen show dysmorphic bundles accompanied by off-centered kinocilia (arrows). Note that bundle dysmorphology exists also in normally oriented OHCs (asterisk). (E,F) SBEM images of OHC stereociliary bundles of control and mutant cochleas at E18.5. In the control specimen, kinocilium (red dot) is located at the vertex of the V-shaped hair bundle. In the mutant specimen, kinocilium is misplaced and the bundle is dysmorphic, with no clear vertex. (G) Also transverse sections immunohistochemically stained for Rab11 demonstrate expression in the apex of OHCs. Abbreviations: OHC, outer hair cell; IHC, inner hair cell. Scale bar shown in G: A–D″, G, 5 µm; E,F, 1 µm.
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f06: Disturbances in stereociliary bundle morphology, but maintained Rab11a expression in outer hair cells of Cdc42loxP/loxP;Fgfr3-iCre-ERT2 mice.(A) Confocal view of a whole mount specimen from the medial part of the control cochlea at E18.5 shows Rab11 expression close to the vertices of phalloidin-labeled hair bundles. (B,C) Both in the medial and basal coil of the mutant cochlea, Rab11 is expressed similarly as in the control specimen. (D,D′) Higher magnification view of the boxed area in C shows partial colocalization of acetylated tubulin, a kinocilium marker, and Rab11 at the base of kinocilia. This colocalization is best revealed in transverse plane (D′). A part of OHCs in this mutant specimen show dysmorphic bundles accompanied by off-centered kinocilia (arrows). Note that bundle dysmorphology exists also in normally oriented OHCs (asterisk). (E,F) SBEM images of OHC stereociliary bundles of control and mutant cochleas at E18.5. In the control specimen, kinocilium (red dot) is located at the vertex of the V-shaped hair bundle. In the mutant specimen, kinocilium is misplaced and the bundle is dysmorphic, with no clear vertex. (G) Also transverse sections immunohistochemically stained for Rab11 demonstrate expression in the apex of OHCs. Abbreviations: OHC, outer hair cell; IHC, inner hair cell. Scale bar shown in G: A–D″, G, 5 µm; E,F, 1 µm.

Mentions: In OHCs of the mutant mice, phalloidin labeling demonstrated dysmorphic hair bundles. In most cases, bundles were misoriented as well (Fig. 6A–D), but dysmorphic bundles lacking an orientation defect were also found (Fig. 6C,D). Abnormal bundle morphology, a read-out of altered hair cell intrinsic polarity (Sipe and Lu, 2011; Fukuda et al., 2014), was manifested as flat, wavy or inverted shape, often with no clear vertex. Importantly, bundle dysmorphology was often associated with abnormal positioning of the kinocilium relative to the bundle, as revealed by using acetylated tubulin as a kinocilium marker (Fig. 6C–D″). These findings were ultrastructurally confirmed by SBEM (Fig. 6E,F).


The Rho GTPase Cdc42 regulates hair cell planar polarity and cellular patterning in the developing cochlea.

Kirjavainen A, Laos M, Anttonen T, Pirvola U - Biol Open (2015)

Disturbances in stereociliary bundle morphology, but maintained Rab11a expression in outer hair cells of Cdc42loxP/loxP;Fgfr3-iCre-ERT2 mice.(A) Confocal view of a whole mount specimen from the medial part of the control cochlea at E18.5 shows Rab11 expression close to the vertices of phalloidin-labeled hair bundles. (B,C) Both in the medial and basal coil of the mutant cochlea, Rab11 is expressed similarly as in the control specimen. (D,D′) Higher magnification view of the boxed area in C shows partial colocalization of acetylated tubulin, a kinocilium marker, and Rab11 at the base of kinocilia. This colocalization is best revealed in transverse plane (D′). A part of OHCs in this mutant specimen show dysmorphic bundles accompanied by off-centered kinocilia (arrows). Note that bundle dysmorphology exists also in normally oriented OHCs (asterisk). (E,F) SBEM images of OHC stereociliary bundles of control and mutant cochleas at E18.5. In the control specimen, kinocilium (red dot) is located at the vertex of the V-shaped hair bundle. In the mutant specimen, kinocilium is misplaced and the bundle is dysmorphic, with no clear vertex. (G) Also transverse sections immunohistochemically stained for Rab11 demonstrate expression in the apex of OHCs. Abbreviations: OHC, outer hair cell; IHC, inner hair cell. Scale bar shown in G: A–D″, G, 5 µm; E,F, 1 µm.
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Related In: Results  -  Collection

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f06: Disturbances in stereociliary bundle morphology, but maintained Rab11a expression in outer hair cells of Cdc42loxP/loxP;Fgfr3-iCre-ERT2 mice.(A) Confocal view of a whole mount specimen from the medial part of the control cochlea at E18.5 shows Rab11 expression close to the vertices of phalloidin-labeled hair bundles. (B,C) Both in the medial and basal coil of the mutant cochlea, Rab11 is expressed similarly as in the control specimen. (D,D′) Higher magnification view of the boxed area in C shows partial colocalization of acetylated tubulin, a kinocilium marker, and Rab11 at the base of kinocilia. This colocalization is best revealed in transverse plane (D′). A part of OHCs in this mutant specimen show dysmorphic bundles accompanied by off-centered kinocilia (arrows). Note that bundle dysmorphology exists also in normally oriented OHCs (asterisk). (E,F) SBEM images of OHC stereociliary bundles of control and mutant cochleas at E18.5. In the control specimen, kinocilium (red dot) is located at the vertex of the V-shaped hair bundle. In the mutant specimen, kinocilium is misplaced and the bundle is dysmorphic, with no clear vertex. (G) Also transverse sections immunohistochemically stained for Rab11 demonstrate expression in the apex of OHCs. Abbreviations: OHC, outer hair cell; IHC, inner hair cell. Scale bar shown in G: A–D″, G, 5 µm; E,F, 1 µm.
Mentions: In OHCs of the mutant mice, phalloidin labeling demonstrated dysmorphic hair bundles. In most cases, bundles were misoriented as well (Fig. 6A–D), but dysmorphic bundles lacking an orientation defect were also found (Fig. 6C,D). Abnormal bundle morphology, a read-out of altered hair cell intrinsic polarity (Sipe and Lu, 2011; Fukuda et al., 2014), was manifested as flat, wavy or inverted shape, often with no clear vertex. Importantly, bundle dysmorphology was often associated with abnormal positioning of the kinocilium relative to the bundle, as revealed by using acetylated tubulin as a kinocilium marker (Fig. 6C–D″). These findings were ultrastructurally confirmed by SBEM (Fig. 6E,F).

Bottom Line: Atypical protein kinase C (aPKC), a putative Cdc42 effector, colocalized with Cdc42 at the hair cell apex, and aPKC expression was altered upon Cdc42 depletion.Our data suggest that Cdc42 together with aPKC is part of the machinery establishing hair cell planar polarity and that Cdc42 acts on polarity through the cell-surface microtubule network.In addition, our data demonstrates that Cdc42 is required for stereociliogenesis in the immature cochlea.

View Article: PubMed Central - PubMed

Affiliation: Department of Biosciences, Viikinkaari 1, 00014 University of Helsinki, Finland.

No MeSH data available.