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Rho GTPase and Shroom direct planar polarized actomyosin contractility during convergent extension.

Simões Sde M, Mainieri A, Zallen JA - J. Cell Biol. (2014)

Bottom Line: Shroom, an asymmetrically localized actin- and Rho-kinase-binding protein, amplifies Rho-kinase and myosin II planar polarity and junctional localization downstream of Rho signaling.In Shroom mutants, Rho-kinase and myosin II achieve reduced levels of planar polarity, resulting in decreased junctional tension, a disruption of multicellular rosette formation, and defective convergent extension.These results indicate that Rho GTPase activity is required to establish a planar polarized actomyosin network, and the Shroom actin-binding protein enhances myosin contractility locally to generate robust mechanical forces during axis elongation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Howard Hughes Medical Institute and 2 Developmental Biology Program, Sloan Kettering Institute, New York, NY 10065.

ABSTRACT
Actomyosin contraction generates mechanical forces that influence cell and tissue structure. During convergent extension in Drosophila melanogaster, the spatially regulated activity of the myosin activator Rho-kinase promotes actomyosin contraction at specific planar cell boundaries to produce polarized cell rearrangement. The mechanisms that direct localized Rho-kinase activity are not well understood. We show that Rho GTPase recruits Rho-kinase to adherens junctions and is required for Rho-kinase planar polarity. Shroom, an asymmetrically localized actin- and Rho-kinase-binding protein, amplifies Rho-kinase and myosin II planar polarity and junctional localization downstream of Rho signaling. In Shroom mutants, Rho-kinase and myosin II achieve reduced levels of planar polarity, resulting in decreased junctional tension, a disruption of multicellular rosette formation, and defective convergent extension. These results indicate that Rho GTPase activity is required to establish a planar polarized actomyosin network, and the Shroom actin-binding protein enhances myosin contractility locally to generate robust mechanical forces during axis elongation.

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The Shroom actin-binding protein is planar polarized in intercalating cells. (A and B) Localization of Shroom (A–B) and Baz/Par-3 (A′ and B) in wild-type embryos at the indicated stages. (A) Anterior is left, and ventral is down. (B) Cross section of a stage 8 embryo, with apical up. (C) Planar polarized enrichment of Shroom at AP cell boundaries (75–90° with respect to the AP axis) relative to DV cell boundaries (0–15°). (D) Planar polarized enrichment of Par-3 at DV cell boundaries relative to AP cell boundaries at the indicated stages. Note that Shroom planar polarity appears later than Par-3. A single value was obtained for each image by averaging 100–200 edges/image; 5–13 images in 2–7 embryos were analyzed/stage, except early stage 6 (three images in one embryo). Means ± SEM between images are shown. Bars, 10 µm.
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fig3: The Shroom actin-binding protein is planar polarized in intercalating cells. (A and B) Localization of Shroom (A–B) and Baz/Par-3 (A′ and B) in wild-type embryos at the indicated stages. (A) Anterior is left, and ventral is down. (B) Cross section of a stage 8 embryo, with apical up. (C) Planar polarized enrichment of Shroom at AP cell boundaries (75–90° with respect to the AP axis) relative to DV cell boundaries (0–15°). (D) Planar polarized enrichment of Par-3 at DV cell boundaries relative to AP cell boundaries at the indicated stages. Note that Shroom planar polarity appears later than Par-3. A single value was obtained for each image by averaging 100–200 edges/image; 5–13 images in 2–7 embryos were analyzed/stage, except early stage 6 (three images in one embryo). Means ± SEM between images are shown. Bars, 10 µm.

Mentions: Because the SB domain is required for Rho-kinase planar polarity, we hypothesized that Shroom enhances Rho-kinase planar polarity downstream of a subtle asymmetry in Rho signaling. To investigate this possibility, we analyzed the localization of ShrmA, the predominant Shroom isoform in the Drosophila embryo. Shroom localizes to adherens junctions at three-cell vertices before axis elongation (Fig. 3 A, stage 6), consistent with a previous study (Bolinger et al., 2010). In addition, we found that Shroom has a striking planar polarized distribution during axis elongation. During stages 7 and 8, when cells undergo active cell rearrangement, Shroom was strongly enriched in adherens junctions at AP interfaces, colocalizing with Rho-kinase and myosin II (Fig. 3, A–C). In contrast to the Baz/Par-3 junctional protein, which is enriched in the complementary domain in stage 6 before elongation (Blankenship et al., 2006), Shroom planar polarity was most evident during cell rearrangement in stage 7 (Fig. 3, C and D). This distribution is consistent with a potential role for Shroom in regulating planar polarity during axis elongation.


Rho GTPase and Shroom direct planar polarized actomyosin contractility during convergent extension.

Simões Sde M, Mainieri A, Zallen JA - J. Cell Biol. (2014)

The Shroom actin-binding protein is planar polarized in intercalating cells. (A and B) Localization of Shroom (A–B) and Baz/Par-3 (A′ and B) in wild-type embryos at the indicated stages. (A) Anterior is left, and ventral is down. (B) Cross section of a stage 8 embryo, with apical up. (C) Planar polarized enrichment of Shroom at AP cell boundaries (75–90° with respect to the AP axis) relative to DV cell boundaries (0–15°). (D) Planar polarized enrichment of Par-3 at DV cell boundaries relative to AP cell boundaries at the indicated stages. Note that Shroom planar polarity appears later than Par-3. A single value was obtained for each image by averaging 100–200 edges/image; 5–13 images in 2–7 embryos were analyzed/stage, except early stage 6 (three images in one embryo). Means ± SEM between images are shown. Bars, 10 µm.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3926966&req=5

fig3: The Shroom actin-binding protein is planar polarized in intercalating cells. (A and B) Localization of Shroom (A–B) and Baz/Par-3 (A′ and B) in wild-type embryos at the indicated stages. (A) Anterior is left, and ventral is down. (B) Cross section of a stage 8 embryo, with apical up. (C) Planar polarized enrichment of Shroom at AP cell boundaries (75–90° with respect to the AP axis) relative to DV cell boundaries (0–15°). (D) Planar polarized enrichment of Par-3 at DV cell boundaries relative to AP cell boundaries at the indicated stages. Note that Shroom planar polarity appears later than Par-3. A single value was obtained for each image by averaging 100–200 edges/image; 5–13 images in 2–7 embryos were analyzed/stage, except early stage 6 (three images in one embryo). Means ± SEM between images are shown. Bars, 10 µm.
Mentions: Because the SB domain is required for Rho-kinase planar polarity, we hypothesized that Shroom enhances Rho-kinase planar polarity downstream of a subtle asymmetry in Rho signaling. To investigate this possibility, we analyzed the localization of ShrmA, the predominant Shroom isoform in the Drosophila embryo. Shroom localizes to adherens junctions at three-cell vertices before axis elongation (Fig. 3 A, stage 6), consistent with a previous study (Bolinger et al., 2010). In addition, we found that Shroom has a striking planar polarized distribution during axis elongation. During stages 7 and 8, when cells undergo active cell rearrangement, Shroom was strongly enriched in adherens junctions at AP interfaces, colocalizing with Rho-kinase and myosin II (Fig. 3, A–C). In contrast to the Baz/Par-3 junctional protein, which is enriched in the complementary domain in stage 6 before elongation (Blankenship et al., 2006), Shroom planar polarity was most evident during cell rearrangement in stage 7 (Fig. 3, C and D). This distribution is consistent with a potential role for Shroom in regulating planar polarity during axis elongation.

Bottom Line: Shroom, an asymmetrically localized actin- and Rho-kinase-binding protein, amplifies Rho-kinase and myosin II planar polarity and junctional localization downstream of Rho signaling.In Shroom mutants, Rho-kinase and myosin II achieve reduced levels of planar polarity, resulting in decreased junctional tension, a disruption of multicellular rosette formation, and defective convergent extension.These results indicate that Rho GTPase activity is required to establish a planar polarized actomyosin network, and the Shroom actin-binding protein enhances myosin contractility locally to generate robust mechanical forces during axis elongation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Howard Hughes Medical Institute and 2 Developmental Biology Program, Sloan Kettering Institute, New York, NY 10065.

ABSTRACT
Actomyosin contraction generates mechanical forces that influence cell and tissue structure. During convergent extension in Drosophila melanogaster, the spatially regulated activity of the myosin activator Rho-kinase promotes actomyosin contraction at specific planar cell boundaries to produce polarized cell rearrangement. The mechanisms that direct localized Rho-kinase activity are not well understood. We show that Rho GTPase recruits Rho-kinase to adherens junctions and is required for Rho-kinase planar polarity. Shroom, an asymmetrically localized actin- and Rho-kinase-binding protein, amplifies Rho-kinase and myosin II planar polarity and junctional localization downstream of Rho signaling. In Shroom mutants, Rho-kinase and myosin II achieve reduced levels of planar polarity, resulting in decreased junctional tension, a disruption of multicellular rosette formation, and defective convergent extension. These results indicate that Rho GTPase activity is required to establish a planar polarized actomyosin network, and the Shroom actin-binding protein enhances myosin contractility locally to generate robust mechanical forces during axis elongation.

Show MeSH
Related in: MedlinePlus