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Myosin light-chain phosphatase regulates basal actomyosin oscillations during morphogenesis.

Valencia-Expósito A, Grosheva I, Míguez DG, González-Reyes A, Martín-Bermudo MD - Nat Commun (2016)

Bottom Line: Contractile actomyosin networks generate forces that drive tissue morphogenesis.While the role of myosin light-chain kinase in regulating contractility during morphogenesis has been largely characterized, there is surprisingly little information on myosin light-chain phosphatase (MLCP) function in this context.Contrary to previous reports, basal F-actin pulsates similarly to myosin.

View Article: PubMed Central - PubMed

Affiliation: Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide/CSIC/JA, Carretera de Utrera km 1, Sevilla 41013, Spain.

ABSTRACT
Contractile actomyosin networks generate forces that drive tissue morphogenesis. Actomyosin contractility is controlled primarily by reversible phosphorylation of the myosin-II regulatory light chain through the action of myosin kinases and phosphatases. While the role of myosin light-chain kinase in regulating contractility during morphogenesis has been largely characterized, there is surprisingly little information on myosin light-chain phosphatase (MLCP) function in this context. Here, we use live imaging of Drosophila follicle cells combined with mathematical modelling to demonstrate that the MLCP subunit flapwing (flw) is a key regulator of basal myosin oscillations and cell contractions underlying egg chamber elongation. Flw expression decreases specifically on the basal side of follicle cells at the onset of contraction and flw controls the initiation and periodicity of basal actomyosin oscillations. Contrary to previous reports, basal F-actin pulsates similarly to myosin. Finally, we propose a quantitative model in which periodic basal actomyosin oscillations arise in a cell-autonomous fashion from intrinsic properties of motor assemblies.

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Related in: MedlinePlus

Loss of flw results in both precocious basal myosin oscillations and increased basal contractility.(a) Confocal images taken with a 5-min difference of a live S6 mosaic egg chamber expressing Sqh-GFP (green) and carrying flw mutant clones identified by the absence of nuclear mCherry (red). While the levels of Sqh-GFP in flw mutant FCs are high and oscillate (arrows), control cells show low and constant Sqh-GFP amounts. (b) Quantification of the dynamic changes of Sqh-GFP in one of the above control cells (light green line) and two flw mutants (purple line). (c,d) Quantification of cell elongation after photoablation at the basal (c) and apical (d) domains of control (n=52) and flw (n=56) mutant FCs in six independently cultured egg chambers. %Δl=100x(L−l)/l where l is the original distance between the cell vertices associated to the ablated edge and L is the distance 10 sec. after photoablation. Scale bar: 10 μm. Mean of n>30 FCs, assessed over 9 independent experiments.
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f3: Loss of flw results in both precocious basal myosin oscillations and increased basal contractility.(a) Confocal images taken with a 5-min difference of a live S6 mosaic egg chamber expressing Sqh-GFP (green) and carrying flw mutant clones identified by the absence of nuclear mCherry (red). While the levels of Sqh-GFP in flw mutant FCs are high and oscillate (arrows), control cells show low and constant Sqh-GFP amounts. (b) Quantification of the dynamic changes of Sqh-GFP in one of the above control cells (light green line) and two flw mutants (purple line). (c,d) Quantification of cell elongation after photoablation at the basal (c) and apical (d) domains of control (n=52) and flw (n=56) mutant FCs in six independently cultured egg chambers. %Δl=100x(L−l)/l where l is the original distance between the cell vertices associated to the ablated edge and L is the distance 10 sec. after photoablation. Scale bar: 10 μm. Mean of n>30 FCs, assessed over 9 independent experiments.

Mentions: A characteristic feature of the basal contractile arrays formed in S9–S10 wild-type FCs is the periodic changes in myosin concentration8. To test if the elevated levels of basal myosin found in early-stage flw mutant FCs underwent a similar oscillatory behaviour, we performed live imaging of mosaic S6 egg chambers expressing Sqh-GFP and containing flw mutant FCs (nine egg chambers cultured independently on different days were analysed). We found that basal myosin in mutant cells (n=30) underwent periodic fluctuations (Fig. 3a,b; Supplementary Movie 1). However, in contrast to the marked and periodic changes in basal myosin levels found in S9–S10 control FCs8 (n=34, Supplementary Movie 2), the oscillation period in S6 flw mutant FCs showed a high degree of variability (Fig. 3b), suggesting that flw regulated not only the initiation of myosin oscillation but also its periodicity.


Myosin light-chain phosphatase regulates basal actomyosin oscillations during morphogenesis.

Valencia-Expósito A, Grosheva I, Míguez DG, González-Reyes A, Martín-Bermudo MD - Nat Commun (2016)

Loss of flw results in both precocious basal myosin oscillations and increased basal contractility.(a) Confocal images taken with a 5-min difference of a live S6 mosaic egg chamber expressing Sqh-GFP (green) and carrying flw mutant clones identified by the absence of nuclear mCherry (red). While the levels of Sqh-GFP in flw mutant FCs are high and oscillate (arrows), control cells show low and constant Sqh-GFP amounts. (b) Quantification of the dynamic changes of Sqh-GFP in one of the above control cells (light green line) and two flw mutants (purple line). (c,d) Quantification of cell elongation after photoablation at the basal (c) and apical (d) domains of control (n=52) and flw (n=56) mutant FCs in six independently cultured egg chambers. %Δl=100x(L−l)/l where l is the original distance between the cell vertices associated to the ablated edge and L is the distance 10 sec. after photoablation. Scale bar: 10 μm. Mean of n>30 FCs, assessed over 9 independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4759631&req=5

f3: Loss of flw results in both precocious basal myosin oscillations and increased basal contractility.(a) Confocal images taken with a 5-min difference of a live S6 mosaic egg chamber expressing Sqh-GFP (green) and carrying flw mutant clones identified by the absence of nuclear mCherry (red). While the levels of Sqh-GFP in flw mutant FCs are high and oscillate (arrows), control cells show low and constant Sqh-GFP amounts. (b) Quantification of the dynamic changes of Sqh-GFP in one of the above control cells (light green line) and two flw mutants (purple line). (c,d) Quantification of cell elongation after photoablation at the basal (c) and apical (d) domains of control (n=52) and flw (n=56) mutant FCs in six independently cultured egg chambers. %Δl=100x(L−l)/l where l is the original distance between the cell vertices associated to the ablated edge and L is the distance 10 sec. after photoablation. Scale bar: 10 μm. Mean of n>30 FCs, assessed over 9 independent experiments.
Mentions: A characteristic feature of the basal contractile arrays formed in S9–S10 wild-type FCs is the periodic changes in myosin concentration8. To test if the elevated levels of basal myosin found in early-stage flw mutant FCs underwent a similar oscillatory behaviour, we performed live imaging of mosaic S6 egg chambers expressing Sqh-GFP and containing flw mutant FCs (nine egg chambers cultured independently on different days were analysed). We found that basal myosin in mutant cells (n=30) underwent periodic fluctuations (Fig. 3a,b; Supplementary Movie 1). However, in contrast to the marked and periodic changes in basal myosin levels found in S9–S10 control FCs8 (n=34, Supplementary Movie 2), the oscillation period in S6 flw mutant FCs showed a high degree of variability (Fig. 3b), suggesting that flw regulated not only the initiation of myosin oscillation but also its periodicity.

Bottom Line: Contractile actomyosin networks generate forces that drive tissue morphogenesis.While the role of myosin light-chain kinase in regulating contractility during morphogenesis has been largely characterized, there is surprisingly little information on myosin light-chain phosphatase (MLCP) function in this context.Contrary to previous reports, basal F-actin pulsates similarly to myosin.

View Article: PubMed Central - PubMed

Affiliation: Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide/CSIC/JA, Carretera de Utrera km 1, Sevilla 41013, Spain.

ABSTRACT
Contractile actomyosin networks generate forces that drive tissue morphogenesis. Actomyosin contractility is controlled primarily by reversible phosphorylation of the myosin-II regulatory light chain through the action of myosin kinases and phosphatases. While the role of myosin light-chain kinase in regulating contractility during morphogenesis has been largely characterized, there is surprisingly little information on myosin light-chain phosphatase (MLCP) function in this context. Here, we use live imaging of Drosophila follicle cells combined with mathematical modelling to demonstrate that the MLCP subunit flapwing (flw) is a key regulator of basal myosin oscillations and cell contractions underlying egg chamber elongation. Flw expression decreases specifically on the basal side of follicle cells at the onset of contraction and flw controls the initiation and periodicity of basal actomyosin oscillations. Contrary to previous reports, basal F-actin pulsates similarly to myosin. Finally, we propose a quantitative model in which periodic basal actomyosin oscillations arise in a cell-autonomous fashion from intrinsic properties of motor assemblies.

Show MeSH
Related in: MedlinePlus