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An outer arm Dynein conformational switch is required for metachronal synchrony of motile cilia in planaria.

Rompolas P, Patel-King RS, King SM - Mol. Biol. Cell (2010)

Bottom Line: The lack of metachrony was not due simply to a decrease in ciliary beat frequency, as reducing this parameter by altering medium viscosity did not affect ciliary coordination.In addition, we did not observe a significant temporal variability in the beat cycle of impaired cilia.We propose that this conformational switch provides a mechanical feedback system within outer arm dynein that is necessary to entrain metachronal synchrony.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, Farmington, CT 06030-3305, USA.

ABSTRACT
Motile cilia mediate the flow of mucus and other fluids across the surface of specialized epithelia in metazoans. Efficient clearance of peri-ciliary fluids depends on the precise coordination of ciliary beating to produce metachronal waves. The role of individual dynein motors and the mechanical feedback mechanisms required for this process are not well understood. Here we used the ciliated epithelium of the planarian Schmidtea mediterranea to dissect the role of outer arm dynein motors in the metachronal synchrony of motile cilia. We demonstrate that animals that completely lack outer dynein arms display a significant decline in beat frequency and an inability of cilia to coordinate their oscillations and form metachronal waves. Furthermore, lack of a key mechanosensitive regulatory component (LC1) yields a similar phenotype even though outer arms still assemble in the axoneme. The lack of metachrony was not due simply to a decrease in ciliary beat frequency, as reducing this parameter by altering medium viscosity did not affect ciliary coordination. In addition, we did not observe a significant temporal variability in the beat cycle of impaired cilia. We propose that this conformational switch provides a mechanical feedback system within outer arm dynein that is necessary to entrain metachronal synchrony.

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Physical properties of planarian ciliary motility. Assessment of planarian ciliary beat frequency and waveform by high-speed video microscopy captured at 250 frames/s using DIC optics. (a) Sequential frames (4 ms apart) of planaria cilia undergoing a single beat cycle. Cilia complete a full beat cycle in 35–45 ms (∼24 Hz; also see Movie S1). Neighboring cilia synchronize their beating and form metachronal waves that are propagated along the plane of the ciliary beat. (b) Kymograph from the decompiled video of beating cilia over a 1-s period, illustrating 24 successive ciliary beat cycles. (c) Traces of a single cilium depicting its position at 4-ms intervals during a complete beat cycle. Planarian cilia beat with an asymmetric waveform consisting of an effective and a recovery stroke; the effective stroke is completed in ∼15 ms representing one-third of the ciliary beat cycle. (d) A single video frame depicting the formation of metachronal waves from the coordination of neighboring cilia. The wavelength of the metachronal wave is ∼50 μm.
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Figure 3: Physical properties of planarian ciliary motility. Assessment of planarian ciliary beat frequency and waveform by high-speed video microscopy captured at 250 frames/s using DIC optics. (a) Sequential frames (4 ms apart) of planaria cilia undergoing a single beat cycle. Cilia complete a full beat cycle in 35–45 ms (∼24 Hz; also see Movie S1). Neighboring cilia synchronize their beating and form metachronal waves that are propagated along the plane of the ciliary beat. (b) Kymograph from the decompiled video of beating cilia over a 1-s period, illustrating 24 successive ciliary beat cycles. (c) Traces of a single cilium depicting its position at 4-ms intervals during a complete beat cycle. Planarian cilia beat with an asymmetric waveform consisting of an effective and a recovery stroke; the effective stroke is completed in ∼15 ms representing one-third of the ciliary beat cycle. (d) A single video frame depicting the formation of metachronal waves from the coordination of neighboring cilia. The wavelength of the metachronal wave is ∼50 μm.

Mentions: To investigate the physical properties of planarian ciliary motility, we used high-speed video microscopy to visualize the cilia on the lateral sides of the head. We found that all cilia are motile and beat continuously even when the animal is stationary. Analysis of sequential frames from movies captured at 250 frames per second, revealed that the duration of a complete beat cycle is ∼35–45 ms, which represents a CBF of ∼24 Hz (Figure 3, a and b; Movie S1). The ciliary waveform is highly asymmetric, consisting of an effective and a recovery stroke (Figure 3c), similar to the waveform of cilia in epithelia from other organisms. The effective stroke represents one-third of the beat cycle and takes ∼15 ms to complete, with the recovery stroke lasting for ∼25 ms. Planarian ventral cilia beat in a coordinated manner and form metachronal waves with a mean wavelength of ∼50 μm (Figure 3d), that are propagated along the direction of the effective stroke. All the cilia that we were able to visualize live, mostly around the head region, orient their beating along the same axis with the effective stroke directed toward the tail; this is consistent with their proposed role in driving gliding locomotion.


An outer arm Dynein conformational switch is required for metachronal synchrony of motile cilia in planaria.

Rompolas P, Patel-King RS, King SM - Mol. Biol. Cell (2010)

Physical properties of planarian ciliary motility. Assessment of planarian ciliary beat frequency and waveform by high-speed video microscopy captured at 250 frames/s using DIC optics. (a) Sequential frames (4 ms apart) of planaria cilia undergoing a single beat cycle. Cilia complete a full beat cycle in 35–45 ms (∼24 Hz; also see Movie S1). Neighboring cilia synchronize their beating and form metachronal waves that are propagated along the plane of the ciliary beat. (b) Kymograph from the decompiled video of beating cilia over a 1-s period, illustrating 24 successive ciliary beat cycles. (c) Traces of a single cilium depicting its position at 4-ms intervals during a complete beat cycle. Planarian cilia beat with an asymmetric waveform consisting of an effective and a recovery stroke; the effective stroke is completed in ∼15 ms representing one-third of the ciliary beat cycle. (d) A single video frame depicting the formation of metachronal waves from the coordination of neighboring cilia. The wavelength of the metachronal wave is ∼50 μm.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC2965684&req=5

Figure 3: Physical properties of planarian ciliary motility. Assessment of planarian ciliary beat frequency and waveform by high-speed video microscopy captured at 250 frames/s using DIC optics. (a) Sequential frames (4 ms apart) of planaria cilia undergoing a single beat cycle. Cilia complete a full beat cycle in 35–45 ms (∼24 Hz; also see Movie S1). Neighboring cilia synchronize their beating and form metachronal waves that are propagated along the plane of the ciliary beat. (b) Kymograph from the decompiled video of beating cilia over a 1-s period, illustrating 24 successive ciliary beat cycles. (c) Traces of a single cilium depicting its position at 4-ms intervals during a complete beat cycle. Planarian cilia beat with an asymmetric waveform consisting of an effective and a recovery stroke; the effective stroke is completed in ∼15 ms representing one-third of the ciliary beat cycle. (d) A single video frame depicting the formation of metachronal waves from the coordination of neighboring cilia. The wavelength of the metachronal wave is ∼50 μm.
Mentions: To investigate the physical properties of planarian ciliary motility, we used high-speed video microscopy to visualize the cilia on the lateral sides of the head. We found that all cilia are motile and beat continuously even when the animal is stationary. Analysis of sequential frames from movies captured at 250 frames per second, revealed that the duration of a complete beat cycle is ∼35–45 ms, which represents a CBF of ∼24 Hz (Figure 3, a and b; Movie S1). The ciliary waveform is highly asymmetric, consisting of an effective and a recovery stroke (Figure 3c), similar to the waveform of cilia in epithelia from other organisms. The effective stroke represents one-third of the beat cycle and takes ∼15 ms to complete, with the recovery stroke lasting for ∼25 ms. Planarian ventral cilia beat in a coordinated manner and form metachronal waves with a mean wavelength of ∼50 μm (Figure 3d), that are propagated along the direction of the effective stroke. All the cilia that we were able to visualize live, mostly around the head region, orient their beating along the same axis with the effective stroke directed toward the tail; this is consistent with their proposed role in driving gliding locomotion.

Bottom Line: The lack of metachrony was not due simply to a decrease in ciliary beat frequency, as reducing this parameter by altering medium viscosity did not affect ciliary coordination.In addition, we did not observe a significant temporal variability in the beat cycle of impaired cilia.We propose that this conformational switch provides a mechanical feedback system within outer arm dynein that is necessary to entrain metachronal synchrony.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, Farmington, CT 06030-3305, USA.

ABSTRACT
Motile cilia mediate the flow of mucus and other fluids across the surface of specialized epithelia in metazoans. Efficient clearance of peri-ciliary fluids depends on the precise coordination of ciliary beating to produce metachronal waves. The role of individual dynein motors and the mechanical feedback mechanisms required for this process are not well understood. Here we used the ciliated epithelium of the planarian Schmidtea mediterranea to dissect the role of outer arm dynein motors in the metachronal synchrony of motile cilia. We demonstrate that animals that completely lack outer dynein arms display a significant decline in beat frequency and an inability of cilia to coordinate their oscillations and form metachronal waves. Furthermore, lack of a key mechanosensitive regulatory component (LC1) yields a similar phenotype even though outer arms still assemble in the axoneme. The lack of metachrony was not due simply to a decrease in ciliary beat frequency, as reducing this parameter by altering medium viscosity did not affect ciliary coordination. In addition, we did not observe a significant temporal variability in the beat cycle of impaired cilia. We propose that this conformational switch provides a mechanical feedback system within outer arm dynein that is necessary to entrain metachronal synchrony.

Show MeSH
Related in: MedlinePlus