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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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S. mediterranea: an experimental model for ciliated epithelia. (a) A typical S. mediterranea adult flatworm used in this study. (b) Cross section of paraffin-embedded planarian tissue counterstained with hematoxylin and eosin. Dorsoventral muscle bands (mb) divide the body into compartments that are traversed by branches of the gastrovascular (gv) cavity. The mesenchyme (me) of the planarian body is populated with numerous undifferentiated pluripotent cells, known as neoblasts. The epidermis consists of a simple cuboidal epithelium, composed of ciliated (ventral) or mostly nonciliated (dorsal) cells. Dispersed throughout the epithelium are secretory ducts (SD) and rhabdites (rhb); rhabdites in the dorsal surface appear larger in size. (c) Dorsal view of a live planarian. Motile cilia are readily visible on the lateral sides of the head region. The inset at right shows a magnified area of the left lateral side of the head where a row of cilia may be seen.
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Figure 1: S. mediterranea: an experimental model for ciliated epithelia. (a) A typical S. mediterranea adult flatworm used in this study. (b) Cross section of paraffin-embedded planarian tissue counterstained with hematoxylin and eosin. Dorsoventral muscle bands (mb) divide the body into compartments that are traversed by branches of the gastrovascular (gv) cavity. The mesenchyme (me) of the planarian body is populated with numerous undifferentiated pluripotent cells, known as neoblasts. The epidermis consists of a simple cuboidal epithelium, composed of ciliated (ventral) or mostly nonciliated (dorsal) cells. Dispersed throughout the epithelium are secretory ducts (SD) and rhabdites (rhb); rhabdites in the dorsal surface appear larger in size. (c) Dorsal view of a live planarian. Motile cilia are readily visible on the lateral sides of the head region. The inset at right shows a magnified area of the left lateral side of the head where a row of cilia may be seen.

Mentions: S. mediterranea has been used extensively in recent years for research into stem cell biology and regeneration due in part to a sequenced genome and genetic tractability (Newmark and Sánchez Alvarado, 2002). To evaluate the use of S. mediterranea (Figure 1a) as an experimental model for the study of ciliary motility and the mechanisms of metachronal synchrony in a multiciliated epithelium, we initially characterized the structure and distribution of the cilia and investigated the role of these organelles in planarian physiology. The epithelium surrounding the planarian body is simple cuboidal with the nuclei of the cell monolayer aligned on a single level and in close proximity to the basal lamina (Figure 1b). We observed distinctive differences between the dorsal and ventral regions of the planarian epithelium. Cells on the ventral surface are cubical in shape and possess multiple motile cilia in contrast to the cells on the dorsal surface that are mostly nonciliated and more columnar (Figure 1b). Also present in the epithelium are rhabdites and secretory ducts that extend through the basement lamina to the epidermis from parenchymal secretory cells, as described previously (Bowen and Ryder, 1974; Hori, 1978). These structures secrete the mucus layer on which the flatworm is able to glide (Martin, 1978). The border between the ciliated and nonciliated epidermis extends to the lateral sides of the planarian body allowing several rows of cilia to be visible when the animal is viewed from the top (Figure 1c).


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)

S. mediterranea: an experimental model for ciliated epithelia. (a) A typical S. mediterranea adult flatworm used in this study. (b) Cross section of paraffin-embedded planarian tissue counterstained with hematoxylin and eosin. Dorsoventral muscle bands (mb) divide the body into compartments that are traversed by branches of the gastrovascular (gv) cavity. The mesenchyme (me) of the planarian body is populated with numerous undifferentiated pluripotent cells, known as neoblasts. The epidermis consists of a simple cuboidal epithelium, composed of ciliated (ventral) or mostly nonciliated (dorsal) cells. Dispersed throughout the epithelium are secretory ducts (SD) and rhabdites (rhb); rhabdites in the dorsal surface appear larger in size. (c) Dorsal view of a live planarian. Motile cilia are readily visible on the lateral sides of the head region. The inset at right shows a magnified area of the left lateral side of the head where a row of cilia may be seen.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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

Figure 1: S. mediterranea: an experimental model for ciliated epithelia. (a) A typical S. mediterranea adult flatworm used in this study. (b) Cross section of paraffin-embedded planarian tissue counterstained with hematoxylin and eosin. Dorsoventral muscle bands (mb) divide the body into compartments that are traversed by branches of the gastrovascular (gv) cavity. The mesenchyme (me) of the planarian body is populated with numerous undifferentiated pluripotent cells, known as neoblasts. The epidermis consists of a simple cuboidal epithelium, composed of ciliated (ventral) or mostly nonciliated (dorsal) cells. Dispersed throughout the epithelium are secretory ducts (SD) and rhabdites (rhb); rhabdites in the dorsal surface appear larger in size. (c) Dorsal view of a live planarian. Motile cilia are readily visible on the lateral sides of the head region. The inset at right shows a magnified area of the left lateral side of the head where a row of cilia may be seen.
Mentions: S. mediterranea has been used extensively in recent years for research into stem cell biology and regeneration due in part to a sequenced genome and genetic tractability (Newmark and Sánchez Alvarado, 2002). To evaluate the use of S. mediterranea (Figure 1a) as an experimental model for the study of ciliary motility and the mechanisms of metachronal synchrony in a multiciliated epithelium, we initially characterized the structure and distribution of the cilia and investigated the role of these organelles in planarian physiology. The epithelium surrounding the planarian body is simple cuboidal with the nuclei of the cell monolayer aligned on a single level and in close proximity to the basal lamina (Figure 1b). We observed distinctive differences between the dorsal and ventral regions of the planarian epithelium. Cells on the ventral surface are cubical in shape and possess multiple motile cilia in contrast to the cells on the dorsal surface that are mostly nonciliated and more columnar (Figure 1b). Also present in the epithelium are rhabdites and secretory ducts that extend through the basement lamina to the epidermis from parenchymal secretory cells, as described previously (Bowen and Ryder, 1974; Hori, 1978). These structures secrete the mucus layer on which the flatworm is able to glide (Martin, 1978). The border between the ciliated and nonciliated epidermis extends to the lateral sides of the planarian body allowing several rows of cilia to be visible when the animal is viewed from the top (Figure 1c).

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