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Biological adhesion of the flatworm Macrostomum lignano relies on a duo-gland system and is mediated by a cell type-specific intermediate filament protein.

Lengerer B, Pjeta R, Wunderer J, Rodrigues M, Arbore R, Schärer L, Berezikov E, Hess MW, Pfaller K, Egger B, Obwegeser S, Salvenmoser W, Ladurner P - Front. Zool. (2014)

Bottom Line: About 130 adhesive organs are located in a horse-shoe-shaped arc along the ventral side of the tail plate.RNA interference mediated knock-down resulted in the first experimentally induced non-adhesion phenotype in any marine animal.Therefore, our current findings and future investigations using this powerful flatworm model system might contribute to a better understanding of the function of intermediate filaments and their associated human diseases.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Zoology and Center of Molecular Bioscience Innsbruck, University of Innsbruck, Technikerstr, 25, Innsbruck A-6020, Austria. peter.ladurner@uibk.ac.at.

ABSTRACT

Background: Free-living flatworms, in both marine and freshwater environments, are able to adhere to and release from a substrate several times within a second. This reversible adhesion relies on adhesive organs comprised of three cell types: an adhesive gland cell, a releasing gland cell, and an anchor cell, which is a modified epidermal cell responsible for structural support. However, nothing is currently known about the molecules that are involved in this adhesion process.

Results: In this study we present the detailed morphology of the adhesive organs of the free-living marine flatworm Macrostomum lignano. About 130 adhesive organs are located in a horse-shoe-shaped arc along the ventral side of the tail plate. Each organ consists of exactly three cells, an adhesive gland cell, a releasing gland cell, and an anchor cell. The necks of the two gland cells penetrate the anchor cell through a common pore. Modified microvilli of the anchor cell form a collar surrounding the necks of the adhesive- and releasing glands, jointly forming the papilla, the outer visible part of the adhesive organs. Next, we identified an intermediate filament (IF) gene, macif1, which is expressed in the anchor cells. RNA interference mediated knock-down resulted in the first experimentally induced non-adhesion phenotype in any marine animal. Specifically, the absence of intermediate filaments in the anchor cells led to papillae with open tips, a reduction of the cytoskeleton network, a decline in hemidesmosomal connections, and to shortened microvilli containing less actin.

Conclusion: Our findings reveal an elaborate biological adhesion system in a free-living flatworm, which permits impressively rapid temporary adhesion-release performance in the marine environment. We demonstrate that the structural integrity of the supportive cell, the anchor cell, is essential for this adhesion process: the knock-down of the anchor cell-specific intermediate filament gene resulted in the inability of the animals to adhere. The RNAi mediated changes of the anchor cell morphology are comparable to situations observed in human gut epithelia. Therefore, our current findings and future investigations using this powerful flatworm model system might contribute to a better understanding of the function of intermediate filaments and their associated human diseases.

No MeSH data available.


Related in: MedlinePlus

Overview and fine structure of the M. lignano adhesive organs. Schematic illustration (A) and transmission electron microscopy (cryo-processed specimens) (B-G). (A) Localization of adhesive organ cell types: anchor cell (blue); adhesive gland (red); releasing gland (green). The red line indicates the level of the cross section of the adhesive papilla. (B) Sagittal section of the tip of the M. lignano tail plate. Four adhesive organs are visible and several gland cell necks reach into the tail plate. (C) Sagittal section of an adhesive organ. Inset: detail of respective vesicle types. (D) Section showing strengthened adherens junctions (arrowheads) and septate junctions (arrows) between an epidermal cell and an anchor cell and between an adhesive cell and an anchor cell. Note: microtubules (mt) within the adhesive gland. (E) Basal cytoplasmic extension of an anchor cell (ac) with intermediate filaments (if); the cell is connected to the extracellular matrix (ecm) via a hemidesmosome (hd). (F) Horizontal section through adhesive organs and an epidermal cell (ep) with cilia (ci) and microvilli (mv) protruding from the epidermal surface. Three adhesive organs are sectioned at different levels. Note that the anchor cell (ac) surrounds the adhesive gland (ag) and releasing gland (rg) cells in a donut-shaped manner, i.e. without cytoplasmic interruption. (G) Cross section through an adhesive organ with central adhesive gland (ag) and releasing gland (rg) cells surrounded by a collar of microvilli of the anchor cell (acmv). ac anchor cell; acmv anchor cell microvilli; ag adhesive gland; ci cilium; ecm extracellular matrix; ep epidermis; hd hemidesmosome; if intermediate filaments; mt microtubules; mv microvilli of regular epidermal cells; rg releasing gland; rh rhabdite glands, ultrarhabdites (urh). Scale bars (A) 5 μm, (C,F) 1 μm, (D,E,G) 0.5 μm.
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Figure 3: Overview and fine structure of the M. lignano adhesive organs. Schematic illustration (A) and transmission electron microscopy (cryo-processed specimens) (B-G). (A) Localization of adhesive organ cell types: anchor cell (blue); adhesive gland (red); releasing gland (green). The red line indicates the level of the cross section of the adhesive papilla. (B) Sagittal section of the tip of the M. lignano tail plate. Four adhesive organs are visible and several gland cell necks reach into the tail plate. (C) Sagittal section of an adhesive organ. Inset: detail of respective vesicle types. (D) Section showing strengthened adherens junctions (arrowheads) and septate junctions (arrows) between an epidermal cell and an anchor cell and between an adhesive cell and an anchor cell. Note: microtubules (mt) within the adhesive gland. (E) Basal cytoplasmic extension of an anchor cell (ac) with intermediate filaments (if); the cell is connected to the extracellular matrix (ecm) via a hemidesmosome (hd). (F) Horizontal section through adhesive organs and an epidermal cell (ep) with cilia (ci) and microvilli (mv) protruding from the epidermal surface. Three adhesive organs are sectioned at different levels. Note that the anchor cell (ac) surrounds the adhesive gland (ag) and releasing gland (rg) cells in a donut-shaped manner, i.e. without cytoplasmic interruption. (G) Cross section through an adhesive organ with central adhesive gland (ag) and releasing gland (rg) cells surrounded by a collar of microvilli of the anchor cell (acmv). ac anchor cell; acmv anchor cell microvilli; ag adhesive gland; ci cilium; ecm extracellular matrix; ep epidermis; hd hemidesmosome; if intermediate filaments; mt microtubules; mv microvilli of regular epidermal cells; rg releasing gland; rh rhabdite glands, ultrarhabdites (urh). Scale bars (A) 5 μm, (C,F) 1 μm, (D,E,G) 0.5 μm.

Mentions: About 130 adhesive organs are present in adult M. lignano (see also [62]). Scanning electron microscopy revealed that each organ consists of an array of dense microvilli (Figure 2). A view onto the tip of the papillae showed the ring-like arrangement of the distal-most tips of the microvilli collar, which was closed above the tips of the adhesive and releasing glands (Figure 2D-G). Occasionally, small droplets of secreted material can be seen on the tip of an adhesive organ (Figure 2E). The microvilli were composed of bundles of actin filaments and were visualized with phalloidin staining and confocal (Figure 2H-J) and superresolution microscopy (STED) (Figure 2K, L). Lateral views on the papillae revealed labelling of individual microvilli (Figure 2K, L). In sagittal TEM sections of adhesive organs their internal organization became obvious. Each adhesive organ was comprised of three cell types, i.e. one adhesive gland cell - also referred to as the viscid gland cell [33], one releasing gland cell, and one anchor cell (Figure 3). The anchor cell is a modified epithelial cell with long microvilli that were closely attached next to each other forming a palisade-like envelope (Figure 3A, F, G) for the necks of the adhesive and releasing gland cells. The microvilli of the anchor cells protruded from the epidermis and surrounded the distal-most tips of both the adhesive- and releasing gland cells (Figure 3A-C, G). Within the microvilli collar of the anchor cell the adhesive gland cell was always located at the ventral side, and the releasing gland cell at the dorsal side, respectively (Figure 3A, B; see also Additional file 1). The anchor cell lacked cilia, ultrarhabdites (epitheliosomes), and a terminal web (Figure 3B). The cell body of the anchor cell lay in the parenchyma below the body wall musculature. The necks of the adhesive- and releasing gland cells penetrated the anchor cell and emerged through the anchor cell body forming - surrounded by the microvilli collar - the adhesive papillae on the body surface. The cell bodies of the adhesive gland cells (Additional file 2A) lay further anterior in the tail plate at the level of the stylet and the prostatic glands. The cell bodies of the releasing gland cells (Additional file 2B) were located posterior to the adhesive gland cell bodies, although there was a region of overlap (Figure 3A, Additional file 2C). In serial TEM sections of one specimen no cell bodies of releasing- or adhesive gland cells were present up to 16 μm from the tip of the tail. Between 17 to 23 μm from the tip of the tail only releasing gland cell bodies were found. In the region from 24 μm to 37 μm both, releasing- and adhesive gland cell bodies were present. From 37 μm onwards to 83 μm from the tip of the tail only adhesive gland cell bodies existed.


Biological adhesion of the flatworm Macrostomum lignano relies on a duo-gland system and is mediated by a cell type-specific intermediate filament protein.

Lengerer B, Pjeta R, Wunderer J, Rodrigues M, Arbore R, Schärer L, Berezikov E, Hess MW, Pfaller K, Egger B, Obwegeser S, Salvenmoser W, Ladurner P - Front. Zool. (2014)

Overview and fine structure of the M. lignano adhesive organs. Schematic illustration (A) and transmission electron microscopy (cryo-processed specimens) (B-G). (A) Localization of adhesive organ cell types: anchor cell (blue); adhesive gland (red); releasing gland (green). The red line indicates the level of the cross section of the adhesive papilla. (B) Sagittal section of the tip of the M. lignano tail plate. Four adhesive organs are visible and several gland cell necks reach into the tail plate. (C) Sagittal section of an adhesive organ. Inset: detail of respective vesicle types. (D) Section showing strengthened adherens junctions (arrowheads) and septate junctions (arrows) between an epidermal cell and an anchor cell and between an adhesive cell and an anchor cell. Note: microtubules (mt) within the adhesive gland. (E) Basal cytoplasmic extension of an anchor cell (ac) with intermediate filaments (if); the cell is connected to the extracellular matrix (ecm) via a hemidesmosome (hd). (F) Horizontal section through adhesive organs and an epidermal cell (ep) with cilia (ci) and microvilli (mv) protruding from the epidermal surface. Three adhesive organs are sectioned at different levels. Note that the anchor cell (ac) surrounds the adhesive gland (ag) and releasing gland (rg) cells in a donut-shaped manner, i.e. without cytoplasmic interruption. (G) Cross section through an adhesive organ with central adhesive gland (ag) and releasing gland (rg) cells surrounded by a collar of microvilli of the anchor cell (acmv). ac anchor cell; acmv anchor cell microvilli; ag adhesive gland; ci cilium; ecm extracellular matrix; ep epidermis; hd hemidesmosome; if intermediate filaments; mt microtubules; mv microvilli of regular epidermal cells; rg releasing gland; rh rhabdite glands, ultrarhabdites (urh). Scale bars (A) 5 μm, (C,F) 1 μm, (D,E,G) 0.5 μm.
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Figure 3: Overview and fine structure of the M. lignano adhesive organs. Schematic illustration (A) and transmission electron microscopy (cryo-processed specimens) (B-G). (A) Localization of adhesive organ cell types: anchor cell (blue); adhesive gland (red); releasing gland (green). The red line indicates the level of the cross section of the adhesive papilla. (B) Sagittal section of the tip of the M. lignano tail plate. Four adhesive organs are visible and several gland cell necks reach into the tail plate. (C) Sagittal section of an adhesive organ. Inset: detail of respective vesicle types. (D) Section showing strengthened adherens junctions (arrowheads) and septate junctions (arrows) between an epidermal cell and an anchor cell and between an adhesive cell and an anchor cell. Note: microtubules (mt) within the adhesive gland. (E) Basal cytoplasmic extension of an anchor cell (ac) with intermediate filaments (if); the cell is connected to the extracellular matrix (ecm) via a hemidesmosome (hd). (F) Horizontal section through adhesive organs and an epidermal cell (ep) with cilia (ci) and microvilli (mv) protruding from the epidermal surface. Three adhesive organs are sectioned at different levels. Note that the anchor cell (ac) surrounds the adhesive gland (ag) and releasing gland (rg) cells in a donut-shaped manner, i.e. without cytoplasmic interruption. (G) Cross section through an adhesive organ with central adhesive gland (ag) and releasing gland (rg) cells surrounded by a collar of microvilli of the anchor cell (acmv). ac anchor cell; acmv anchor cell microvilli; ag adhesive gland; ci cilium; ecm extracellular matrix; ep epidermis; hd hemidesmosome; if intermediate filaments; mt microtubules; mv microvilli of regular epidermal cells; rg releasing gland; rh rhabdite glands, ultrarhabdites (urh). Scale bars (A) 5 μm, (C,F) 1 μm, (D,E,G) 0.5 μm.
Mentions: About 130 adhesive organs are present in adult M. lignano (see also [62]). Scanning electron microscopy revealed that each organ consists of an array of dense microvilli (Figure 2). A view onto the tip of the papillae showed the ring-like arrangement of the distal-most tips of the microvilli collar, which was closed above the tips of the adhesive and releasing glands (Figure 2D-G). Occasionally, small droplets of secreted material can be seen on the tip of an adhesive organ (Figure 2E). The microvilli were composed of bundles of actin filaments and were visualized with phalloidin staining and confocal (Figure 2H-J) and superresolution microscopy (STED) (Figure 2K, L). Lateral views on the papillae revealed labelling of individual microvilli (Figure 2K, L). In sagittal TEM sections of adhesive organs their internal organization became obvious. Each adhesive organ was comprised of three cell types, i.e. one adhesive gland cell - also referred to as the viscid gland cell [33], one releasing gland cell, and one anchor cell (Figure 3). The anchor cell is a modified epithelial cell with long microvilli that were closely attached next to each other forming a palisade-like envelope (Figure 3A, F, G) for the necks of the adhesive and releasing gland cells. The microvilli of the anchor cells protruded from the epidermis and surrounded the distal-most tips of both the adhesive- and releasing gland cells (Figure 3A-C, G). Within the microvilli collar of the anchor cell the adhesive gland cell was always located at the ventral side, and the releasing gland cell at the dorsal side, respectively (Figure 3A, B; see also Additional file 1). The anchor cell lacked cilia, ultrarhabdites (epitheliosomes), and a terminal web (Figure 3B). The cell body of the anchor cell lay in the parenchyma below the body wall musculature. The necks of the adhesive- and releasing gland cells penetrated the anchor cell and emerged through the anchor cell body forming - surrounded by the microvilli collar - the adhesive papillae on the body surface. The cell bodies of the adhesive gland cells (Additional file 2A) lay further anterior in the tail plate at the level of the stylet and the prostatic glands. The cell bodies of the releasing gland cells (Additional file 2B) were located posterior to the adhesive gland cell bodies, although there was a region of overlap (Figure 3A, Additional file 2C). In serial TEM sections of one specimen no cell bodies of releasing- or adhesive gland cells were present up to 16 μm from the tip of the tail. Between 17 to 23 μm from the tip of the tail only releasing gland cell bodies were found. In the region from 24 μm to 37 μm both, releasing- and adhesive gland cell bodies were present. From 37 μm onwards to 83 μm from the tip of the tail only adhesive gland cell bodies existed.

Bottom Line: About 130 adhesive organs are located in a horse-shoe-shaped arc along the ventral side of the tail plate.RNA interference mediated knock-down resulted in the first experimentally induced non-adhesion phenotype in any marine animal.Therefore, our current findings and future investigations using this powerful flatworm model system might contribute to a better understanding of the function of intermediate filaments and their associated human diseases.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Zoology and Center of Molecular Bioscience Innsbruck, University of Innsbruck, Technikerstr, 25, Innsbruck A-6020, Austria. peter.ladurner@uibk.ac.at.

ABSTRACT

Background: Free-living flatworms, in both marine and freshwater environments, are able to adhere to and release from a substrate several times within a second. This reversible adhesion relies on adhesive organs comprised of three cell types: an adhesive gland cell, a releasing gland cell, and an anchor cell, which is a modified epidermal cell responsible for structural support. However, nothing is currently known about the molecules that are involved in this adhesion process.

Results: In this study we present the detailed morphology of the adhesive organs of the free-living marine flatworm Macrostomum lignano. About 130 adhesive organs are located in a horse-shoe-shaped arc along the ventral side of the tail plate. Each organ consists of exactly three cells, an adhesive gland cell, a releasing gland cell, and an anchor cell. The necks of the two gland cells penetrate the anchor cell through a common pore. Modified microvilli of the anchor cell form a collar surrounding the necks of the adhesive- and releasing glands, jointly forming the papilla, the outer visible part of the adhesive organs. Next, we identified an intermediate filament (IF) gene, macif1, which is expressed in the anchor cells. RNA interference mediated knock-down resulted in the first experimentally induced non-adhesion phenotype in any marine animal. Specifically, the absence of intermediate filaments in the anchor cells led to papillae with open tips, a reduction of the cytoskeleton network, a decline in hemidesmosomal connections, and to shortened microvilli containing less actin.

Conclusion: Our findings reveal an elaborate biological adhesion system in a free-living flatworm, which permits impressively rapid temporary adhesion-release performance in the marine environment. We demonstrate that the structural integrity of the supportive cell, the anchor cell, is essential for this adhesion process: the knock-down of the anchor cell-specific intermediate filament gene resulted in the inability of the animals to adhere. The RNAi mediated changes of the anchor cell morphology are comparable to situations observed in human gut epithelia. Therefore, our current findings and future investigations using this powerful flatworm model system might contribute to a better understanding of the function of intermediate filaments and their associated human diseases.

No MeSH data available.


Related in: MedlinePlus