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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

Domain organization (A) and primary structure (B) of the Macif1 protein. Hydrophobic residues are shown in black, hydrophilic residues in green, acidic residues in red and basic residues in blue. The characteristic heptad repeat pattern is shown as “abcdefg” and the apolar residues located at position “a” and “d” are indicated in yellow. The linker L2 that separates the coils 2A and 2B in vertebrate intermediate filaments is highlighted in grey. See text for more details.
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Figure 4: Domain organization (A) and primary structure (B) of the Macif1 protein. Hydrophobic residues are shown in black, hydrophilic residues in green, acidic residues in red and basic residues in blue. The characteristic heptad repeat pattern is shown as “abcdefg” and the apolar residues located at position “a” and “d” are indicated in yellow. The linker L2 that separates the coils 2A and 2B in vertebrate intermediate filaments is highlighted in grey. See text for more details.

Mentions: We have identified an intermediate filament gene macif1 (Figure 4) in an in situ hybridization screen [65] of a posterior-end specific transcriptome of M. lignano[66]. Details will be provided in future publications. Briefly, 200 animals were amputated posterior to the ovaries and 100 intact animals were used as control. For both samples 20 million Illumina reads (36 bp) were generated. The obtained reads were then mapped to the M. lignano transcriptome. In this way transcripts expressed in the posterior end were identified. From this dataset the expression of 48 genes was analysed and one was localized in the anchor cells of the adhesive organs. A BLAST search revealed an intermediate filament-like gene which we refer to as macif1. We cloned and sequenced macif1 and identified an open reading frame of 1815 bp encoding for 605 amino acids. The primary amino acid sequence of Macif1 contained all domains characteristic for a bona fide invertebrate intermediate filament protein including a head-, a rod- and a tail domain (Figure 4A). Within the central rod domains a distinct periodic heptamer signature (indicated as”abcdefg” in Figure 4B) with a characteristic [67] distribution of apolar residues at the positions “a” and “d” (indicated yellow in Figure 4B) was present. In the central part of the coil 2 subdomain the heptad repeats were interrupted by a discontinuity, the so called stutter (indicated by an arrow in Figure 4B). The Macif1 predicted protein shared the long version of the 1B subdomain with six additional heptamers (indicated with a blue double headed arrow in Figure 4B) present in all protostome intermediate filaments and in vertebrate lamins, but not in e.g. human vimentin and other vertebrate intermediate filament proteins (Figure 4B). Two regions across all intermediate filaments are particularly well conserved. These regions play a role in dimer-dimer formation [68] and were also present in the predicted Macif1 protein. They span the first part of coil 1A and the very end of coil 2B. In summary, the structural organization of Macif1 confirms its close relationship to other invertebrate intermediate filament proteins.


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)

Domain organization (A) and primary structure (B) of the Macif1 protein. Hydrophobic residues are shown in black, hydrophilic residues in green, acidic residues in red and basic residues in blue. The characteristic heptad repeat pattern is shown as “abcdefg” and the apolar residues located at position “a” and “d” are indicated in yellow. The linker L2 that separates the coils 2A and 2B in vertebrate intermediate filaments is highlighted in grey. See text for more details.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4016567&req=5

Figure 4: Domain organization (A) and primary structure (B) of the Macif1 protein. Hydrophobic residues are shown in black, hydrophilic residues in green, acidic residues in red and basic residues in blue. The characteristic heptad repeat pattern is shown as “abcdefg” and the apolar residues located at position “a” and “d” are indicated in yellow. The linker L2 that separates the coils 2A and 2B in vertebrate intermediate filaments is highlighted in grey. See text for more details.
Mentions: We have identified an intermediate filament gene macif1 (Figure 4) in an in situ hybridization screen [65] of a posterior-end specific transcriptome of M. lignano[66]. Details will be provided in future publications. Briefly, 200 animals were amputated posterior to the ovaries and 100 intact animals were used as control. For both samples 20 million Illumina reads (36 bp) were generated. The obtained reads were then mapped to the M. lignano transcriptome. In this way transcripts expressed in the posterior end were identified. From this dataset the expression of 48 genes was analysed and one was localized in the anchor cells of the adhesive organs. A BLAST search revealed an intermediate filament-like gene which we refer to as macif1. We cloned and sequenced macif1 and identified an open reading frame of 1815 bp encoding for 605 amino acids. The primary amino acid sequence of Macif1 contained all domains characteristic for a bona fide invertebrate intermediate filament protein including a head-, a rod- and a tail domain (Figure 4A). Within the central rod domains a distinct periodic heptamer signature (indicated as”abcdefg” in Figure 4B) with a characteristic [67] distribution of apolar residues at the positions “a” and “d” (indicated yellow in Figure 4B) was present. In the central part of the coil 2 subdomain the heptad repeats were interrupted by a discontinuity, the so called stutter (indicated by an arrow in Figure 4B). The Macif1 predicted protein shared the long version of the 1B subdomain with six additional heptamers (indicated with a blue double headed arrow in Figure 4B) present in all protostome intermediate filaments and in vertebrate lamins, but not in e.g. human vimentin and other vertebrate intermediate filament proteins (Figure 4B). Two regions across all intermediate filaments are particularly well conserved. These regions play a role in dimer-dimer formation [68] and were also present in the predicted Macif1 protein. They span the first part of coil 1A and the very end of coil 2B. In summary, the structural organization of Macif1 confirms its close relationship to other invertebrate intermediate filament proteins.

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