Bioadhesion meets functional genomics in flatworms

Bio-inspired adhesives have the potential establishing the basis for innovative industrial adhesives to be used in biomedicine or for high-tech applications. A broad range of organisms use adhesives to attach to substrates but the nature of these glues is not well understood. Current efforts are aiming to unravel the molecular basis of biological adhesion of diverse organisms. We are investigating free-living flatworms (Platyhelminthes) which are able to adhere and release from the substrate using duo-gland adhesive organs. Our model organism - the free-living flatworm Macrostomum lignano possesses about 130 adhesive organs, which enable the worm to adhere to and release rapidly from the substrate. The adhesive organs consist of three cell types, an adhesive gland cell, a releasing gland cell, and a modified epidermal cell. Based on our knowledge of the morphology and the available molecular biology tools we aim to characterize molecules involved in the adhesion and releasing process. Using comparative transcriptomics in combination with a large-scale in situ hybridization screen, we could so far identify 29 possible adhesion or releasing related transcripts. Further investigations may lead to the finding of a de novo bio-mimicked glue and a corresponding solvent.

Supported by FWF P25404-B25 and COST action TD090

Members of this workgroup are

• Peter Ladurner (head)
• Philip Bertemes
• Martin Dvorak
• Robert Pjeta

Gene regulatory switches

The control units of developmental episodes are transcription factors and their cis-regulatory elements capable of integrating developmental signals. They form evolutionary conserved building blocks for animal development and, when misregulated, are often involved in human disease including various forms of cancer.

Particularly interesting are transcription factors capable of switching between transcriptional activation and repression that allows binary cell fate choice upon cell division. Notably, repressive function could add regulative possibilities such as repression checkpoints or developmental pausing for diversification of cell fate.

We have observed switching behaviour for the three transcription factor families (ETS, GATA and TCF) crucially involved in early ectoderm patterning in ascidians.

The ascidian pluripotent ectoderm is particularly suitable to study transcriptional switching mechanisms in vivo as binary events for building precursor of mesendoderm vs. ectoderm, or epidermal vs. neural and/or neurosensorial cells is known with cellular resolution. Furthermore, the precicely spaced and timed activation of direct target genes of above transcription factors and knowledge of corresponding regulatory regions provides an entry point for deciphering the regulatory switching behaviour as activators or repressors.

We use the simplicity of Ciona intestinalis (genomic non-redundancy, fixed lineage and electroporation technique) to learn in depth about the funtions of these evolutionary conserved molecules in vivo, and especially about their less analysed, partially novel role as cell fate switches.

This topic is subject to a PhD thesis for Willi Kari (ÖAW, TWF and UIBK funding) and a master thesis for Johannes Will. The projects were partially begun in Patrick Lemaire 's lab at IBDM, Marseille, France (now CRBM, Montpellier), collaboration also with Mike Gilchrist, Crick Institute London, UK.

We collaborate with Vincent Bertrand , IBDM, France, and Yutaka Satou , Kyoto, Japan, on novel aspects of TCF function. Interactions within the UIBK Doctoral School AgeReg are planned on this topic with the Hobmayer, Edenhofer, Jansen-Dürr and Zwerschke labs.

Ascidian bioadhesion

Freeswimming ascidian larvae produce adhesives when settling at the beginning of metamorphosis to form sessile adults. Consequently, ascidians are major biofoulers threatening marine shipping and food industries.

To define their adhesive properties we describe the ascidian larval adhesive organs and integrate knowledge about its stepwise building from neurectoderm in molecular terms. We isolate candidate genes by transcriptomics, proteomics and functional genomics and test their role in adhesive organ formation and adhesive production. Our research may contribute to the design of both, industrial anti-fouling reagents and, medically relevant tissue compatible glues. We are members of the EU-COSTActionsTD0906 and CA15216 on Bioadhesion and in the EU Management Committee for Austria since 2017.

This topic is subject to a PhD thesis for Fan Zeng (UIBK and ÖAW funding, UIBK Doctoral School AgeReg).

Collaboration with Peter Ladurner, UIBK : co-supervision of PhD student Julia Wunderer (funding Südtiroler Stipendium, TWF, UIBK), MASS-Spec and NGS (Markus Lindner, MUI and ETH Zürich) and Willi Salvenmoser , UIBK. Further collaborations with Daniel Sobral , Gulbenkian Institute, Portugal (differential transcriptomics) and Roberta Pennati , University Milan, Italy. Additional funding: EU-COST ActionsTD0906 and CA15216 Biological adhesives. A COST action Training school was held by us at UIBK in September 2017.

Members of this workgroup are

• Ute Rothbächer (head)

Animal body plan evolution

Canonical Wnt and Bmp/Chordin signalling in axis formation and regenerat

Cnidarians exhibit a highly conserved canonical Wnt pathway. In the hydrozoan polyp Hydra, this pathway represents a key element in the head organizer, which controls positional information along the major oral-aboral body axis and during regeneration. In the anthozoan polyp Nematostella, Wnts are activated at the blastoporal organizer during gastrulation, which later develops into the head of the polyps. In both species, we can induce ectopic head structures or inhibit head formation by using small molecule inhibitors against GSK3 and beta-Catenin, respectively. In the loerm, our studies aim at a more complete understanding of the molecular network acting in these organizers. Our previous results also suggested that the Bmp/Chordin signalling system acts in patterning the cnidarian oral-aboral axis with Chordin being activated in the oral organizers. In bilaterians, this signalling system regulates dorsal-ventral axis formation. In order to trace the origin of the bilaterian body axes from more radially symmetric ancestors, we have started to study Wnt and Bmp/Chordin pathways in the basal bilaterian flatworms Macrostomum lignano (Rhabditophora) and Isodiametra pulchra (Acoelomorpha).

Non-canonical Wnt signalling and actin dynamics during tissue evagination

Basal eumetazoans were the first animals to invent complex morphogenetic tissue movements resulting in body outgrowths and appendages. To approach the molecular basis of tissue evagination in Hydra, a basal eumetazoan, we characterized a noncanonical Wnt signalling pathway including Wnt5, Wnt8, Frizzled2, JNK, Rho-kinase, and Strabismus. This pathway acts in convergent extension-like tissue movements during bud and tentacle evagination. Interestingly, non-canonical Wnt signalling is directly activated by the canonical Wnt pathway in Hydra. This coordination seems to be essential to define the correct polyp body plan with tentacles and buds evaginating at the appropriate positions along the oral-aboral body axis. In the future, we aim at a more detailed analysis of the molecular interaction between canonical and non-canonical Wnt signalling in cnidarians. Furthermore, we plan to characterize those actin-binding proteins involved in cell polarization during bud and tentacle formation in order to gain more insight in the mechanics of tissue evagination.

Cadherin-catenin based cell adhesion and the establishment of true epithelia

Evolution of true epithelia was a major invention in eumetazoan phylogeny (Hyman: "animals of tissue grade"). Epithelial cells exhibit apical-basal polarity, apical cell-cell junctions, and cell contact sites to a basal extracellular matrix. Hydra is an excellent experimental system to approach the evolution of cell adhesion and epithelial tissues, because it offers access to complete self-organization in reaggregation assays starting from single cell suspensions. In the recent past, we have characterized the core members of a Cadherin-Catenin cell adhesion complex in Hydra. We also identified desmosomal junctions in epithelial cells in Hydra. All these data support the view that cnidarians have a functional classic Cadherin-Catenin adhesion complex that is involved in the establishment of cell-cell contact sites. Currently, we aim at the precise intracellular localization of these proteins by using immunogold-stainings in transmission electron microscopy. As a long term perspective, we want to understand how cell adhesion and inductive signalling cooperate during self-organization.

Members of this workgroup are

Bert Hobmayer (head)

Regeneration

Wir interessieren uns für das Regenerationsvermögen von freilebenden Plattwürmern und studieren Regenerationsprozesse in einem Plattwurm-Modellorganismus namens Macrostomum lignano. M. lignano und andere Plattwürmer, u.a. Polycladen, sind für unsere Arbeit besonders gut geeignet aufgrund ihrer beachtlichen Regenerationsleistung und ihrem wahrscheinlich totipotenten, also allmächtigen, Stammzellsystem.

Das Sichtbarmachen von Stammzellen mit BrdU (Bromodeoxyuridin) in ganzen Tieren von Macrostomum lignano und in histologischen Schnitten gibt Hinweise auf Antworten zu folgenden Fragen:

Welche Eigenschaften hat ein Regenerationsblastem?
Wie reagiert das Stammzellsystem auf die Amputation eines Körperteils?
Wieviele Stammzellen sind für eine erfolgreiche Regeneration nötig?

Wir versuchen zudem, das Verhältnis und die Ähnlichkeiten zwischen Regenerationsprozessen und der embryonalen und postembryonalen Entwicklung zu verstehen.Von großer Tragweite ist die Frage, ob wiederholte Amputation und Regeneration eines einzelnen Plattwurms Alterungsprozesse verlangsamen oder sogar umkehren kann.

Mitarbeiter dieser Arbeitsgruppe

• Bernhard Egger (head)
• Isabel Dittmann (PhD student)
• Moses Kibet (PhD student)
• Simon Köll (master student)
• Clemens Gotsis (master student)
• Davina Düngler (master student)

Stammzellen 

Stammzellen sind undifferenzierte Zellen mit der Fähigkeit zur Selbsterneuerung und der Bildung von differenzierten Tochterzellen. Stammzellen sind von den meisten Organismen und dem Menschen bekannt. Sie sind als pluripotente Zellpopulationen vorhanden, d.h. sie haben eine limitiertes Differenzierungspotential. Plathelminten jedoch besitzen ein totipotentes Stammzellsystem, d.h. diese Stammzellen - in diesen Tiere auch Neoblasten genannt - können in sämtliche Zelltypen differenzieren, einschließlich der Keimbahnzellen. Neoblasten sind während der gesamten Entwicklung aktiv, sorgen für permanente Zellerneuerung in Adulttieren und bilden die Grundlage der außergewöhnlichen Regenerationsfähigkeit von Platyhelminthen. Erstaunlicherweise sind die Gene die Stammzellerneuerung, Regeneration und Keimbahnspezifizierung steuern hoch konserviert und bei anderen Modellorganismen und sogar bis hin zu Pflanzen homolog. Unsere Arbeitsgruppe untersucht das Stammzellsystem der basalen Plathelminten Macrostomum lignano und dem acoelen Isodiametra pulchra mit immuncytochemischen, histologischen, ultrastrukturellen und molekularen Methoden. Die besonderen Eigenschaften des Stammzellsystems von Plathelminten, der einfache experimentelle Zugang, die einfache Haltung der Tiere ermöglichen die Untersuchung von grundlegenden Mechanismen von Stammzellerhaltung und -differenzierung. Die beteiligten hoch konservierten Gene erlauben Rückschlüsse auf Stammzellsysteme bei anderen Tieren und beim Menschen. 

Mitarbeiter dieser Arbeitsgruppe

• Peter Ladurner (Leiter)