@article {153, title = {Different roads to form the same gut in nematodes}, journal = {Evolution \& DevelopmentEvolution \& Development}, volume = {8}, number = {4}, year = {2006}, note = {Times Cited: 1 Article English Borgonie, G Univ Ghent, Dept Biol, KL Ledeganckstr 35, B-9000 Ghent, Belgium Cited References Count: 40 058HC BLACKWELL PUBLISHING 9600 GARSINGTON RD, OXFORD OX4 2DQ, OXON, ENGLAND OXFORD}, pages = {362-369}, abstract = {The morphogenesis of a gut from the endoderm has been well studied among the animal kingdom and is also well described in the nematode Caenorhabditis elegans. But are there other ways to build a nematode intestine? Sulston et al. (1983) described a different intestinal cell lineage in the species Panagrellus redivivus and Turbatrix aceti that includes two programmed cell deaths. However, no details are known about the three-dimensional (3D) configuration and the role of the cell deaths. Here, we describe the intestinal morphogenesis of P. redivivus and five other nematode species by means of four-dimensional microscopy, which gives us a 3D representation of gut formation at the cellular level. The morphological pathway of gut formation is highly conserved among these distantly related species. However, we found the P. redivivus pattern in another related species Halicephalobus gingivalis. In this pattern, the intestinal precursors migrate inward in concert with the mesoderm precursors. Based on the observations, we propose a hypothesis that could explain the differences. The positions of the mesoderm precursors create a possible spatial constraint, by which the establishment of bilateral symmetry in the intestine is delayed. This symmetry is corrected by cell migrations; other cells are eliminated and compensated by supplementary cell divisions. This pattern leads to the same result as in the other nematodes: a bilateral symmetrical intestine with nine rings. This illustrates how conserved body plans can be achieved by different developmental mechanisms}, keywords = {C-ELEGANS, Caenorhabditis, Caenorhabditis elegans, caenorhabditis-elegans, CELLS, EMBRYOGENESIS, EMBRYONIC-CELL LINEAGE, Evolution, FATE, INDUCTION, microscopy, MODEL, NEMATODE, nematodes, SPECIFICATION}, isbn = {1520-541X}, author = {Houthoofd, W. and Willems, M. and Vangestel, S. and Mertens, C. and Bert, W. and Borgonie, G.} } @article {163, title = {Unusual intestinal lamellae in the nematode Rhabditophanes sp KR3021 (Nematoda : Alloinematidae)}, journal = {Journal of MorphologyJournal of Morphology}, volume = {264}, number = {2}, year = {2005}, note = {Willems, M Houthoofd, W Claeys, M Couvreur, M Van Driessche, R Adriaens, D Jacobsen, K Borgonie, G}, month = {May}, pages = {223-232}, abstract = {The free-living nematode Rhabditophanes sp. has recently been placed in a clade of animal parasites and may be a unique example of a reversal to a nonparasitic lifestyle. Detailed morphological analysis of the intestine reveals the unusual and unique structure of splitting microlamellae forming a meshwork with cavities along the entire intestinal tract. Secretion vesicles were observed along the whole tract and along the length of the lamellae. It is suggested that these lamellae are adaptations to a different digestive strategy where low food availability and a low absorption surface are compensated for by maximizing the nutrient uptake efficiency along the entire length of the intestine. The likely reversal to a free-living life cycle may have caused drastic changes in diet, providing the necessary driving forces to such morphological changes. (c) 2005 Wiley-Liss, Inc.}, isbn = {0362-2525}, author = {Willems, M. and Houthoofd, W. and Claeys, M. and Couvreur, M. and Van Driessche, R. and Adriaens, D. and Jacobsen, K. and Borgonie, G.} } @article {109, title = {Use of freeze-cracking in ontogenetic research in Macrostomum lignano (Macrostomida, Rhabditophora)}, journal = {Development Genes and EvolutionDevelopment Genes and Evolution}, volume = {219}, number = {5}, year = {2009}, note = {Willems, Maxime Boone, Mieke Couvreur, Marjolein De Mulder, Katrien Van Ranst, Jelka Artois, Tom Borgonie, Gaetan}, month = {May}, pages = {273-279}, abstract = {A method for studying whole mount flatworm embryos based on freeze-cracking of the eggs is described. This method allows successful immunohistological and immunocytological studies of whole mount embryos. It does not require the use of sharpened needles or a microinjection system to puncture the eggshell. Moreover, this method is more practical and less time-consuming than classical puncturing and much cheaper than the use of a microinjection system. The advantages of this method are illustrated by results of several immunolocalisation experiments in the macrostomid flatworm Macrostomum lignano. The optimal procedure and crucial steps for this method are discussed.}, isbn = {0949-944X}, author = {Willems, M. and Boone, M. and Couvreur, M. and De Mulder, K. and Van Ranst, J. and Artois, T. and Borgonie, G.} } @article {115, title = {The free-living flatworm Macrostomum lignano: A new model organism for ageing research}, journal = {Experimental GerontologyExperimental Gerontology}, volume = {44}, number = {4}, year = {2009}, note = {Mouton, Stijn Willems, Maxime Braeckman, Bart P. Egger, Bernhard Ladurner, Peter Schaerer, Lukas Borgonie, Gaetan}, month = {Apr}, pages = {243-249}, abstract = {To study the several elements and causes of ageing, diverse model organisms and methodologies are required. The most frequently used models are Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster and rodents. All have their advantages and disadvantages and allow studying particular aspects of the ageing process. During the last few years, several ageing studies focussed on stem cells and their role in tissue homeostasis. Here we present a new model organism which can study this relation where other model systems fail. The flatworm Macrostomum lignano possesses a dynamic population of likely totipotent somatic stem cells known as neoblasts. Several characteristics qualify M. lignano as a suitable model system for ageing studies in general and more specifically for gaining more insight in the causal relation between stem cells, ageing and rejuvenation. In this review, we will briefly describe the species and its life history, and discuss the role of its stem cells in ageing and rejuvenation. We also give an overview of the available experimental tools that allow a multidisciplinary approach for studying ageing in M. lignano. (C) 2008 Elsevier Inc. All rights reserved.}, isbn = {0531-5565}, author = {Mouton, S. and Willems, M. and Braeckman, B. P. and Egger, B. and Ladurner, P. and Scharer, L. and Borgonie, G.} } @article {116, title = {Demographic analysis reveals gradual senescence in the flatworm Macrostomum lignano}, journal = {Frontiers in ZoologyFrontiers in Zoology}, volume = {6}, year = {2009}, note = {Mouton, Stijn Willems, Maxime Back, Patricia Braeckman, Bart P. Borgonie, Gaetan}, month = {Jul}, abstract = {Free-living flatworms ("Turbellaria") are appropriate model organisms to gain better insight into the role of stem cells in ageing and rejuvenation. Ageing research in flatworms is, however, still scarce. This is partly due to culture difficulties and the lack of a complete set of demographic data, including parameters such as median lifespan and age-specific mortality rate. In this paper, we report on the first flatworm survival analysis. We used the species Macrostomum lignano, which is an emerging model for studying the reciprocal influence between stem cells, ageing and rejuvenation. This species has a median lifespan of 205 +/- 13 days (average +/- standard deviation [SD]) and a 90(th) percentile lifespan of 373 +/- 32 days. The maximum lifespan, however, is more than 745 days, and the average survival curve is characterised by a long tail because a small number of individuals lives twice as long as 90\% of the population. Similar to earlier observations in a wide range of animals, in M. lignano the age-specific mortality rate increases exponentially, but levels off at the oldest ages. To compare the senescence of M. lignano with that of other ageing models, we determined the mortality rate doubling time, which is 0.20 +/- 0.02 years. As a result, we can conclude that M. lignano shows gradual senescence at a rate similar to the vertebrate ageing models Rattus norvegicus and Mus musculus. We argue that M. lignano is a suitable model for ageing and rejuvenation research, and especially for the role of stem cells in these processes, due to its accessible stem cell system and regeneration capacity, and the possibility of combining stem cell studies with demographic analyses.}, isbn = {1742-9994}, author = {Mouton, S. and Willems, M. and Back, P. and Braeckman, B. P. and Borgonie, G.} } @article {125, title = {Stem cells are differentially regulated during development, regeneration and homeostasis in flatworms}, journal = {Developmental BiologyDevelopmental Biology}, volume = {334}, number = {1}, year = {2009}, note = {De Mulder, Katrien Pfister, Daniela Kuales, Georg Egger, Bernhard Salvenmoser, Willi Willems, Maxime Steger, Jessica Fauster, Katja Micura, Ronald Borgonie, Gaetan Ladurner, Peter}, month = {Oct}, pages = {198-212}, abstract = {The flatworm stem cell system is exceptional within the animal kingdom, as totipotent stem cells (neoblasts) are the only dividing cells within the organism. In contrast to most organisms, piwi-like gene expression in. flatworms is extended from germ cells to somatic stem cells. We describe the isolation and characterization of the piwi homologue macpiwi in the flatworm Macrostomum lignano. We use in situ hybridization, antibody staining and RNA interference to study macpiwi expression and function in adults, during postembryonic development, regeneration and upon starvation. We found novelties regarding piwi function and observed differences to current piwi functions in flatworms. First, macpiwi was essential for the maintenance of somatic stem cells in adult animals. A knock-down of macpiwi led to a complete elimination of stem cells and death of the animals. Second, the regulation of stem cells was different in adults and regenerates compared to postembryonic development. Third, sexual reproduction of M. lignano allowed to follow germline formation during postembryonic development, regeneration, and starvation. Fourth, piwi expression in hatchlings further supports an embryonic formation of the germline in M. lignano. Our findings address new questions in flatworm stem cell research and provide a basis for comparison with higher organisms. (C) 2009 Elsevier Inc. All rights reserved.}, isbn = {0012-1606}, author = {De Mulder, K. and Pfister, D. and Kuales, G. and Egger, B. and Salvenmoser, W. and Willems, M. and Steger, J. and Fauster, K. and Micura, R. and Borgonie, G. and Ladurner, P.} } @article {126, title = {Characterization of the stem cell system of the acoel Isodiametra pulchra}, journal = {Bmc Developmental BiologyBmc Developmental Biology}, volume = {9}, year = {2009}, note = {De Mulder, Katrien Kuales, Georg Pfister, Daniela Willems, Maxime Egger, Bernhard Salvenmoser, Willi Thaler, Marlene Gorny, Anne-Kathrin Hrouda, Martina Borgonie, Gaetan Ladurner, Peter}, month = {Dec}, abstract = {Background: Tissue plasticity and a substantial regeneration capacity based on stem cells are the hallmark of several invertebrate groups such as sponges, cnidarians and Platyhelminthes. Traditionally, Acoela were seen as an early branching clade within the Platyhelminthes, but became recently positioned at the base of the Bilateria. However, little is known on how the stem cell system in this new phylum is organized. In this study, we wanted to examine if Acoela possess a neoblast-like stem cell system that is responsible for development, growth, homeostasis and regeneration. Results: We established enduring laboratory cultures of the acoel Isodiametra pulchra (Acoela, Acoelomorpha) and implemented in situ hybridization and RNA interference (RNAi) for this species. We used BrdU labelling, morphology, ultrastructure and molecular tools to illuminate the morphology, distribution and plasticity of acoel stem cells under different developmental conditions. We demonstrate that neoblasts are the only proliferating cells which are solely mesodermally located within the organism. By means of in situ hybridisation and protein localisation we could demonstrate that the piwi-like gene ipiwi1 is expressed in testes, ovaries as well as in a subpopulation of somatic stem cells. In addition, we show that germ cell progenitors are present in freshly hatched worms, suggesting an embryonic formation of the germline. We identified a potent stem cell system that is responsible for development, homeostasis, regeneration and regrowth upon starvation. Conclusions: We introduce the acoel Isodiametra pulchra as potential new model organism, suitable to address developmental questions in this understudied phylum. We show that neoblasts in I. pulchra are crucial for tissue homeostasis, development and regeneration. Notably, epidermal cells were found to be renewed exclusively from parenchymally located stem cells, a situation known only from rhabditophoran flatworms so far. For further comparison, it will be important to analyse the stem cell systems of other key-positioned understudied taxa.}, isbn = {1471-213X}, author = {De Mulder, K. and Kuales, G. and Pfister, D. and Willems, M. and Egger, B. and Salvenmoser, W. and Thaler, M. and Gorny, A. K. and Hrouda, M. and Borgonie, G. and Ladurner, P.} } @article {132, title = {Assessment of the configuration of the posterior cells of the nematode embryo as potential phylogenetic marker}, journal = {Russian Journal of NematologyRussian Journal of Nematology}, volume = {16}, number = {2}, year = {2008}, note = {Times Cited: 0 Article English Vangestel, S Univ Ghent, Dept Biol, Nematol Sect, KL Ledeganckstr 35, B-9000 Ghent, Belgium Cited References Count: 55 383BP MYLNEFIELD RESEARCH SERVICES INVERGOWRIE, DUNDEE DD2 5DA, SCOTLAND DUNDEE}, pages = {107-120}, abstract = {We have reconstructed the evolutionary history of an early developmental character by mapping the configuration of the posterior cells in the early embryo onto the SSU-based molecular phylogeny of Holterman (2006). We have analyzed the early embryonic development of 19 species, complemented with 20 species from the literature, covering representatives in each clade. We show that the Caenorhabditis elegans configuration, found in most species in clade III-X, is the ancestral state for these clades. alternative configurations arose inependently in clade IX, (Diploscapter coronatus), X (Halicephalobus gingivalis), XI (all investigated species) and XII (Meloidogyne incognita). A variable configuration of the posterior cells arose at least twice independently during nematode evolution, once in clade IX (D. coronatus) and once in an ancestor, shared by clade XI and XII and thus can be used as a phylogenetic marker to delineate these clades. Statistical tests based on our data-set show that the presence of a variable configuration is related to developmental tempo and egg shape}, keywords = {Belgium, C-ELEGANS EMBRYOS, Caenorhabditis, Caenorhabditis elegans, caenorhabditis-elegans, CELLS, CLEAVAGE, EARLY EMBRYOGENESIS, embryology, ENOPLIDA, Evolution, GUT, LINEAGE, MELOIDOGYNE, MOLECULAR PHYLOGENY, Nematoda, NEMATODE, phylogenetic marker, PHYLOGENIES, phylogeny, spatial configuration, SPECIFICATION}, isbn = {0869-6918}, author = {Vangestel, S. and Houthoofd, W. and Bert, W. and Vanholme, B. and Calderon-Urrea, A. and Willems, M. and Artois, T. and Borgonie, G.} } @article {136, title = {The embryonic cell lineage of the nematode Rhabditophanes sp}, journal = {International Journal of Developmental BiologyInternational Journal of Developmental Biology}, volume = {52}, number = {7}, year = {2008}, note = {Houthoofd, Wouter Willems, Maxime Jacobsen, Kim Coomans, August Borgonie, Gaetan}, pages = {963-967}, abstract = {One of the unique features of the model organism Caenorhabditis elegans is its invariant development, where a stereotyped cell lineage generates a fixed number of cells with a fixed cell type. It remains unclear how embryonic development evolved within the nematodes to give rise to the complex, invariant cell lineage of C. elegans. Therefore, we determined the embryonic cell lineage of the nematode, Rhabditophanes sp. (family Alloionematidae) and made detailed cell-by-cell comparison with the known cell lineages of C. elegans, Pellioditis marina and Halicephalobus gingivalis. This gave us a unique data set of four embryonic cell lineages, which allowed a detailed comparison between these cell lineages at the level of each individual cell. This lineage comparison revealed a similar complex polyclonal fate distribution in all four nematode species (85\% of the cells have the same fate). It is striking that there is a conservation of a {\textquoteright}C. elegans{\textquoteright} like polyclonal cell lineage with strong left-right asymmetry. We propose that an early symmetry-breaking event in nematodes of clade IV-V is a major developmental constraint which shapes their asymmetric cell lineage.}, isbn = {0214-6282}, author = {Houthoofd, W. and Willems, M. and Jacobsen, K. and Coomans, A. and Borgonie, G.} } @article {79, title = {Lack of metabolic ageing in the long-lived flatworm Schmidtea polychroa}, journal = {Experimental GerontologyExperimental Gerontology}, volume = {46}, number = {9}, year = {2011}, note = {Mouton, Stijn Willems, Maxime Houthoofd, Wouter Bert, Wim Braeckman, Bart P.}, month = {Sep}, pages = {755-761}, abstract = {Freshwater planarians have a large totipotent stem cell population allowing high rates of cell renewal and morphological plasticity. It is often suggested that they are able to rejuvenate during fission, regeneration and starvation. These features, together with the rapidly expanding molecular toolset, make planarians such as Schmidtea polychroa and S. mediterranea interesting for ageing research. Yet, the basic demographic and physiological data are lacking or still based on fragmentary observations of one century ago. Here, we present the first longitudinal physiological study of the species S. polychroa. Survival, size and metabolic rate, measured by microcalorimetry, of a cohort of 28 individuals were followed over a period of three years. Sexual maturity was reached during the second month after which the worms continued growing up to 5 months. This initial growth phase was followed by alternating periods of synchronised growth and degrowth. Although mass-specific metabolic rates declined during the initial growth phase, no changes were found later in life. The absence of metabolic ageing may be explained by the very high rate of cell renewal during homeostasis and alternating phases of degrowth and growth during which tissues are renewed. Surprisingly, all deaths occurred in pairs of worms that were housed in the same culture recipient, suggesting that worms did not die from ageing. Taking into account the metabolic and demographic data, we suggest that S. polychroa shows negligible ageing. Detailed analyses of size and metabolic rate revealed a remarkable biphasic allometric scaling relation. During the initial growth phase (months 1-5) the allometric scaling exponent b was 0.86 while later in life, it increased to an unusually large value of 1.17, indicating that mass-specific metabolic rate increases with size in adult S. polychroa. (C) 2011 Elsevier Inc. All rights reserved.}, isbn = {0531-5565}, author = {Mouton, S. and Willems, M. and Houthoofd, W. and Bert, W. and Braeckman, B. P.} } @article {86, title = {Distribution of proliferating cells and vasa-positive cells in the embryo of Macrostomum lignano (Rhabditophora, Platyhelminthes)}, journal = {Belgian Journal of ZoologyBelgian Journal of Zoology}, volume = {140}, year = {2010}, note = {Willems, Maxime Couvreur, Marjolein Boone, Mieke Houthoofd, Wouter Artois, Tom11th International Symposium on Flatworm BiologyJul 26-31, 2009Diepenbeek, BELGIUMS}, month = {Jul}, pages = {149-153}, abstract = {The neoblast stem cell system of flatworms is considered to be unique within the animal kingdom. How this stem cell system arises during embryonic development is intriguing. Therefore we performed bromodeoxyuridine labelling on late stage embryos of Macrostomum lignano to assess when the pattern of proliferating cells within the embryo is comparable to that of hatchlings. This pattern can be found in late embryonic stages ( stage 8). We also used the freeze cracking method to perform macvasa embryonic labelling. Macvasa is a somatic and germ line stem cell marker. We showed macvasa protein distribution during the whole embryonic development. In the macvasa-positive blastomeres the protein is localized around the nucleus in the putative chromatoid bodies. However, at a specific embryonic stage, it is also ubiquitously present in the cytoplasm of some blastomeres. We compare our data with what is known from Schmidtea polychroa of the expression of the vasa-like gene SpolvlgA and the protein distribution of the chromatoid body component Spoltud-1. The embryonic origin of the somatic stem cell system and the germ line is discussed.}, isbn = {0777-6276}, author = {Willems, M. and Couvreur, M. and Boone, M. and Houthoofd, W. and Artois, T.} } @article {93, title = {Establishing a flatworm ageing model}, journal = {Belgian Journal of ZoologyBelgian Journal of Zoology}, volume = {140}, year = {2010}, note = {Mouton, Stijn Verdoodt, Freija Willems, Maxime Dhondt, Ineke Crucke, Jeroen Braeckman, Bart P. Houthoofd, WouterS}, month = {Jul}, pages = {195-197}, isbn = {0777-6276}, author = {Mouton, S. and Verdoodt, F. and Willems, M. and Dhondt, I. and Crucke, J. and Braeckman, B. P. and Houthoofd, W.} } @article {102, title = {Refuge From Predation, the Benefit of Living in an Extreme Acidic Environment?}, journal = {Biological BulletinBiological Bulletin}, volume = {219}, number = {3}, year = {2010}, note = {Borgonie, Gaetan Dierick, Manuel Houthoofd, Wouter Willems, Maxime Jacobs, Patric Bert, Wim}, month = {Dec}, pages = {268-276}, abstract = {Organisms living in extreme habitats require costly adaptations to cope with these conditions. Among the suggested potential benefits that trade off these costs is refuge from predation. To study these interactions in extreme environments, samples were taken in the cave Cueva de Villa Luz, Tabasco, Mexico, where more than 32 subterranean springs, some H,S rich, rise from the floor. Hydrogen sulfide gas plus oxygen is absorbed by freshwater, and oxidation forms concentrated sulfuric acid. Snottites, whitish hollow mucous tubes, hang from the ceiling of the cave. Fluid drops from these snottites were recorded as having pH values of 0-3. We report the discovery of a new species of nematode that thrives in the highly acidic environment of the snottite. Micro CT scan of snottites reveals a complex interaction between the acidic snottite, nematodes, and abundant nematode-eating mites. The nematode adaptation to low pH probably protects them against mite predation, for which nematodes are most likely the most important source of carbon in this sulfur-driven ecosystem.}, isbn = {0006-3185}, author = {Borgonie, G. and Dierick, M. and Houthoofd, W. and Willems, M. and Jacobs, P. and Bert, W.} } @article {107, title = {Ontogeny of the Complex Sperm in the Macrostomid Flatworm Macrostomum lignano (Macrostomorpha, Rhabditophora)}, journal = {Journal of MorphologyJournal of Morphology}, volume = {270}, number = {2}, year = {2009}, note = {Willems, Maxime Leroux, Frederic Claeys, Myriam Boone, Mieke Mouton, Stijn Artois, Tom Borgonie, Gaetan}, month = {Feb}, pages = {162-174}, abstract = {Spermiogenesis in Macrostomum lignano (Macrostomorpha, Rhabditophora) is described using light- and electron microscopy of the successive stages in sperm development. Ovoid spermatids develop to highly complex, elongated sperm possessing an undulating distal (anterior) process (or "feeler"), bristles, and a proximal (posterior) brush. In particular, we present a detailed account of the morphology and ontogeny of the bristles, describing for the first time the formation of a highly specialized bristle complex consisting of several parts. This complex is ultimately reduced when sperm are mature. The implications of the development of this bristle complex on both sperm maturation and the evolution and function of the bristles are discussed. The assumed homology between bristles and flagellae questioned. J. Morphol. 270:162-174, 2009. (C) 2008 Wiley-Liss, Inc.}, isbn = {0362-2525}, author = {Willems, M. and Leroux, F. and Claeys, M. and Boone, M. and Mouton, S. and Artois, T. and Borgonie, G.} } @article {108, title = {Embryonic origins of hull cells in the flatworm Macrostomum lignano through cell lineage analysis: developmental and phylogenetic implications}, journal = {Development Genes and EvolutionDevelopment Genes and Evolution}, volume = {219}, number = {8}, year = {2009}, note = {Willems, Maxime Egger, Bernhard Wolff, Carsten Mouton, Stijn Houthoofd, Wouter Fonderie, Pamela Couvreur, Marjolein Artois, Tom Borgonie, Gaetan}, month = {Aug}, pages = {409-417}, abstract = {The development of macrostomid flatworms is of interest for evolutionary developmental biology research because these taxa combine characteristics of the canonical spiral cleavage pattern with significant deviations from this pattern. One such deviation is the formation of hull cells, which surround the remaining embryonic primordium during early development. Using live observations with a 4D microscope system, histology, and 3D reconstructions, we analyzed the ontogeny of these hull cells in the macrostomid model organism Macrostomum lignano. Our cell lineage analysis allowed us to find the precursors of the hull cells in this species. We discuss the relation between macrostomid development and the development of other spiralians and the question of whether hull cells are homologous within rhabditophoran flatworms.}, isbn = {0949-944X}, author = {Willems, M. and Egger, B. and Wolff, C. and Mouton, S. and Houthoofd, W. and Fonderie, P. and Couvreur, M. and Artois, T. and Borgonie, G.} } @article {56, title = {Stem cells propagate their DNA by random segregation in the flatworm Macrostomum lignano.}, journal = {PLoS ONEPLoS ONE}, volume = {7:e30227}, year = {2012}, author = {Verdoodt, F. and Willems, M. and Mouton, S. and De Mulder, K. and Bert, W., and Houthoofd, W. and Smith, J. and Ladurner, P.} } @article {57, title = {Measuring S-phase duration of adult stem cells in the flatworm Macrostomum lignano by double replication labelling and quantitative colocalization analysis}, journal = {Cell Biology InternationalCell Biology International}, volume = {doi:10.1042/CBI20120187}, year = {2012}, author = {Verdoodt, F. and Willems, M. and Dhondt, I. and Houthoofd, W. and Bert, W. and De Vos, W.H.} } @article {58, title = {Proliferative response of the stem cell system during regeneration of the rostrum in Macrostomum lignano (Platyhelminthes)}, journal = {Cell and Tissue ResearchCell and Tissue Research}, volume = {347}, year = {2012}, pages = {397{\textendash}406}, author = {Verdoodt, F. and Bert, W. and Couvreur, M. and Willems, M.} }