01834nas a2200217   4500008004100000020001400041245009100055210006900146260000800215300001200223490000700235520121100242100001501453700001601468700002201484700001401506700001701520700001601537700001701553856004601570       2009                        eng d  a0531-556500aThe free-living flatworm Macrostomum lignano: A new model organism for ageing research0 afreeliving flatworm Macrostomum lignano A new model organism for  cApr  a243-2490 v443 aTo 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.1 aMouton, S.1 aWillems, M.1 aBraeckman, B., P.1 aEgger, B.1 aLadurner, P.1 aScharer, L.1 aBorgonie, G.  uhttps://nematodes.myspecies.info/node/11502162nas a2200265   4500008004100000020001400041245010600055210006900161260000800230300001200238490000800250520141300258100001801671700001601689700001501705700001401720700002001734700001601754700001501770700001601785700001501801700001701816700001701833856004601850       2009                        eng d  a0012-160600aStem cells are differentially regulated during development, regeneration and homeostasis in flatworms0 aStem cells are differentially regulated during development regen  cOct  a198-2120 v3343 aThe 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.1 aDe Mulder, K.1 aPfister, D.1 aKuales, G.1 aEgger, B.1 aSalvenmoser, W.1 aWillems, M.1 aSteger, J.1 aFauster, K.1 aMicura, R.1 aBorgonie, G.1 aLadurner, P.  uhttps://nematodes.myspecies.info/node/12502812nas a2200253   4500008004100000020001400041245008500055210006900140260000800209490000600217520210800223100001802331700001502349700001602364700001602380700001402396700002002410700001502430700001802445700001502463700001702478700001702495856004602512       2009                        eng d  a1471-213X00aCharacterization of the stem cell system of the acoel <i>Isodiametra pulchra</i>0 aCharacterization of the stem cell system of the acoel iIsodiamet  cDec0 v93 aBackground: 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.1 aDe Mulder, K.1 aKuales, G.1 aPfister, D.1 aWillems, M.1 aEgger, B.1 aSalvenmoser, W.1 aThaler, M.1 aGorny, A., K.1 aHrouda, M.1 aBorgonie, G.1 aLadurner, P.  uhttps://nematodes.myspecies.info/node/12601562nas a2200241   4500008004100000020001400041245014700055210006900202260000800271300001200279490000800291520083200299100001601131700001401147700001401161700001501175700001801190700001701208700001701225700001501242700001701257856004601274       2009                        eng d  a0949-944X00aEmbryonic origins of hull cells in the flatworm Macrostomum lignano through cell lineage analysis: developmental and phylogenetic implications0 aEmbryonic origins of hull cells in the flatworm Macrostomum lign  cAug  a409-4170 v2193 aThe 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.1 aWillems, M.1 aEgger, B.1 aWolff, C.1 aMouton, S.1 aHouthoofd, W.1 aFonderie, P.1 aCouvreur, M.1 aArtois, T.1 aBorgonie, G.  uhttps://nematodes.myspecies.info/node/108