03224nas a2200193   4500008004100000020001400041245010600055210006900161260000800230300001200238490000800250520263900258100001802897700001802915700001502933700001702948700001902965856004602984       2004                        eng d  a0012-160600aThe apical disposition of the Caenorhabditis elegans intestinal terminal web is maintained by LET-4130 aapical disposition of the Caenorhabditis elegans intestinal term  cApr  a448-4560 v2683 aWe wish to understand how organ-specific structures assemble during embryonic development. In the present paper, we consider what determines the subapical position of the terminal web in the intestinal cells of the nematode Caenorhabditis elegans. The terminal web refers to the organelle-depleted, intermediate filament-rich layer of cytoplasm that underlies the apical microvilli of polarized epithelial cells. It is generally regarded as the anchor for actin rootlets protruding from the microvillar cores. We demonstrate that: (i) the widely used monoclonal antibody MH33 reacts (only) with the gut-specific intermediate filament protein encoded by the ifb-2 gene; (ii) IFB-2 protein accumulates near the gut lumen beginning at the lima bean stage of embryogenesis and remains associated with the gut lumen into adulthood; and (iii) as revealed by immunoelectron microscopy, IFB-2 protein is confined to a discrete circumferential subapical layer within the intestinal terminal web (known in nematodes as the "endotube"); this layer joins directly to the apical junction complexes that connect adjacent gut cells. To investigate what determines the disposition of the IFB-2-containing structure as the terminal web assembles during development, RNAi was used to remove the functions of gene products previously shown to be involved in the overall apicobasal polarity of the developing gut cell. Removal of dlg-1, ajm-1, or hmp-1 function has little effect on the overall position or continuity of the terminal web IFB-2-containing layer. In contrast, removal of the function of the let-413 gene leads to a basolateral expansion of the terminal web, to the point where it can now extend around the entire circumference of the gut cell. The same treatment also leads to concordant basolateral expansion of both gut cell cortical actin and the actin-associated protein ERM-1. LET-413 has previously been shown to be basolaterally located and to prevent the basolateral expansion of several individual apical proteins. In the present context, we conclude that LET-413 is also necessary to maintain the entire terminal web or brush border assembly at the apical surface of C elegans gut cells, a dramatic example of the so-called "fence" function ascribed to epithelial cell junctions. On the other hand, LET-413 is not necessary to establish this apical location during early development. Finally, the distance at which the terminal web intermediate filament layer lies beneath the gut cell surface (both apical and basolateral) must be determined independently of apical junction position. (C) 2004 Elsevier Inc. All rights reserved.1 aBossinger, O.1 aFukushige, T.1 aClaeys, M.1 aBorgonie, G.1 aMcGhee, J., D.  uhttps://nematodes.myspecies.info/node/18001797nas a2200205   4500008004100000020001400041245006900055210006900124260000800193300001000201490000800211520122400219100001801443700001701461700001601478700001801494700001601512700001701528856004601545       2003                        eng d  a0012-160600aEmbryonic cell lineage of the marine nematode Pellioditis marina0 aEmbryonic cell lineage of the marine nematode Pellioditis marina  cJun  a57-690 v2583 aWe describe the complete embryonic cell lineage of the marine nematode Pellioditis marina (Rhabditidae) up to somatic muscle contraction, resulting in the formation of 638 cells, of which 67 undergo programmed cell death. In comparison with Caenorhabditis elegans, the overall lineage homology is 95.5%; fate homology, however, is only 76.4%. The majority of the differences in fate homology concern nervous, epidermal, and pharyngeal tissues. Gut and, remarkably, somatic muscle is highly conserved in number and position. Partial lineage data from the slower developing Halicephalobus sp. (Panagrolaimidae) reveal a lineage largely, but not exclusively, built up of monoclonal sublineage blocs with identical fates, unlike the polyclonal fate distribution in C elegans and P. marina. The fate distribution pattern in a cell lineage could be a compromise between minimizing the number of specification events by monoclonal specification and minimizing the need for migrations by forming the cells close at their final position. The latter could contribute to a faster embryonic development. These results reveal that there is more than one way to build a nematode. (C) 2003 Elsevier Science (USA). All rights reserved.1 aHouthoofd, W.1 aJacobsen, K.1 aMertens, C.1 aVangestel, S.1 aCoomans, A.1 aBorgonie, G.  uhttps://nematodes.myspecies.info/node/18302162nas 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/125