DOCSLIB.ORG

Spoltud-1 Is a Chromatoid Body Component Required for Planarian Long-Term Stem Cell Self-Renewal

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Spoltud-1 Is a Chromatoid Body Component Required for Planarian Long-Term Stem Cell Self-Renewal View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Developmental Biology 328 (2009) 410–421 Contents lists available at ScienceDirect Developmental Biology journal homepage: www.elsevier.com/developmentalbiology Spoltud-1 is a chromatoid body component required for planarian long-term stem cell self-renewal Jordi Solana a,⁎, Paul Lasko b, Rafael Romero a a Departament de Genètica, Facultat de Biologia, Av. Diagonal 645, Edifici Annex, Planta 1, 08028 Barcelona, Catalunya, Spain b Department of Biology and Developmental Biology Research Initiative, McGill University, 1205 Avenue Docteur Penfield, Montreal, Quebec, Canada H3A 1B1 article info abstract Article history: Freshwater planarians exhibit a striking power of regeneration, based on a population of undifferentiated Received for publication 20 October 2008 totipotent stem cells, called neoblasts. These somatic stem cells have several characteristics resembling those Revised 29 January 2009 of germ line stem cells in other animals, such as the presence of perinuclear RNA granules (chromatoid Accepted 30 January 2009 bodies). We have isolated a Tudor domain-containing gene in the planarian species Schmidtea polychroa, Available online 9 February 2009 Spoltud-1, and show that it is expressed in neoblast cells, germ line cells and central nervous system, and during embryonic development. Within the neoblasts, Spoltud-1 protein is enriched in chromatoid bodies. Keywords: Planarian Spoltud-1 RNAi eliminates protein expression after 3 weeks, and abolishes the power of regeneration of Schmidtea polychroa planarians after 7 weeks. Neoblast cells are eliminated by the RNAi treatment, disappearing at the end rather Stem cells than gradually during the process. Neoblasts with no detectable Spoltud-1 protein are able to proliferate and Neoblasts differentiate. These results suggest that Spoltud-1 is required for long term stem cell self renewal. Regeneration © 2009 Elsevier Inc. All rights reserved. Tudor Nuage Chromatoid bodies Germ line Introduction A particular hallmark of neoblast cells is the presence of structures called chromatoid bodies, electron-dense perinuclear granules com- Planarian flatworms have an impressive power of regeneration. An posed of RNA and protein (Coward, 1974; Hori, 1982; Morita and Best, undifferentiated population of totipotent stem cells known as 1984; Morita et al., 1969). Chromatoid bodies are also present in neoblasts underlies this process (Baguñà et al., 1989; Handberg- planarian germ cells and in blastomeres during embryonic develop- Thorsager et al., 2008; Rossi et al., 2008; Sanchez Alvarado and Kang, ment (Cardona et al., 2005b, 2006) and resemble germ granules, often 2005). These cells are able to give rise to all differentiated cell types in called nuage, present in germ line cells from most animals (Eddy, the adult planarian and are maintained throughout the animal's life. 1975; Raz, 2000; Saffman and Lasko, 1999). The presence of these Neoblasts are defined on the basis of their proliferative capabilities structures not only in the germ line but in totipotent somatic stem and their morphological features, such as lack of differentiated cells suggest a role for chromatoid bodies in establishing or structures, relatively uncondensed chromatin and high nucleocyto- maintaining totipotency or an undifferentiated state (Auladell et al., plasmic ratio. Neoblasts are scattered throughout the mesenchyme of 1993). However, the precise role of chromatoid bodies in planarian the animal with the exception of the pharynx, located in the central stem cell biology is not clear yet. region of the body, and the region anterior to the photoreceptors. Interestingly, apparent orthologues of several genes that encode Analysis of proliferation markers such as PCNA immunohistochem- components of nuage, or that required for germ line establishment in istry (Orii et al., 2005), mcm2 in situ hybridization (Salvetti et al., more complex metazoans, are required for planarian neoblast 2000), anti-phospho-histone 3, and bromodeoxyuridine labeling function. Smed-bruno-like (bruli) is a RNA-binding protein that has (Newmark and Sanchez Alvarado, 2000) show a similar pattern to been recently shown to be required for stem cell maintenance in the that of neoblasts, since they are the only proliferative cell type in planarian Schmidtea mediterranea (Guo et al., 2006). Previously, two asexual planarians. Furthermore, neoblasts and all these markers are genes belonging to the PIWI/Argonaute family, smedwi-1 and specifically eliminated after high doses of irradiation, a behavior smedwi-2 were identified in the same species, and smedwi-2 was typical of proliferative cells. Thus, proliferation markers are a powerful directly implicated in neoblast differentiation control (Reddien et al., tool in order to identify neoblast cells. 2005). An additional piwi gene with a similar function, smedwi-3, has been recently found (Palakodeti et al., 2008). A pumilio homologue, ⁎ Corresponding author. DjPum, was found in the planarian Dugesia japonica, and was also E-mail addresses: [email protected], [email protected] (J. Solana). shown to be involved in planarian stem cell biology (Salvetti et al., 0012-1606/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.ydbio.2009.01.043 J. Solana et al. / Developmental Biology 328 (2009) 410–421 411 2005). All of these genes are expressed in mesenchymal cells with a tertiary structure, and on the basis of their reciprocal blast hits to pattern similar to that of neoblasts and in the germ line, and abolish Drosophila tudor and mammalian TDRD1 and TDRD6 we finally regeneration capacity when inhibited through RNAi. selected spoltud-1 and spoltud-2 for further experiments (Accession In Drosophila melanogaster, the germ line is specified through numbers FJ655915 and FJ655916, respectively). We designed specific preformation (Extavour and Akam, 2003), meaning that it depends primers against S. mediterranea and used them to amplify the genes in upon the formation of a specialized cytoplasm that is derived from the a S. polychroa cDNA, made from total RNA using MMLV reverse products of genes expressed maternally during oogenesis. In Droso- transcriptase (Promega). In order to obtain the full cDNA sequence of phila, oskar RNA accumulates at the posterior pole of the developing spoltud-1 RACE reactions were carried out adding a poly-A tail to the oocyte, and nucleates the formation of pole plasm, which shares cDNA with TdT enzyme (New England Biolabs) and amplifying it by several components with nuage. Vasa and Tudor proteins are localized PCR by means of an anchor primer. The list and position of primers in this region in an Oskar-dependent manner and, like Oskar, both are used (5′–3′) are indicated in Fig. S1. Probes for Spoltud-1 in situ essential for germ line specification (Boswell and Mahowald, 1985; hybridization were generated from primers 3 and 4, dsRNA for RNAi Lasko and Ashburner, 1988). No homologue of oskar has been found in was generated from primers 1 and 2. a non-dipteran species so far. However, a PL10 gene (closely related to vasa) was identified in the planarian species D. japonica, and its In situ hybridization expression is described to be enriched in mesenchymal neoblasts (Shibata et al., 1999). Whole mount in situ hybridizations and in situ hybridization on Tudor contains a number of repeated elements called Tudor paraffin sections were carried out as described previously (Cardona et domains (Thomson and Lasko, 2005). Different Tudor domain- al., 2005a; Umesono et al., 1997; Zayas et al., 2005). Fluorescent in situ containing proteins have been described in mice and humans and, hybridizations were incubated overnight with either antidigoxigenin- among them, TDRD1, TDRD6 and TDRD7 have been shown to have a POD or antibiotin-POD (Roche) at a 1:100 dilution and developed with role in the germ line (Chuma et al., 2006; Hosokawa et al., 2007) TSA system (Perkin Elmer). For double fluorescent in situ hybridiza- although their orthology relationships are not clear. The Tudor domain tions slides were treated with 1% H2O2 in PBS for 1 h and washed 6 binds symmetrical dimethylated arginines (Cote and Richard, 2005), times for 15 min in PBS after first development prior to incubating and in D. melanogaster Tudor interacts with Valois, a component of the with the second POD-labeled antibody. When in situ hybridization methylosome (Anne et al., 2007). Some protein arginine methyl- was followed by immunohistochemistry permeabilization was carried transferases such as capsuleen in D. melanogaster and its homologue in out by heating the slides at 95 °C for 20 min in citrate buffer (10 mM mouse, PRMT5, have been demonstrated to have a role in germ line sodium citrate, 0.05% Tween 20, pH 6.0). formation (Ancelin et al., 2006; Anne et al., 2007), suggesting that Tudor domains and symmetrical dimethylated arginines could have a Immunohistochemistry crucial role in germ line biology. Due to the close relationship between the metazoan germ line and Slides were permeabilized with 0.4% pepsin in 0.1 N HCl at 37 °C or planarian stem cells we performed Tudor domain searches in as described above, blocked in 5% non-fat dry milk in PBS 0.05% Tween planarian databases in order to check their possible roles in neoblast 20, incubated overnight with primary antibodies in blocking solution, cells. Here we present the isolation of spoltud-1, a Tudor domain- washed in PBS 0.05 Tween 20,
Load more

Recommended publications
  • Distribution of Proliferating Cells and Vasa-Positive Cells in the Embryo of Macrostomum Lignano (Rhabditophora, Platyhelminthes)
    Belg. J. Zool., 140 (Suppl.): 149-153 July 2010 Distribution of proliferating cells and vasa-positive cells in the embryo of Macrostomum lignano (Rhabditophora, Platyhelminthes) Maxime Willems1, Marjolein Couvreur1, Mieke Boone1, Wouter Houthoofd1 and Tom Artois2 1 Nematology Section, Department of Biology, Ghent University, K. L. Ledeganckstraat 35, B-9000 Ghent, Belgium. 2 Centre for Environmental Sciences, Research group Zoology: Biodiversity & Toxicology, Hasselt University, Agoralaan, Gebouw D, B-3590 Belgium Corresponding author: Maxime Willems; email: [email protected] 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 Mac- rostomum 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 embry- onic 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.
    [Show full text]
  • Identification of Genes Needed for Regeneration, Stem Cell Function, and Tissue Homeostasis by Systematic Gene Perturbation in Planaria
    Developmental Cell, Vol. 8, 635–649, May, 2005, Copyright ©2005 by Elsevier Inc. DOI 10.1016/j.devcel.2005.02.014 Identification of Genes Needed for Regeneration, Stem Cell Function, and Tissue Homeostasis by Systematic Gene Perturbation in Planaria Peter W. Reddien, Adam L. Bermange,1,2 number of attributes not manifested by current ecdyso- Kenneth J. Murfitt,1 Joya R. Jennings, zoan model systems (e.g., C. elegans and Drosophila), and Alejandro Sánchez Alvarado* such as regeneration and adult somatic stem cells. Department of Neurobiology and Anatomy Therefore, studies of planarian biology will help the un- University of Utah School of Medicine derstanding of processes relevant to human develop- 401 MREB, 20N 1900E ment and health not easily studied in current inverte- Salt Lake City, Utah 84132 brate genetic systems. Neoblasts are the only known proliferating cells in adult planarians and reside in the parenchyma. Follow- Summary ing injury, a neoblast proliferative response is triggered, generating a regeneration blastema consisting of ini- Planarians have been a classic model system for the tially undifferentiated cells covered by epidermal cells. study of regeneration, tissue homeostasis, and stem Moreover, essentially all tissues in adult planarians turn cell biology for over a century, but they have not his- over and are replaced by neoblast progeny. Although torically been accessible to extensive genetic ma- the characteristics and diversity of the neoblasts still nipulation. Here we utilize RNA-mediated genetic await careful molecular elucidation, neoblasts may be interference (RNAi) to introduce large-scale gene in- totipotent stem cells (Reddien and Sánchez Alvarado, hibition studies to the classic planarian system.
    [Show full text]
  • The PIWI Proteins SMEDWI-2 and SMEDWI-3 Are Required for Stem Cell Function and Pirna Expression in Planarians
    JOBNAME: RNA 14#6 2008 PAGE: 1 OUTPUT: Wednesday May 7 22:53:43 2008 csh/RNA/152282/rna10850 Downloaded from rnajournal.cshlp.org on October 1, 2021 - Published by Cold Spring Harbor Laboratory Press The PIWI proteins SMEDWI-2 and SMEDWI-3 are required for stem cell function and piRNA expression in planarians DASARADHI PALAKODETI,1 MAGDA SMIELEWSKA,1 YI-CHIEN LU,1 GENE W. YEO,2 and BRENTON R. GRAVELEY1 1Department of Genetics and Developmental Biology, University of Connecticut Stem Cell Institute, University of Connecticut Health Center, Farmington, Connecticut 06030-3301, USA 2Crick–Jacobs Center for Theoretical and Computational Biology, Salk Institute, La Jolla, California 92037, USA ABSTRACT PIWI proteins are expressed in germ cells in a wide variety of metazoans, where they participate in the synthesis and function of a novel class of small RNAs called PIWI associated RNAs (piRNAs). One function of piRNAs is to preserve the integrity of the germline genome by silencing transposons, though they also participate in epigenetic and post-transcriptional gene regulation. In the planarian Schmidtea mediterranea, the PIWI proteins SMEDWI-1 and SMEDWI-2 are expressed in neoblasts and SMEDWI-2 is required for regeneration and homeostasis. Here, we identify a diverse population of ;32-nucleotide small RNAs that strongly resemble vertebrate and insect piRNAs and map to hundreds of thousands of loci in the S. mediterranea genome. The expression of these RNAs occurs predominantly in neoblasts and is not restricted to the germline. RNAi knockdown of either SMEDWI-2 or a newly identified PIWI protein, SMEDWI-3, impairs regeneration and homeostasis and decreases the levels of both piRNAs and neoblasts.
    [Show full text]
  • The Genome of Schmidtea Mediterranea and the Evolution Of
    OPEN ArtICLE doi:10.1038/nature25473 The genome of Schmidtea mediterranea and the evolution of core cellular mechanisms Markus Alexander Grohme1*, Siegfried Schloissnig2*, Andrei Rozanski1, Martin Pippel2, George Robert Young3, Sylke Winkler1, Holger Brandl1, Ian Henry1, Andreas Dahl4, Sean Powell2, Michael Hiller1,5, Eugene Myers1 & Jochen Christian Rink1 The planarian Schmidtea mediterranea is an important model for stem cell research and regeneration, but adequate genome resources for this species have been lacking. Here we report a highly contiguous genome assembly of S. mediterranea, using long-read sequencing and a de novo assembler (MARVEL) enhanced for low-complexity reads. The S. mediterranea genome is highly polymorphic and repetitive, and harbours a novel class of giant retroelements. Furthermore, the genome assembly lacks a number of highly conserved genes, including critical components of the mitotic spindle assembly checkpoint, but planarians maintain checkpoint function. Our genome assembly provides a key model system resource that will be useful for studying regeneration and the evolutionary plasticity of core cell biological mechanisms. Rapid regeneration from tiny pieces of tissue makes planarians a prime De novo long read assembly of the planarian genome model system for regeneration. Abundant adult pluripotent stem cells, In preparation for genome sequencing, we inbred the sexual strain termed neoblasts, power regeneration and the continuous turnover of S. mediterranea (Fig. 1a) for more than 17 successive sib- mating of all cell types1–3, and transplantation of a single neoblast can rescue generations in the hope of decreasing heterozygosity. We also developed a lethally irradiated animal4. Planarians therefore also constitute a a new DNA isolation protocol that meets the purity and high molecular prime model system for stem cell pluripotency and its evolutionary weight requirements of PacBio long-read sequencing12 (Extended Data underpinnings5.
    [Show full text]
  • A Spatiotemporal Characterisation of Redox Molecules in Planarians, with a Focus on the Role of Glutathione During Regeneration
    biomolecules Article A Spatiotemporal Characterisation of Redox Molecules in Planarians, with a Focus on the Role of Glutathione during Regeneration Karolien Bijnens † , Vincent Jaenen † , Annelies Wouters , Nathalie Leynen , Nicky Pirotte, Tom Artois and Karen Smeets * Centre for Environmental Sciences, Zoology, Biodiversity and Toxicology, Hasselt University, Agoralaan D, 3590 Diepenbeek, Belgium; [email protected] (K.B.); [email protected] (V.J.); [email protected] (A.W.); [email protected] (N.L.); [email protected] (N.P.); [email protected] (T.A.) * Correspondence: [email protected] † These authors contributed equally. Abstract: A strict coordination between pro- and antioxidative molecules is needed for normal animal physiology, although their exact function and dynamics during regeneration and devel- opment remains largely unknown. Via in vivo imaging, we were able to locate and discriminate between reactive oxygen species (ROS) in real-time during different physiological stages of the highly regenerative planarian Schmidtea mediterranea. All ROS signals were strong enough to overcome the detected autofluorescence. Combined with an in situ characterisation and quantification of the transcription of several antioxidant genes, our data showed that the planarian gut and epidermis Citation: Bijnens, K.; Jaenen, V.; have a well-equipped redox system. Pharmacological inhibition or RNA interference of either side Wouters, A.; Leynen, N.; Pirotte, N.; of the redox balance resulted
    [Show full text]
  • The Planarian Prometheus, Quantified
    RESEARCH HIGHLIGHTS SENSORS AND PROBES Together we shine A dimerization-dependent red fluorescent protein provides a new strategy for biosensor design. + Robert Campbell and members of his laboratory at the University of Alberta, Edmonton, focus on engineering fluores- cent protein–based indicators for imaging biological processes such as the detection of protein-protein interactions, enzyme activities or changes in small-molecule concentrations. Typically, the design of biosensors for these types of applica- tions relies on one of three principles: modulation of fluorescence resonance energy transfer between two fluorescent proteins, Schema of ddRFP’s mode of changes in fluorescence intensity of a single fluorescent protein or action. Image courtesy of its reconstruction from two split halves. All these strategies have S.C. Alford. been most commonly applied to build green or yellow fluorescent sensors; their red counterparts have proven much harder to engineer or to get to work. Making sensors shine in the blood-colored side of the spectrum could offer advantages for in vivo imaging and would enable combinatorial experiments using different hue-emitting sensors. One thing that might explain the difficult ‘behavior’ of red fluorescent proteins is their tendency to exist as multiunit proteins. This gregarious property is in many cases undesirable from the engineering standpoint and many efforts have aimed at converting them into monomeric or dimeric variants. To Campbell, however, it became apparent that the oligomeric nature of red fluorescent proteins was precisely what made them bright. So instead of engineering this property out, he figured out a way of exploiting it. “The dimerization-dependent brightness [that STEM CELLS The pLaNarIaN PrOMetheUs, QUaNtIFIeD Tools to study stem cell function in planarians continue to accumulate.
    [Show full text]
  • Are Planaria Individuals? What Regenerative Biology Is Telling Us About the Nature of Multicellularity
    1 of 18 Evolutionary Biology (accepted) Are planaria individuals? What regenerative biology is telling us about the nature of multicellularity Chris Fields1 and Michael Levin2 123 Rue des Lavandières, 11160 Caunes Minervois, France [email protected] ORCID: 0000-0002-4812-0744 2Allen Discovery Center at Tufts University, Medford, MA 02155 USA [email protected] ORCID: 0000-0001-7292-8084 Running Title: Are planaria individuals? Abstract Freshwater planaria (Platyhelminthes, Turbellaria, Tricladida) pose a challenge to current concepts of biological individuality. We review molecular and developmental evidence suggesting that mature intact planaria are not biological individuals but their totipotent stem cells (neoblasts) are individuals. Neoblasts within a single planarian body are, in particular, genetically heterogeneous, migratory, effectively immortal, and effectively autonomous. They cooperate to maintain the planarian body as an obligate environment but compete to make this environment maximally conducive to the survival of their own neoblast lineages. These results suggest that planaria have not fully completed the transition to multicellularity, but instead represent an intermediate form in which a small number of genetically- heterogeneous, reproductively-competent cells effectively “farm” their reproductively-incompetent offspring. Keywords: Bioelectricity; Cooperation; Dugesia japonica; Dugesia ryukyuensis; Germ cells; Girardia tigrina; Regeneration; Schmidtea mediterranea; Stem cells 2 of 18 Introduction The major evolutionary transitions, including those from prokaryotes to eukaryotes and from free- living cells to multicellularity, all increase the scale over which cooperative interactions dominate competitive interactions (Maynard Smith and Szathmáry, 1995; Szathmáry, 2015; West, Fisher, Gardner and Kiers, 2015). These evolutionary transitions have transformed the biosphere, subjugating the activity of unicellular organisms in favor of the goals of composite entities: multicellular bodies, e.g.
    [Show full text]
  • Download PDF of This Story
    MASTER OF REGENERATION ¤ by Kendall Powell Once a high school biology oddity, planarians illustration by Jason Holley are moving into the spotlight to reveal secrets of self-renewal. As the plane touched down in Barcelona on a Saturday afternoon in September 1998, Alejandro Sánchez Alvarado was excited to see the runway pavement slick from a recent rainfall. Rain would have filled up the abandoned fountains in Parc de Montjuïc where he and Phil Newmark hoped to trap their quarry. » August 2o1o | HHMI BULLETIN 29 works, shouldn’t we be using the master of The conventional thinking at the time was THE TWO regeneration, the planarian? It’s a simple that regeneration was simply a recapitula- flatworm with rudimentary eyes, brain, tion of embryonic development pathways. HURRIED gut, and gonads but no circulatory or respi- That logic never sat right with Sánchez ratory systems. A fraction of the worm, Alvarado. IN A CAB 1/279th or just 0.3 percent, can regenerate “If animals are just redoing embryolog- TO THE a whole new animal. Cut off its head, a ical developmental events, then everyone new one grows back within 10 days. should do it. And we wouldn’t care as NEAREST Aside from its capacity to self-renew, much about having health insurance the planarian is a beguiling creature with plans,” he says. “Instead, you are asking an BUTCHER its googley-eyed cartoonish look con- adult animal to form a de novo structure trasted with a gliding swimming elegance. within an adult context.” FOR A SLAB But when these researchers started, the After reading Morgan’s 1901 book animal had only a handful of identified Regeneration, Sánchez Alvarado was OF SHEEP’S genes.
    [Show full text]
  • Identifying Genes Involved in Suppression of Tumor Formation in the Planarian Schmidtea Mediterranea
    Best Integrated Writing Volume 2 Article 6 2015 Identifying Genes Involved in Suppression of Tumor Formation in the Planarian Schmidtea mediterranea Erin Dorsten Wright State University Follow this and additional works at: https://corescholar.libraries.wright.edu/biw Part of the American Literature Commons, Ancient, Medieval, Renaissance and Baroque Art and Architecture Commons, Applied Behavior Analysis Commons, Business Commons, Classical Archaeology and Art History Commons, Comparative Literature Commons, English Language and Literature Commons, Gender and Sexuality Commons, International and Area Studies Commons, Medicine and Health Sciences Commons, Modern Literature Commons, Nutrition Commons, Race, Ethnicity and Post-Colonial Studies Commons, Religion Commons, and the Women's Studies Commons Recommended Citation Dorsten, E. (2015). Identifying Genes Involved in Suppression of Tumor Formation in the Planarian Schmidtea mediterranea, Best Integrated Writing, 2. This Article is brought to you for free and open access by CORE Scholar. It has been accepted for inclusion in Best Integrated Writing by an authorized editor of CORE Scholar. For more information, please contact library- [email protected]. ERIN DORSTEN BIO 4020 Best Integrated Writing: Journal of Excellence in Integrated Writing Courses at Wright State Fall 2015 (Volume 2) Article #5 Identifying Genes Involved in Suppression of Tumor Formation in the Planarian Schmidtea mediterranea ERIN DORSTEN BIO 4020-02: Current Literature: Biology of Regeneration Fall 2014 Dr. Labib Rouhana Dr. Rouhana notes that students were challenged to write a scientific proposal centered in the study of regenerative organisms. This proposal describes experiments designed to identify genes involved in protecting an organism with negligible senescence from tumor formation. Ms. Dorsten was able to formulate a proposal of outstanding quality with regards to both literary competency and scientific creativity.
    [Show full text]
  • Neoblast Specialization in Regeneration of the Planarian
    Please cite this article in press as: Scimone et al., Neoblast Specialization in Regeneration of the Planarian Schmidtea mediterranea, Stem Cell Reports (2014), http://dx.doi.org/10.1016/j.stemcr.2014.06.001 Stem Cell Reports Article Neoblast Specialization in Regeneration of the Planarian Schmidtea mediterranea M. Lucila Scimone,1,2 Kellie M. Kravarik,1,2 Sylvain W. Lapan,1,2 and Peter W. Reddien1,* 1Howard Hughes Medical Institute, MIT Biology, and Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA 2Co-first author *Correspondence: [email protected] http://dx.doi.org/10.1016/j.stemcr.2014.06.001 This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). SUMMARY Planarians can regenerate any missing body part in a process requiring dividing cells called neoblasts. Historically, neoblasts have largely been considered a homogeneous stem cell population. Most studies, however, analyzed neoblasts at the population rather than the single-cell level, leaving the degree of heterogeneity in this population unresolved. We combined RNA sequencing of neoblasts from wounded planarians with expression screening and identified 33 transcription factors transcribed in specific differentiated cells and in small fractions of neoblasts during regeneration. Many neoblast subsets expressing distinct tissue-associated transcription factors were present, suggesting candidate specification into many lineages. Consistent with this possibility, klf, pax3/7, and FoxA were required for the differentiation of cintillo-expressing sensory neurons, dopamine-b-hydroxylase-expressing neurons, and the pharynx, respectively. Together, these results suggest that specification of cell fate for most-to-all regenerative lineages occurs within neoblasts, with regenera- tive cells of blastemas being generated from a highly heterogeneous collection of lineage-specified neoblasts.
    [Show full text]
  • Fundamentals of Planarian Regeneration
    3 Sep 2004 16:54 AR AR226-CB20-26.tex AR226-CB20-26.sgm LaTeX2e(2002/01/18) P1: GCE 10.1146/annurev.cellbio.20.010403.095114 Annu. Rev. Cell Dev. Biol. 2004. 20:725–57 doi: 10.1146/annurev.cellbio.20.010403.095114 Copyright c 2004 by Annual Reviews. All rights reserved First published online as a Review in Advance on July 2, 2004 FUNDAMENTALS OF PLANARIAN REGENERATION PeterW.Reddien and Alejandro Sanchez´ Alvarado University of Utah School of Medicine, Department of Neurobiology and Anatomy, Salt Lake City, Utah 84132-3401; email: [email protected], [email protected] KeyWords stem cells, blastema, epimorphosis, morphallaxis, flatworm ■ Abstract The principles underlying regeneration in planarians have been ex- plored for over 100 years through surgical manipulations and cellular observations. Planarian regeneration involves the generation of new tissue at the wound site via cell proliferation (blastema formation), and the remodeling of pre-existing tissues to re- store symmetry and proportion (morphallaxis). Because blastemas do not replace all tissues following most types of injuries, both blastema formation and morphallaxis are needed for complete regeneration. Here we discuss a proliferative cell population, the neoblasts, that is central to the regenerative capacities of planarians. Neoblasts may be a totipotent stem-cell population capable of generating essentially every cell type in the adult animal, including themselves. The population properties of the neoblasts and their descendants still await careful elucidation. We identify the types of structures produced by blastemas on a variety of wound surfaces, the principles guiding the re- organization of pre-existing tissues, and the manner in which scale and cell number proportions between body regions are restored during regeneration.
    [Show full text]
  • Multicellularity, Stem Cells, and the Neoblasts of the Planarian Schmidtea Mediterranea
    Experimental Cell Research 306 (2005) 299 – 308 www.elsevier.com/locate/yexcr Review Multicellularity, stem cells, and the neoblasts of the planarian Schmidtea mediterranea Alejandro Sa´nchez Alvarado*, Hara Kang University of Utah School of Medicine, Department of Neurobiology and Anatomy, Salt Lake City, UT 84112, USA Received 4 March 2005, revised version received 4 March 2005 Available online 25 April 2005 Abstract All multicellular organisms depend on stem cells for their survival and perpetuation. Their central role in reproductive, embryonic, and post- embryonic processes, combined with their wide phylogenetic distribution in both the plant and animal kingdoms intimates that the emergence of stem cells may have been a prerequisite in the evolution of multicellular organisms. We present an evolutionary perspective on stem cells and extend this view to ascertain the value of current comparative studies on various invertebrate and vertebrate somatic and germ line stem cells. We suggest that somatic stem cells may be ancestral, with germ line stem cells being derived later in the evolution of multicellular organisms. We also propose that current studies of stem cell biology are likely to benefit from studying the somatic stem cells of simple metazoans. Here, we present the merits of neoblasts, a largely unexplored, yet experimentally accessible population of stem cells found in the planarian Schmidtea mediterranea. We introduce what we know about the neoblasts, and posit some of the questions that will need to be addressed in order to better resolve the relationship between planarian somatic stem cells and those found in other organisms, including humans. D 2005 Elsevier Inc.
    [Show full text]