The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Kiyokazu Agata - One of the best experts on this subject based on the ideXlab platform.
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a subtractive facs method for isolation of Planarian stem cells and neural cells
Methods of Molecular Biology, 2018Co-Authors: Tetsutaro Hayashi, Kiyokazu AgataAbstract:: Planarians are among the metazoan organisms with the greatest regenerative abilities. This ability is based on their pluripotent stem cells, called neoblasts, which constitute 10-20% of the cells in their body. Elucidating the molecular mechanisms of the Planarian stem cell system, for example, the maintenance of stem cell homeostasis and orchestration of lineage choices, contributes powerfully to the advancement of regenerative biology. Our group has developed fluorescence activated cell sorting (FACS) methodologies for the reliable isolation of Planarian stem cells, which constitutes an important experimental asset in the field. Here, we describe detailed protocols for the isolation of (1) Planarian stem cells and (2) neural cells. Planarian stem cells are isolated by subtraction of the FACS profiles of intact and γ-ray-irradiated (= stem cell depleted) animals stained with Hoechst 33342 and Calcein AM. The neural cells are isolated by subtracting the FACS profiles of head and tail fragments stained with Hoechst 33258 and Merocyanine 540.
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heterogeneity of chromatoid bodies in adult pluripotent stem cells of Planarian dugesia japonica
Development Growth & Differentiation, 2016Co-Authors: Makoto Kashima, Kiyokazu Agata, Nobuyoshi Kumagai, Norito ShibataAbstract:The robust regenerative ability of Planarians is known to be dependent on adult pluripotent stem cells called neoblasts. One of the morphological features of neoblasts is cytoplasmic ribonucleoprotein granules (chromatoid bodies: CBs), which resemble germ granules present in germline cells in other animals. Previously, we showed by immuno-electron microscopic analysis that DjCBC-1, a Planarian Me31B/Dhh1/DDX6 homologue, which is a component of ribonucleoprotein granules, was localized in CBs in the Planarian Dugesia japonica. Also, recently it was reported using another Planarian species that Y12 antibody recognizing symmetrical dimethylarginine (sDMA) specifically binds to CBs in which histone mRNA is co-localized. Here, we showed by double immunostaining and RNA interference (RNAi) that DjCBC-1-containing CBs and Y12-immunoreactive CBs are distinct structures, suggesting that CBs are composed of heterogeneous populations. We also found that the Y12-immunoreactive CBs specifically contained a cytoplasmic type of Planarian PIWI protein (DjPiwiC). We revealed by RNAi experiments that Y12-immunoreactive CBs may have anti-transposable element activity involving the DjPiwiC protein in the neoblasts.
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unusually large number of mutations in asexually reproducing clonal Planarian dugesia japonica
PLOS ONE, 2015Co-Authors: Osamu Nishimura, Yoshihiko Umesono, Takeshi Inoue, Tetsutaro Hayashi, Kazutaka Hosoda, Eri Kawaguchi, Shigenobu Yazawa, Kiyokazu AgataAbstract:We established a laboratory clonal strain of freshwater Planarian (Dugesia japonica) that was derived from a single individual and that continued to undergo autotomous asexual reproduction for more than 20 years, and we performed large-scale genome sequencing and transcriptome analysis on it. Despite the fact that a completely clonal strain of the Planarian was used, an unusually large number of mutations were detected. To enable quantitative genetic analysis of such a unique organism, we developed a new model called the Reference Gene Model, and used it to conduct large-scale transcriptome analysis. The results revealed large numbers of mutations not only outside but also inside gene-coding regions. Non-synonymous SNPs were detected in 74% of the genes for which valid ORFs were predicted. Interestingly, the high-mutation genes, such as metabolism- and defense-related genes, were correlated with genes that were previously identified as diverse genes among different Planarian species. Although a large number of amino acid substitutions were apparently accumulated during asexual reproduction over this long period of time, the Planarian maintained normal body-shape, behaviors, and physiological functions. The results of the present study reveal a unique aspect of asexual reproduction.
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comparative transcriptome analysis between Planarian dugesia japonica and other platyhelminth species
BMC Genomics, 2012Co-Authors: Osamu Nishimura, Yukako Hirao, Hiroshi Tarui, Kiyokazu AgataAbstract:Planarians are considered to be among the extant animals close to one of the earliest groups of organisms that acquired a central nervous system (CNS) during evolution. Planarians have a bilobed brain with nine lateral branches from which a variety of external signals are projected into different portions of the main lobes. Various interneurons process different signals to regulate behavior and learning/memory. Furthermore, Planarians have robust regenerative ability and are attracting attention as a new model organism for the study of regeneration. Here we conducted large-scale EST analysis of the head region of the Planarian Dugesia japonica to construct a database of the head-region transcriptome, and then performed comparative analyses among related species. A total of 54,752 high-quality EST reads were obtained from a head library of the Planarian Dugesia japonica, and 13,167 unigene sequences were produced by de novo assembly. A new method devised here revealed that proteins related to metabolism and defense mechanisms have high flexibility of amino-acid substitutions within the Planarian family. Eight-two CNS-development genes were found in the Planarian (cf. C. elegans 3; chicken 129). Comparative analysis revealed that 91% of the Planarian CNS-development genes could be mapped onto the schistosome genome, but one-third of these shared genes were not expressed in the schistosome. We constructed a database that is a useful resource for comparative Planarian transcriptome studies. Analysis comparing homologous genes between two Planarian species showed that the potential of genes is important for accumulation of amino-acid substitutions. The presence of many CNS-development genes in our database supports the notion that the Planarian has a fundamental brain with regard to evolution and development at not only the morphological/functional, but also the genomic, level. In addition, our results indicate that the Planarian CNS-development genes already existed before the divergence of Planarians and schistosomes from their common ancestor.
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different requirements for conserved post transcriptional regulators in Planarian regeneration and stem cell maintenance
Developmental Biology, 2010Co-Authors: Labib Rouhana, Osamu Nishimura, Norito Shibata, Kiyokazu AgataAbstract:Planarian regeneration depends on the presence and precise regulation of pluripotent adult somatic stem cells named neoblasts, which differentiate to replace cells of any missing tissue. A characteristic feature of neoblasts is the presence of large perinuclear nonmembranous organelles named "chromatoid bodies", which are comparable to ribonucleoprotein structures found in germ cells of organisms across different phyla. In order to better understand regulation of gene expression in neoblasts, and potentially the function and composition of chromatoid bodies, we characterized homologues to known germ and soma ribonucleoprotein granule components from other organisms and analyzed their function during regeneration of the Planarian Dugesia japonica. Expression in neoblasts was detected for 49 of 55 analyzed genes, highlighting the prevalence of post-transcriptional regulation in Planarian stem cells. RNAi-mediated knockdown of two factors [ago-2 and bruli] lead to loss of neoblasts, and consequently loss of regeneration, corroborating with results previously reported for a bruli ortholog in the Planarian Schmidtea mediterranea (Guo et al., 2006). Conversely, depletion mRNA turnover factors [edc-4 or upf-1], exoribonucleases [xrn-1 or xrn-2], or DEAD box RNA helicases [Djcbc-1 or vas-1] inhibited Planarian regeneration, but did not reduce neoblast proliferation or abundance. We also found that depletion of cap-dependent translation initiation factors eIF-3A or eIF-2A interrupted cell cycle progression outside the M-phase of mitosis. Our results show that a set of post-transcriptional regulators is required to maintain the stem cell identity in neoblasts, while another facilitates proper differentiation. We propose that Planarian neoblasts maintain pluripotency by employing mechanisms of post-transcriptional regulation exhibited in germ cells and early development of most metazoans.
Michael Levin - One of the best experts on this subject based on the ideXlab platform.
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effects of ivermectin exposure on regeneration of d dorotocephala Planaria exploiting human approved ion channel drugs as morphoceuticals
Macromolecular Bioscience, 2019Co-Authors: Nina N Ferenc, Michael LevinAbstract:Transformative applications in regenerative medicine await increased control of processes implementing repair and remodeling of complex living structures. Recent work reveals ion channel drugs as a powerful toolkit for modulating endogenous bioelectric circuits that control growth and form in vivo and in vitro. It is therefore especially important to develop assays in model systems that will enable the testing of these "morphoceuticals"-compounds with predictable effects on anatomical structure. The regenerative Planaria are an ideal model system for this purpose. Several studies have shown a role for bioelectric signaling in Planarian regeneration, but these have focused on Dugesia japonica and Schmidtea mediterranea. It is not known how the alterations of ion channel activity would affect regeneration in other species of Planaria-an important aspect of building robust computational models of bioelectric circuits. Here, the effect of ivermectin (IVM), a chloride channel opener drug commonly used to combat heartworm is tested, on regeneration in a new species of Planaria: Dugesia dorotocephala. Exposure to IVM during regeneration results in patterning abnormalities, such as bifurcated tails with partial heads, as well as delayed regeneration. These data extend our understanding of the effects of human-approved ion channel drugs on regenerative processes.
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Neural control of body-plan axis in regenerating Planaria.
Public Library of Science (PLoS), 2019Co-Authors: Alexis Pietak, Johanna Bischof, Joshua Lapalme, Junji Morokuma, Michael LevinAbstract:Control of axial polarity during regeneration is a crucial open question. We developed a quantitative model of regenerating Planaria, which elucidates self-assembly mechanisms of morphogen gradients required for robust body-plan control. The computational model has been developed to predict the fraction of heteromorphoses expected in a population of regenerating Planaria fragments subjected to different treatments, and for fragments originating from different regions along the anterior-posterior and medio-lateral axis. This allows for a direct comparison between computational and experimental regeneration outcomes. Vector transport of morphogens was identified as a fundamental requirement to account for virtually scale-free self-assembly of the morphogen gradients observed in Planarian homeostasis and regeneration. The model correctly describes altered body-plans following many known experimental manipulations, and accurately predicts outcomes of novel cutting scenarios, which we tested. We show that the vector transport field coincides with the alignment of nerve axons distributed throughout the Planarian tissue, and demonstrate that the head-tail axis is controlled by the net polarity of neurons in a regenerating fragment. This model provides a comprehensive framework for mechanistically understanding fundamental aspects of body-plan regulation, and sheds new light on the role of the nervous system in directing growth and form
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the bacterial metabolite indole inhibits regeneration of the Planarian flatworm dugesia japonica
iScience, 2018Co-Authors: Katherine B Williams, Michael Levin, Benjamin E WolfeAbstract:Summary Planarian flatworms have been used for over a century as models for regeneration. Planarians live in aquatic environments with constant exposure to microbes, but the mechanisms by which bacteria may mediate Planarian regeneration are largely unknown. We characterized the microbiome of laboratory populations of the Planarian Dugesia japonica and determined how individual bacteria impact D. japonica regeneration. Eight to ten taxa in the phyla Bacteroidetes and Proteobacteria consistently occur across Planarian colonies housed in different research laboratories. Individual members of the D. japonica microbiome can delay regeneration including the development of eye spots and blastema formation. The microbial metabolite indole is produced in significant quantities by two bacteria that are consistently found in the D. japonica microbiome and contributes to delays in regeneration. Collectively, these results provide a baseline understanding of the bacteria associated with the Planarian D. japonica and demonstrate how metabolite production by host-associated microbes can affect regeneration.
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Are Planaria Individuals? What Regenerative Biology is Telling Us About the Nature of Multicellularity
Evolutionary Biology, 2018Co-Authors: Chris Fields, Michael LevinAbstract: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.
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effects of ivermectin exposure on regeneration of d dorotocephala Planaria
bioRxiv, 2017Co-Authors: Nina N Ferenc, Michael LevinAbstract:The ability of cells to communicate is essential during pattern formation, as they make decisions that drive growth and form. One mode of cellular signaling is via bioelectrical properties determined by the activity of ion channels. Several studies have shown a role for bioelectric signaling in Planarian regeneration, but these have focused on D. japonica and S. mediterranea. It is not known how the alterations of ion channel activity would affect regeneration in other species of Planaria. Here, we tested the effect of ivermectin (IVM), a chloride channel opener drug commonly used to combat heart worms, on regeneration in a new species of Planaria: D. dorotocephala. Exposure to IVM during regeneration resulted in patterning abnormalities, such as bifurcated tails with partial heads, as well as delayed regeneration. By testing the effect of drugs that target resting potential on regenerative repair in novel model species, additional insight is gained on the comparative roles of ionic signaling across taxa.
Phillip A. Newmark - One of the best experts on this subject based on the ideXlab platform.
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restoration of anterior regeneration in a Planarian with limited regenerative ability
Nature, 2013Co-Authors: James M Sikes, Phillip A. NewmarkAbstract:Although the capacity for tissue regeneration of Planarians is exceptional, Planarians with more limited regenerative capacities are known; this study of Procotyla fluviatilis, a Planarian with restricted ability to replace missing tissues, shows that Wnt signalling is aberrantly regulated in regeneration-deficient tissues and that downregulation of Wnt signalling in these regions restores regenerative abilities, revealing that manipulating a single signalling pathway can reverse the evolutionary loss of regenerative potential. Planarians are flatworms common in streams and ponds whose capacity for tissue regeneration is legendary. But with more limited regenerative capacities are known. Three papers published in Nature this week study Planaria with differing regenerative capacities and identify the Wnt/β-catenin molecular signalling pathway, important in embryonic development and adult homeostasis in multicellular organisms, as central to the regeneration mechanism. Yoshihiko Umesono et al. identify ERK and β-catenin signalling as the basis for a morphogenetic gradient along the anterior–posterior axis that is required for regeneration. These authors also demonstrate that inhibition of β-catenin can rescue head regeneration in Phagocata kawakatsui, a Planarian that otherwise cannot regenerate heads from the posterior pieces. James Sikes and Phillip Newmark show in Procotyla fluviatilis, which has restricted ability to replace missing tissues, that Wnt signalling is aberrantly regulated in regeneration-deficient tissues. Downregulation of Wnt signalling in these regions restores regenerative abilities, including the formation of blastemas and even new heads. Jochen Rink and colleagues show that in the otherwise regeneration-incompetent Dendrocoelum lacteum, knockdown of components in the Wnt signalling pathway introduces the ability to regenerate lost tissues. Variability of regenerative potential among animals has long perplexed biologists1. On the basis of their exceptional regenerative abilities, Planarians have become important models for understanding the molecular basis of regeneration2. However, Planarian species with limited regenerative abilities are also found3,4. Despite the importance of understanding the differences between closely related, regenerating and non-regenerating organisms, few studies have focused on the evolutionary loss of regeneration5, and the molecular mechanisms leading to such regenerative loss remain obscure. Here we examine Procotyla fluviatilis, a Planarian with restricted ability to replace missing tissues6, using next-generation sequencing to define the gene expression programs active in regeneration-permissive and regeneration-deficient tissues. We found that Wnt signalling is aberrantly activated in regeneration-deficient tissues. Notably, downregulation of canonical Wnt signalling in regeneration-deficient regions restores regenerative abilities: blastemas form and new heads regenerate in tissues that normally never regenerate. This work reveals that manipulating a single signalling pathway can reverse the evolutionary loss of regenerative potential.
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prmt5 and the role of symmetrical dimethylarginine in chromatoid bodies of Planarian stem cells
Development, 2012Co-Authors: Labib Rouhana, Ana P Vieira, Rachel H Robertsgalbraith, Phillip A. NewmarkAbstract:Planarian flatworms contain a population of adult stem cells (neoblasts) that proliferate and generate cells of all tissues during growth, regeneration and tissue homeostasis. A characteristic feature of neoblasts is the presence of chromatoid bodies, large cytoplasmic ribonucleoprotein (RNP) granules morphologically similar to structures present in the germline of many organisms. This study aims to reveal the function, and identify additional components, of Planarian chromatoid bodies. We uncover the presence of symmetrical dimethylarginine (sDMA) on chromatoid body components and identify the ortholog of protein arginine methyltransferase PRMT5 as the enzyme responsible for sDMA modification in these proteins. RNA interference-mediated depletion of Planarian PRMT5 results in defects in homeostasis and regeneration, reduced animal size, reduced number of neoblasts, fewer chromatoid bodies and increased levels of transposon and repetitive-element transcripts. Our results suggest that PIWI family member SMEDWI-3 is one sDMA-containing chromatoid body protein for which methylation depends on PRMT5. Additionally, we discover an RNA localized to chromatoid bodies, germinal histone H4. Our results reveal new components of chromatoid bodies and their function in Planarian stem cells, and also support emerging studies indicative of sDMA function in stabilization of RNP granules and the Piwi-interacting RNA pathway.
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the Planarian schmidtea mediterranea as a model for epigenetic germ cell specification analysis of ests from the hermaphroditic strain
Proceedings of the National Academy of Sciences of the United States of America, 2005Co-Authors: Ricardo M. Zayas, Alvaro G Hernandez, Bianca Habermann, Yuying Wang, Joel M Stary, Phillip A. NewmarkAbstract:Freshwater Planarians have prodigious regenerative abilities thatenable them to form complete organisms from tiny body frag-ments. This plasticity is also exhibited by the Planarian germ celllineage. Unlike many model organisms in which germ cells arespecified by localized determinants, Planarian germ cells appear tobe specified epigenetically, arising postembryonically from stemcells. The Planarian
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ingestion of bacterially expressed double stranded rna inhibits gene expression in Planarians
Proceedings of the National Academy of Sciences of the United States of America, 2003Co-Authors: Phillip A. Newmark, Francesc Cebrià, Peter W Reddien, Alejandro Sanchez AlvaradoAbstract:Freshwater Planarian flatworms are capable of regenerating complete organisms from tiny fragments of their bodies; the basis for this regenerative prowess is an experimentally accessible stem cell population that is present in the adult Planarian. The study of these organisms, classic experimental models for investigating metazoan regeneration, has been revitalized by the application of modern molecular biological approaches. The identification of thousands of unique Planarian ESTs, coupled with large-scale whole-mount in situ hybridization screens, and the ability to inhibit Planarian gene expression through double-stranded RNA-mediated genetic interference, provide a wealth of tools for studying the molecular mechanisms that regulate tissue regeneration and stem cell biology in these organisms. Here we show that, as in Caenorhabditis elegans, ingestion of bacterially expressed double-stranded RNA can inhibit gene expression in Planarians. This inhibition persists throughout the process of regeneration, allowing phenotypes with disrupted regenerative patterning to be identified. These results pave the way for large-scale screens for genes involved in regenerative processes.
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regeneration in Planaria
eLS, 2001Co-Authors: Phillip A. NewmarkAbstract:Inmetazoans,regenerationoflostbodypartsrequiringtheformationofablastemaisknownasepimorphicregenera-tion. A blastema is composed primarily of two cellpopulations:anoutercelllayerorectoderm,derivedfromtheepidermisthatcoversthewoundsurfaceafteramputa-tion/fission; andmesenchymal cells thatproliferate andaccumulate beneath this wound epidermis, eventuallydifferentiating into the lost body parts (
Katsuhiko Mineta - One of the best experts on this subject based on the ideXlab platform.
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structure and function of primitive immunoglobulin superfamily neural cell adhesion molecules a lesson from studies on Planarian
Genes to Cells, 2006Co-Authors: Eri Fusaoka, Takeshi Inoue, Katsuhiko Mineta, Kiyokazu Agata, Kosei TakeuchiAbstract:Precise wiring and proper remodeling of the neural network are essential for its normal function. The freshwater Planarian is an attractive animal in which to study the formation and maintenance of the neural network due to its high regenerative capability and developmental plasticity. Although a recent study revealed that homologs of netrin and its receptors are required for regeneration and maintenance of the Planarian central nervous system (CNS), the roles of cell adhesion in the formation and maintenance of the Planarian neural network remain poorly understood. In the present study, we found primitive immunoglobulin superfamily cell adhesion molecules (IgCAMs) in a Planarian that are homologous to vertebrate neural IgCAMs. We identified Planarian orthologs of NCAM, L1CAM, contactin and DSCAM, and designated them DjCAM, DjLCAM, DjCTCAM and DjDSCAM, respectively. We further confirmed that they function as cell adhesion molecules using cell aggregation assays. DjCAM and DjDSCAM were found to be differentially expressed in the CNS. Functional analyses using RNA interference revealed that DjCAM is partly involved in axon formation, and that DjDSCAM plays crucial roles in neuronal cell migration, axon outgrowth, fasciculation and projection.
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the expression of neural specific genes reveals the structural and molecular complexity of the Planarian central nervous system
Mechanisms of Development, 2002Co-Authors: Francesc Cebrià, Masumi Nakazawa, Katsuhiko Mineta, Kazuho Ikeo, Takashi Gojobori, Tomomi Kudome, Kiyokazu AgataAbstract:Planarians are attractive animals in which various questions related to the central nervous system (CNS) can be addressed, such as its origin and evolution, its degree of functional conservation among different organisms, and the plasticity and regenerative capabilities of neural cells and networks. However, it is first necessary to characterize at the gene expression level how this CNS is organized in intact animals. Previous studies have shown that the Planarian brain can be divided into at least three distinct domains based on the expression of otd/Otx-related genes. In order to further characterize the Planarian brain, we have recently isolated a large number of Planarian neural-specific genes through DNA microarrays and ESTs projects. Here, we describe new molecular domains within the brain of intact Planarians by the expression of 16 Planarian neural-specific genes, including the putative homologues of protein tyrosine phosphatase receptor, synaptotagmin VII, slit, G protein and glutamate and acetylcholine receptors, by in situ hybridization in both whole-mount and transverse sections. Our results indicate that Planarian otd/Otx-positive domains can be further subdivided into distinct molecular regions according to the expression of different neural genes. We found differences at the gene expression level between the dorsal and ventral sides of the brain, along its antero-posterior axis and also between the proximal and distal parts of the brain lateral branches. This high level of regionalization in the Planarian brain contrasts with its apparent simplicity at the morphological level.
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Dissecting Planarian central nervous system regeneration by the expression of neural-specific genes.
Development growth & differentiation, 2002Co-Authors: Francesc Cebrià, Masumi Nakazawa, Katsuhiko Mineta, Kazuho Ikeo, Takashi Gojobori, Kiyokazu AgataAbstract:The Planarian central nervous system (CNS) can be used as a model for studying neural regeneration in higher organisms. Despite its simple structure, recent studies have shown that the Planarian CNS can be divided into several molecular and functional domains defined by the expression of different neural genes. Remarkably, a whole animal, including the molecularly complex CNS, can regenerate from a small piece of the Planarian body. In this study, a collection of neural markers has been used to characterize at the molecular level how the Planarian CNS is rebuilt. Planarian CNS is composed of an anterior brain and a pair of ventral nerve cords that are distinct and overlapping structures in the head region. During regeneration, 12 neural markers have been classified as early, mid-regeneration and late expression genes depending on when they are upregulated in the regenerative blastema. Interestingly, the results from this study show that the comparison of the expression patterns of different neural genes supports the view that at day one of regeneration, the new brain appears within the blastema, whereas the pre-existing ventral nerve cords remain in the old tissues. Three stages in Planarian CNS regeneration are suggested.
Francesc Cebrià - One of the best experts on this subject based on the ideXlab platform.
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ingestion of bacterially expressed double stranded rna inhibits gene expression in Planarians
Proceedings of the National Academy of Sciences of the United States of America, 2003Co-Authors: Phillip A. Newmark, Francesc Cebrià, Peter W Reddien, Alejandro Sanchez AlvaradoAbstract:Freshwater Planarian flatworms are capable of regenerating complete organisms from tiny fragments of their bodies; the basis for this regenerative prowess is an experimentally accessible stem cell population that is present in the adult Planarian. The study of these organisms, classic experimental models for investigating metazoan regeneration, has been revitalized by the application of modern molecular biological approaches. The identification of thousands of unique Planarian ESTs, coupled with large-scale whole-mount in situ hybridization screens, and the ability to inhibit Planarian gene expression through double-stranded RNA-mediated genetic interference, provide a wealth of tools for studying the molecular mechanisms that regulate tissue regeneration and stem cell biology in these organisms. Here we show that, as in Caenorhabditis elegans, ingestion of bacterially expressed double-stranded RNA can inhibit gene expression in Planarians. This inhibition persists throughout the process of regeneration, allowing phenotypes with disrupted regenerative patterning to be identified. These results pave the way for large-scale screens for genes involved in regenerative processes.
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the expression of neural specific genes reveals the structural and molecular complexity of the Planarian central nervous system
Mechanisms of Development, 2002Co-Authors: Francesc Cebrià, Masumi Nakazawa, Katsuhiko Mineta, Kazuho Ikeo, Takashi Gojobori, Tomomi Kudome, Kiyokazu AgataAbstract:Planarians are attractive animals in which various questions related to the central nervous system (CNS) can be addressed, such as its origin and evolution, its degree of functional conservation among different organisms, and the plasticity and regenerative capabilities of neural cells and networks. However, it is first necessary to characterize at the gene expression level how this CNS is organized in intact animals. Previous studies have shown that the Planarian brain can be divided into at least three distinct domains based on the expression of otd/Otx-related genes. In order to further characterize the Planarian brain, we have recently isolated a large number of Planarian neural-specific genes through DNA microarrays and ESTs projects. Here, we describe new molecular domains within the brain of intact Planarians by the expression of 16 Planarian neural-specific genes, including the putative homologues of protein tyrosine phosphatase receptor, synaptotagmin VII, slit, G protein and glutamate and acetylcholine receptors, by in situ hybridization in both whole-mount and transverse sections. Our results indicate that Planarian otd/Otx-positive domains can be further subdivided into distinct molecular regions according to the expression of different neural genes. We found differences at the gene expression level between the dorsal and ventral sides of the brain, along its antero-posterior axis and also between the proximal and distal parts of the brain lateral branches. This high level of regionalization in the Planarian brain contrasts with its apparent simplicity at the morphological level.
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Dissecting Planarian central nervous system regeneration by the expression of neural-specific genes.
Development growth & differentiation, 2002Co-Authors: Francesc Cebrià, Masumi Nakazawa, Katsuhiko Mineta, Kazuho Ikeo, Takashi Gojobori, Kiyokazu AgataAbstract:The Planarian central nervous system (CNS) can be used as a model for studying neural regeneration in higher organisms. Despite its simple structure, recent studies have shown that the Planarian CNS can be divided into several molecular and functional domains defined by the expression of different neural genes. Remarkably, a whole animal, including the molecularly complex CNS, can regenerate from a small piece of the Planarian body. In this study, a collection of neural markers has been used to characterize at the molecular level how the Planarian CNS is rebuilt. Planarian CNS is composed of an anterior brain and a pair of ventral nerve cords that are distinct and overlapping structures in the head region. During regeneration, 12 neural markers have been classified as early, mid-regeneration and late expression genes depending on when they are upregulated in the regenerative blastema. Interestingly, the results from this study show that the comparison of the expression patterns of different neural genes supports the view that at day one of regeneration, the new brain appears within the blastema, whereas the pre-existing ventral nerve cords remain in the old tissues. Three stages in Planarian CNS regeneration are suggested.