The Experts below are selected from a list of 8079 Experts worldwide ranked by ideXlab platform
Kiyokazu Agata - One of the best experts on this subject based on the ideXlab platform.
-
MEK/ERK Signaling Regulates Reconstitution of the Dopaminergic Nerve Circuit in the Planarian Dugesia japonica
Neurochemical Research, 2021Co-Authors: Masanori Hijioka, Kiyokazu Agata, Takeshi Inoue, Kaneyasu Nishimura, Kazuyuki Takata, Yusuke Ikemoto, Kosuke Fukao, Tatsuki Kobayakawa, Yoshihisa KitamuraAbstract:Planarian Dugesia japonica is a flatworm that can autonomously regenerate its own body after an artificial amputation. A recent report showed the role of the mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK/ERK) pathway in the head morphogenesis during the Planarian regeneration process after amputation; however, neuron-specific regeneration mechanisms have not yet been reported. Here, whether MEK/ERK pathway was involved in the dopaminergic neuronal regeneration in Planarians was investigated. Planarians regenerated their body within 14 days after amputation; however, the head region morphogenesis was inhibited by MEK inhibitor U0126 (3 or 10 μM). Furthermore, the number of Planarian tyrosine hydroxylase (DjTH)-positive dopaminergic neurons in the regenerated head region was also decreased by U0126. The 6-hydroxydopamine (6-OHDA), a dopaminergic neurotoxin, can decrease the number of dopaminergic neurons; however, Planarians can regenerate dopaminergic neurons after injecting 6-OHDA into the intestinal tract. MEK inhibitor PD98059 (30 μM) or U0126 (10 μM) significantly decreased dopaminergic neurons 5 days after the 6-OHDA injection. During the regeneration process of dopaminergic neurons, phosphorylated histone H3 (H3P)-positive stem cells known as “neoblasts” were increased in the head region; however, MEK inhibitors significantly decreased the number of H3P-positive neoblasts. These results suggested that dopaminergic neuronal regeneration in Planarian was regulated by the MEK/ERK pathway.
-
RNA Interference in Planarians: Feeding and Injection of Synthetic dsRNA.
Methods in molecular biology (Clifton N.J.), 2018Co-Authors: Norito Shibata, Kiyokazu AgataAbstract:RNA interference (RNAi) is one of the simplest and easiest methods for specifically perturbing gene function in an organism. In Planarian research, RNAi is one of the essential methods for defining gene functions not only during regeneration, but also during other life history stages. Since the first report of the efficacy of RNAi in Planarians in 1999, several RNAi protocols have been reported. Here, we describe protocols to synthesize and deliver synthetic double-stranded RNA (dsRNA) to Planarians, either by injection or by feeding. Both are easy, effective, and economical means of investigating gene functions in Planarians.
-
Analyzing pERK Activation During Planarian Regeneration
Methods in molecular biology (Clifton N.J.), 2016Co-Authors: Susanna Fraguas, Yoshihiko Umesono, Kiyokazu Agata, Francesc CebriàAbstract:Planarians are an ideal model in which to study stem cell-based regeneration. After amputation, Planarian pluripotent stem cells surrounding the wound proliferate to produce the regenerative blastema, in which they differentiate into the missing tissues and structures. Recent independent studies in Planarians have shown that Smed-egfr-3, a gene encoding a homologue of epidermal growth factor (EGF) receptors, and DjerkA, which encodes an extracellular signal-regulated kinase (ERK), may control cell differentiation and blastema growth. However, because these studies were carried in two different Planarian species, the relationship between these two genes remains unclear. We have optimized anti-pERK immunostaining in Schmidtea mediterranea using the original protocol developed in Dugesia japonica. Both protocols are reported here as most laboratories worldwide work with one of these two species. Using this protocol we have determined that Smed-egfr-3 appears to be necessary for pERK activation during Planarian regeneration.
-
Spontaneous Behaviors and Wall-Curvature Lead to Apparent Wall Preference in Planarian.
PloS one, 2015Co-Authors: Yoshitaro Akiyama, Kiyokazu Agata, Takeshi InoueAbstract:The Planarian Dugesia japonica tends to stay near the walls of its breeding containers and experimental dishes in the laboratory, a phenomenon called “wall preference”. This behavior is thought to be important for environmental adaptation, such as hiding by Planarians in nature. However, the mechanisms regulating wall-preference behavior are not well understood, since this behavior occurs in the absence of any particular stimulation. Here we show the mechanisms of wall-preference behavior. Surprisingly, Planarian wall-preference behavior was also shown even by the head alone and by headless Planarians. These results indicate that Planarian “wall-preference” behavior only appears to be a “preference” behavior, and is actually an outcome of spontaneous behaviors, rather than of brain function. We found that in the absence of environmental cues Planarians moved basically straight ahead until they reached a wall, and that after reaching a wall, they changed their direction of movement to one tangential to the wall, suggesting that this spontaneous behavior may play a critical role in the wall preference. When we tested another spontaneous behavior, the wigwag movement of the Planarian head, using computer simulation with various wigwag angles and wigwag intervals, large wigwag angle and short wigwag interval reduced wall-preference behavior. This indicated that wigwag movement may determine the probability of staying near the wall or leaving the wall. Furthermore, in accord with this simulation, when we tested Planarian wall-preference behavior using several assay fields with different curvature of the wall, we found that concavity and sharp curvature of walls negatively impacted wall preference by affecting the permissible angle of the wigwag movement. Together, these results indicate that Planarian wall preference may be involuntarily caused by the combination of two spontaneous Planarian behaviors: moving straight ahead until reaching a wall and then moving along it in the absence of environmental cues, and wigwag movements of the head.
-
The molecular logic for Planarian regeneration along the anterior-posterior axis.
Nature, 2013Co-Authors: Yoshihiko Umesono, Junichi Tasaki, Yui Nishimura, Martina Hrouda, Eri Kawaguchi, Shigenobu Yazawa, Kazutaka Hosoda, Osamu Nishimura, Takeshi Inoue, Kiyokazu AgataAbstract:More than a century ago, Thomas Hunt Morgan attempted to explain the extraordinary regenerative ability of Planarians such as Dugesia japonica, which can regenerate a complete individual even from a tail fragment, by proposing that two opposing morphogenetic gradients along the anterior–posterior axis are required for regeneration; here ERK and β-catenin signalling are shown to form these gradients. 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. The Planarian Dugesia japonica can regenerate a complete individual from a head, trunk or tail fragment via activation of somatic pluripotent stem cells1,2. About a century ago, Thomas Hunt Morgan attempted to explain the extraordinary regenerative ability of Planarians by positing two opposing morphogenetic gradients of formative “head stuff” and “tail stuff” along the anterior–posterior axis3,4. However, Morgan’s hypothesis remains open to debate. Here we show that extracellular signal-related kinase (ERK) and Wnt/β-catenin signalling pathways establish a solid framework for Planarian regeneration. Our data suggest that ERK signalling forms a spatial gradient in the anterior region during regeneration. The fibroblast growth factor receptor-like gene nou-darake5 (which serves as an output of ERK signalling in the differentiating head) and posteriorly biased β-catenin activity6,7,8 negatively regulate ERK signalling along the anterior–posterior axis in distinct manners, and thereby posteriorize regenerating tissues outside the head region to reconstruct a complete head-to-tail axis. On the basis of this knowledge about D. japonica, we proposed that β-catenin signalling is responsible for the lack of head-regenerative ability of tail fragments in the Planarian Phagocata kawakatsui, and our confirmation thereof supports the notion that posterior β-catenin signalling negatively modulates the ERK signalling involved in anteriorization across Planarian species. These findings suggest that ERK signalling has a pivotal role in triggering globally dynamic differentiation of stem cells in a head-to-tail sequence through a default program that promotes head tissue specification in the absence of posteriorizing signals. Thus, we have confirmed the broad outline of Morgan’s hypothesis, and refined it on the basis of our proposed default property of Planarian stem cells.
Kerstin Bartscherer - One of the best experts on this subject based on the ideXlab platform.
-
The Planarian flatworm: an in vivo model for stem cell biology and nervous system regeneration.
Disease models & mechanisms, 2010Co-Authors: Luca Gentile, Francesc Cebrià, Kerstin BartschererAbstract:Planarian flatworms are an exception among bilaterians in that they possess a large pool of adult stem cells that enables them to promptly regenerate any part of their body, including the brain. Although known for two centuries for their remarkable regenerative capabilities, Planarians have only recently emerged as an attractive model for studying regeneration and stem cell biology. This revival is due in part to the availability of a sequenced genome and the development of new technologies, such as RNA interference and next-generation sequencing, which facilitate studies of Planarian regeneration at the molecular level. Here, we highlight why Planarians are an exciting tool in the study of regeneration and its underlying stem cell biology in vivo, and discuss the potential promises and current limitations of this model organism for stem cell research and regenerative medicine.
-
smed evi wntless is required for β catenin dependent and independent processes during Planarian regeneration
Development, 2009Co-Authors: Teresa Adell, Emili Saló, Michael Boutros, Kerstin BartschererAbstract:Planarians can regenerate a whole animal from only a small piece of their body, and have become an important model for stem cell biology. To identify regenerative processes dependent on Wnt growth factors in the Planarian Schmidtea mediterranea ( Smed ), we analyzed RNAi phenotypes of Evi, a transmembrane protein specifically required for the secretion of Wnt ligands. We show that, during regeneration, Smed-evi loss-of-function prevents posterior identity, leading to two-headed Planarians that resemble Smed -β -catenin1 RNAi animals. In addition, we observe regeneration defects of the nervous system that are not found after Smed -β -catenin1 RNAi. By systematic knockdown of all putative Smed Wnts in regenerating Planarians, we identify Smed-WntP-1 and Smed-Wnt11-2 as the putative posterior organizers, and demonstrate that Smed-Wnt5 is a regulator of neuronal organization and growth. Thus, our study provides evidence that Planarian Wnts are major regulators of regeneration, and that they signal through β-catenin-dependent and -independent pathways.
-
Smed-Evi/Wntless is required for β-catenin-dependent and -independent processes during Planarian regeneration
Development (Cambridge England), 2009Co-Authors: Teresa Adell, Emili Saló, Michael Boutros, Kerstin BartschererAbstract:Planarians can regenerate a whole animal from only a small piece of their body, and have become an important model for stem cell biology. To identify regenerative processes dependent on Wnt growth factors in the Planarian Schmidtea mediterranea ( Smed ), we analyzed RNAi phenotypes of Evi, a transmembrane protein specifically required for the secretion of Wnt ligands. We show that, during regeneration, Smed-evi loss-of-function prevents posterior identity, leading to two-headed Planarians that resemble Smed -β -catenin1 RNAi animals. In addition, we observe regeneration defects of the nervous system that are not found after Smed -β -catenin1 RNAi. By systematic knockdown of all putative Smed Wnts in regenerating Planarians, we identify Smed-WntP-1 and Smed-Wnt11-2 as the putative posterior organizers, and demonstrate that Smed-Wnt5 is a regulator of neuronal organization and growth. Thus, our study provides evidence that Planarian Wnts are major regulators of regeneration, and that they signal through β-catenin-dependent and -independent pathways.
Kannan Rangiah - One of the best experts on this subject based on the ideXlab platform.
-
A quantitative metabolomics peek into Planarian regeneration
The Analyst, 2015Co-Authors: Nivedita Natarajan, Padma Ramakrishnan, Dasaradhi Palakodeti, Viswanathan Lakshmanan, Kannan RangiahAbstract:The fresh water Planarian species Schmidtea mediterranea is an emerging stem cell model because of its capability to regenerate a whole animal from a small piece of tissue. It is one of the best model systems to address the basic mechanisms essential for regeneration. Here, we are interested in studying the roles of various amines, thiols and nucleotides in Planarian regeneration, stem cell function and growth. We developed mass spectrometry based quantitative methods and validated the differential enrichment of 35 amines, 7 thiol metabolites and 4 nucleotides from both intact and regenerating Planarians. Among the amines, alanine in sexual and asparagine in asexual are the highest (>1000 ng/mg) in the intact Planarians. The levels of thiols such as cysteine and GSH are 651 and 1107 ng mg(-1) in Planarians. Among the nucleotides, the level of cGMP is the lowest (0.03 ng mg(-1)) and the level of AMP is the highest (187 ng mg(-1)) in both of the Planarian strains. We also noticed increasing levels of amines in both anterior and posterior regenerating Planarians. The blastema from day 3 regenerating Planarians also showed higher amounts of many amines. Interestingly, the thiol (cysteine and GSH) levels are well maintained during Planarian regeneration. This suggests an inherent and effective mechanism to control induced oxidative stress because of the robust regeneration and stem cell proliferation. Like in intact Planarians, the level of cGMP is also very low in regenerating Planarians. Surprisingly, the levels of amines and thiols in head regenerating blastemas are ∼3 times higher compared to those for tail regenerating blastemas. Thus our results strongly indicate the potential roles of amines, thiols and nucleotides in Planarian regeneration.
-
comprehensive analysis of neurotransmitters from regenerating Planarian extract using an ultrahigh performance liquid chromatography mass spectrometry selected reaction monitoring method
Rapid Communications in Mass Spectrometry, 2013Co-Authors: Kannan Rangiah, Dasaradhi PalakodetiAbstract:RATIONALE Absolute quantification of neurotransmitters (NTs) from biological systems is imperative to track how changes in concentration of active neurochemicals may affect biological behavior. A sensitive method for the absolute quantification of multiple NTs in a single method is highly needed. METHODS A stable-isotope dilution ultrahigh-performance liquid chromatography/mass spectrometry/selected reaction monitoring (UHPLC/MS/SRM) assay has been developed for a sensitive and quantitative assessment of NTs in planaria. We used this method for the simultaneous quantification of 16 NTs. All analytes showed a linear relationship between concentrations (0.78–50 ng/mL), regression coefficients higher than 0.97, accuracy (91–109%) and low coefficients of variation (CVs). The inter-day CVs for the lowest quality controls (1.56 ng/mL) were in the range between 2–11%. RESULTS The levels of most of the NTs were similar in both sexual and asexual Planarians except for glutamic acid, which was about two-fold higher in asexual compared to sexual Planarians. We identified high levels of serotonin and failed to detect tryptamine suggesting that the pathway essential for the conversion of tryptophan into tryptamine is absent in Planarians. Interestingly, we also found high levels of dopamine and L-DOPA in regenerating Planarians suggesting their possible role in regeneration. CONCLUSIONS For the first time, we developed novel methodology based on UHPLC/MS/SRM and quantified 16 NTs with high sensitivity and specificity from sexual and asexual strains of Planarian Schmidtea mediterranea. This method will also have great application in quantifying various NTs with great precision in different model systems. Copyright © 2013 John Wiley & Sons, Ltd.
Phillip A. Newmark - One of the best experts on this subject based on the ideXlab platform.
-
gpcrs direct germline development and somatic gonad function in Planarians
PLOS Biology, 2016Co-Authors: Ami Saberi, Ayana Jamal, Isabel Eets, Liliane Schoofs, Phillip A. NewmarkAbstract:Planarians display remarkable plasticity in maintenance of their germline, with the ability to develop or dismantle reproductive tissues in response to systemic and environmental cues. Here, we investigated the role of G protein-coupled receptors (GPCRs) in this dynamic germline regulation. By genome-enabled receptor mining, we identified 566 putative Planarian GPCRs and classified them into conserved and phylum-specific subfamilies. We performed a functional screen to identify NPYR-1 as the cognate receptor for NPY-8, a neuropeptide required for sexual maturation and germ cell differentiation. Similar to NPY-8, knockdown of this receptor results in loss of differentiated germ cells and sexual maturity. NPYR-1 is expressed in neuroendocrine cells of the central nervous system and can be activated specifically by NPY-8 in cell-based assays. Additionally, we screened the complement of GPCRs with expression enriched in sexually reproducing Planarians, and identified an orphan chemoreceptor family member, ophis, that controls differentiation of germline stem cells (GSCs). ophis is expressed in somatic cells of male and female gonads, as well as in accessory reproductive tissues. We have previously shown that somatic gonadal cells are required for male GSC specification and maintenance in Planarians. However, ophis is not essential for GSC specification or maintenance and, therefore, defines a secondary role for Planarian gonadal niche cells in promoting GSC differentiation. Our studies uncover the complement of Planarian GPCRs and reveal previously unappreciated roles for these receptors in systemic and local (i.e., niche) regulation of germ cell development.
-
On the organ trail: insights into organ regeneration in the Planarian
Current opinion in genetics & development, 2015Co-Authors: Rachel H. Roberts-galbraith, Phillip A. NewmarkAbstract:Advances in stem cell biology have led to the derivation of diverse cell types, yet challenges remain in creating complex tissues and functional organs. Unlike humans, some animals regenerate all missing tissues and organs successfully after dramatic injuries. Studies of organisms with exceptional regenerative capacity, like Planarians, could complement in vitro studies and reveal mechanistic themes underlying regeneration on the scale of whole organs and tissues. In this review, we outline progress in understanding Planarian organ regeneration, with focus on recent studies of the nervous, digestive, and excretory systems. We further examine molecular mechanisms underlying establishment of diverse cell fates from the Planarian stem cell pool. Finally, we explore conceptual directions for future studies of organ regeneration in Planarians.
-
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.
-
follistatin antagonizes activin signaling and acts with notum to direct Planarian head regeneration
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: Rachel H Robertsgalbraith, Phillip A. NewmarkAbstract:Animals establish their body plans in embryogenesis, but only a few animals can recapitulate this signaling milieu for regeneration after injury. In Planarians, a pluripotent stem cell population and perpetual signaling of polarity axes collaborate to direct a steady replacement of cells during homeostasis and to power robust regeneration after even severe injuries. Several studies have documented the roles of conserved signaling pathways in maintaining and resetting axial polarity in Planarians, but it is unclear how Planarians reestablish polarity signaling centers after injury and whether these centers serve to influence identity decisions of stem cell progeny during their differentiation. Here we find that a Planarian Follistatin homolog directs regeneration of anterior identity by opposing an Activin/ActR-1/Smad2/3 signaling pathway. Follistatin and Notum, a Wnt inhibitor, are mutually required to reestablish an anterior signaling center that expresses both cues. Furthermore, we show that the direction of cells down particular differentiation paths requires regeneration of this anterior signaling center. Just as its amphibian counterpart in the organizer signals body plan and cell fate during embryogenesis, Planarian Follistatin promotes reestablishment of anterior polarity during regeneration and influences specification of cell types in the head and beyond.
-
The use of lectins as markers for differentiated secretory cells in Planarians.
Developmental dynamics : an official publication of the American Association of Anatomists, 2010Co-Authors: Ricardo M. Zayas, Francesc Cebrià, Tingxia Guo, Junjie Feng, Phillip A. NewmarkAbstract:Freshwater Planarians have reemerged as excellent models to investigate mechanisms underlying regeneration. The introduction of molecular tools has facilitated the study of Planarians, but cell- and tissue-specific markers are still needed to examine differentiation of most cell types. Here we report the utility of fluorescent lectin-conjugates to label tissues in the Planarian Schmidtea mediterranea. We show that 16 lectin-conjugates stain Planarian cells or tissues; 13 primarily label the secretory cells, their cytoplasmic projections, and terminal pores. Thus, we examined regeneration of the secretory system using lectin markers and functionally characterized two genes expressed in the secretory cells: marginal adhesive gland-1 (mag-1) and Smed-reticulocalbin1 (Smed-rcn1). RNAi knockdown of these genes caused a dramatic reduction of secretory cell lectin staining, suggesting a role for mag-1 and Smed-rcn1 in secretory cell differentiation. Our results provide new insights into Planarian secretory system regeneration and add new markers for labeling several Planarian tissues. Developmental Dynamics 239:2888–2897, 2010. © 2010 Wiley-Liss, Inc.
Francesc Cebrià - One of the best experts on this subject based on the ideXlab platform.
-
Analyzing pERK Activation During Planarian Regeneration
Methods in molecular biology (Clifton N.J.), 2016Co-Authors: Susanna Fraguas, Yoshihiko Umesono, Kiyokazu Agata, Francesc CebriàAbstract:Planarians are an ideal model in which to study stem cell-based regeneration. After amputation, Planarian pluripotent stem cells surrounding the wound proliferate to produce the regenerative blastema, in which they differentiate into the missing tissues and structures. Recent independent studies in Planarians have shown that Smed-egfr-3, a gene encoding a homologue of epidermal growth factor (EGF) receptors, and DjerkA, which encodes an extracellular signal-regulated kinase (ERK), may control cell differentiation and blastema growth. However, because these studies were carried in two different Planarian species, the relationship between these two genes remains unclear. We have optimized anti-pERK immunostaining in Schmidtea mediterranea using the original protocol developed in Dugesia japonica. Both protocols are reported here as most laboratories worldwide work with one of these two species. Using this protocol we have determined that Smed-egfr-3 appears to be necessary for pERK activation during Planarian regeneration.
-
The Planarian flatworm: an in vivo model for stem cell biology and nervous system regeneration.
Disease models & mechanisms, 2010Co-Authors: Luca Gentile, Francesc Cebrià, Kerstin BartschererAbstract:Planarian flatworms are an exception among bilaterians in that they possess a large pool of adult stem cells that enables them to promptly regenerate any part of their body, including the brain. Although known for two centuries for their remarkable regenerative capabilities, Planarians have only recently emerged as an attractive model for studying regeneration and stem cell biology. This revival is due in part to the availability of a sequenced genome and the development of new technologies, such as RNA interference and next-generation sequencing, which facilitate studies of Planarian regeneration at the molecular level. Here, we highlight why Planarians are an exciting tool in the study of regeneration and its underlying stem cell biology in vivo, and discuss the potential promises and current limitations of this model organism for stem cell research and regenerative medicine.
-
The use of lectins as markers for differentiated secretory cells in Planarians.
Developmental dynamics : an official publication of the American Association of Anatomists, 2010Co-Authors: Ricardo M. Zayas, Francesc Cebrià, Tingxia Guo, Junjie Feng, Phillip A. NewmarkAbstract:Freshwater Planarians have reemerged as excellent models to investigate mechanisms underlying regeneration. The introduction of molecular tools has facilitated the study of Planarians, but cell- and tissue-specific markers are still needed to examine differentiation of most cell types. Here we report the utility of fluorescent lectin-conjugates to label tissues in the Planarian Schmidtea mediterranea. We show that 16 lectin-conjugates stain Planarian cells or tissues; 13 primarily label the secretory cells, their cytoplasmic projections, and terminal pores. Thus, we examined regeneration of the secretory system using lectin markers and functionally characterized two genes expressed in the secretory cells: marginal adhesive gland-1 (mag-1) and Smed-reticulocalbin1 (Smed-rcn1). RNAi knockdown of these genes caused a dramatic reduction of secretory cell lectin staining, suggesting a role for mag-1 and Smed-rcn1 in secretory cell differentiation. Our results provide new insights into Planarian secretory system regeneration and add new markers for labeling several Planarian tissues. Developmental Dynamics 239:2888–2897, 2010. © 2010 Wiley-Liss, Inc.
-
Regenerating the central nervous system: how easy for Planarians!
Development Genes and Evolution, 2007Co-Authors: Francesc CebriàAbstract:The regenerative capabilities of freshwater Planarians (Platyhelminthes) are very difficult to match. A fragment as tiny as 1/279th of the Planarian body is able to regenerate a whole animal within very few days [Morgan. Arch Entwm 7:364–397 (1898)]. Although the Planarian central nervous system (CNS) may appear quite morphologically simple, recent studies have shown it to be more complex at the molecular level, revealing a high degree of molecular compartmentalization in Planarian cephalic ganglia. Planarian neural genes include homologues of well-known transcription factors and genes involved in human diseases, neurotransmission, axon guidance, signaling pathways, and RNA metabolism. The availability of hundreds of genes expressed in Planarian neurons coupled with the ability to silence them through the use of RNA interference makes it possible to start unraveling the molecular mechanisms underlying CNS regeneration. In this review, I discuss current knowledge on the Planarian nervous system and the genes involved in its regeneration, and I discuss some of the important questions that remain to be answered.
-
regeneration and maintenance of the Planarian midline is regulated by a slit orthologue
Developmental Biology, 2007Co-Authors: Francesc Cebrià, Tingxia Guo, Jessica Jopek, Phillip A. NewmarkAbstract:Several families of evolutionarily conserved axon guidance cues orchestrate the precise wiring of the nervous system during embryonic development. The remarkable plasticity of freshwater Planarians provides the opportunity to study these molecules in the context of neural regeneration and maintenance. Here we characterize a homologue of the Slit family of guidance cues from the Planarian Schmidtea mediterranea. Smed-slit is expressed along the Planarian midline, in both dorsal and ventral domains. RNA interference (RNAi) targeting Smed-slit results in the collapse of many newly regenerated tissues at the midline; these include the cephalic ganglia, ventral nerve cords, photoreceptors, and the posterior digestive system. Surprisingly, Smed-slit RNAi knockdown animals also develop morphologically distinguishable, ectopic neural structures near the midline in uninjured regions of intact and regenerating Planarians. These results suggest that Smed-slit acts not only as a repulsive cue required for proper midline formation during regeneration but that it may also act to regulate the behavior of neural precursors at the midline in intact Planarians.
