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Póti Á, Szüts D, Vermezovic J. Mutational profile of the regenerative process and de novo genome assembly of the planarian Schmidtea polychroa. Nucleic Acids Res 2024; 52:1779-1792. [PMID: 38180823 PMCID: PMC10899757 DOI: 10.1093/nar/gkad1250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 12/13/2023] [Accepted: 01/03/2024] [Indexed: 01/07/2024] Open
Abstract
Planarians are organisms with a unique capacity to regenerate any part of their body. New tissues are generated in a process that requires many swift cell divisions. How costly is this process to an animal in terms of mutational load remains unknown. Using whole genome sequencing, we defined the mutational profile of the process of regeneration in the planarian species Schmidtea polychroa. We assembled de novo the genome of S. polychroa and analyzed mutations in animals that have undergone regeneration. We observed a threefold increase in the number of mutations and an altered mutational spectrum. High allele frequencies of subclonal mutations in regenerated animals suggested that most of the cells in the regenerated animal were descendants of a small number of stem cells with high expansion potential. We provide, for the first time, the draft genome assembly of S. polychroa, an estimation of the germline mutation rate for a planarian species and the mutational spectrum of the regeneration process of a living organism.
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Affiliation(s)
- Ádám Póti
- Institute of Enzymology, Research Centre for Natural Sciences, Budapest, H-1117, Hungary
| | - Dávid Szüts
- Institute of Enzymology, Research Centre for Natural Sciences, Budapest, H-1117, Hungary
| | - Jelena Vermezovic
- IFOM ETS - The AIRC Institute of Molecular Oncology, Via Adamello 16, 20139 Milan, Italy
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2
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Metabolic cost of development, regeneration, and reproduction in the planarian Schmidtea mediterranea. Comp Biochem Physiol A Mol Integr Physiol 2021; 265:111127. [PMID: 34968657 DOI: 10.1016/j.cbpa.2021.111127] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2021] [Revised: 12/14/2021] [Accepted: 12/14/2021] [Indexed: 12/26/2022]
Abstract
Planaria are known for their ability to completely regenerate upon fissioning or experimental amputation. Yet, metabolic costs of regeneration have not been directly measured in planaria. Our goal was to establish the relationships between oxygen consumption (V̇O2), regeneration, and reproductive mode for asexual and sexual strains of Schmidtea mediterranea. We hypothesized that V̇O2 would vary by regeneration day for both sexual and asexual S. mediterranea, reflecting different costs of tissue reconstruction, but with an additional cost for regenerating sexual organs. Testes regeneration and body mass, as indicators of regeneration progress, and routine mass-specific V̇O2 as a function of maturity, regeneration, and reproductive mode, were measured over a 22-day regeneration period. Testes growth was highest in sexually mature adults, ~1/2 that in 14-day post-amputation sexual adults, and not detectable in juveniles and hatchlings. Mass-specific routine V̇O2 in sexuals was highest in mature controls at ~23 μl O2/g/h, but only half that in juveniles, hatchlings, and 14 day post-amputation adults. Both intact and 14-day post-amputation asexuals had a mass-specific routine V̇O2 of ~10-12 μl O2/g/h. The sum of V̇O2 of all amputated sections was ~100% higher than pre-amputation levels in the first 6 days of regeneration in asexuals, but not sexuals. There was no significant difference in V̇O2 of head, middle, and tail sections during regeneration. Overall, the highest metabolic costs associated with regeneration occurred during the initial 1-6 days of regeneration in both strains, but regeneration costs for sexual structures were not reflected in major V̇O2 differences between sexual and asexual strains.
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Abstract
The evolutionary theory of aging has set the foundations for a comprehensive understanding of aging. The biology of aging has listed and described the "hallmarks of aging," i.e., cellular and molecular mechanisms involved in human aging. The present paper is the first to infer the order of appearance of the hallmarks of bilaterian and thereby human aging throughout evolution from their presence in progressively narrower clades. Its first result is that all organisms, even non-senescent, have to deal with at least one mechanism of aging - the progressive accumulation of misfolded or unstable proteins. Due to their cumulation, these mechanisms are called "layers of aging." A difference should be made between the first four layers of unicellular aging, present in some unicellular organisms and in all multicellular opisthokonts, that stem and strike "from the inside" of individual cells and span from increasingly abnormal protein folding to deregulated nutrient sensing, and the last four layers of metacellular aging, progressively appearing in metazoans, that strike the cells of a multicellular organism "from the outside," i.e., because of other cells, and span from transcriptional alterations to the disruption of intercellular communication. The evolution of metazoans and eumetazoans probably solved the problem of aging along with the problem of unicellular aging. However, metacellular aging originates in the mechanisms by which the effects of unicellular aging are kept under control - e.g., the exhaustion of stem cells that contribute to replace damaged somatic cells. In bilaterians, additional functions have taken a toll on generally useless potentially limited lifespan to increase the fitness of organisms at the price of a progressively less efficient containment of the damage of unicellular aging. In the end, this picture suggests that geroscience should be more efficient in targeting conditions of metacellular aging rather than unicellular aging itself.
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Affiliation(s)
- Maël Lemoine
- CNRS, ImmunoConcEpT, UMR 5164, Univ. Bordeaux, Bordeaux, France
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4
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Lewallen M, Burggren W. Metabolic physiology of the freshwater planaria Girardia dorotocephela and Schmidtea mediterranea: reproductive mode, specific dynamic action, and temperature. Am J Physiol Regul Integr Comp Physiol 2020; 319:R428-R438. [PMID: 32783687 DOI: 10.1152/ajpregu.00099.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Planarians are widely used animal models for studies in regeneration, developmental biology, neurobiology, and behavior. However, surprisingly little is known about other aspects of their basic biology, even though such information might help validate these flatworms as a general animal model. We hypothesized that planaria, although dependent on simple diffusion of O2 across the integument for O2 uptake, would nonetheless show changes in oxygen consumption (V̇o2) associated with reproductive mode (sexual or asexual), feeding (specific dynamic action; SDA), temperature (Q10 values), and photoperiod typical of those responses of more complex invertebrates. In the current experiments, routine V̇o2 was measured over the range of 13-28°C in Schmidtea mediterranea and Girardia dorotocephala. At the long-term maintenance temperature of 18°C, routine V̇o2 was ~13 µL O2·g-1·h-1 in the two asexual strains, but approximately twice as high (27 µL O2·g-1·h-1) in the sexual strain of S. mediterranea, suggesting a metabolic cost for sexual reproduction. Metabolic temperature sensitivity, measured by Q10, was about one to three for all three groups. All three groups showed a large (~2- to 3-fold) increase in V̇o2 within a day following feeding, suggesting a large SDA effect. Starvation, causing "degrowth" in some planaria, resulted in a loss of one-third of body mass in sexual S. mediterranea but no body mass loss in either asexual strains. Collectively, these data indicate that, while being a relatively simple flatworm with no dedicated respiratory or circulatory system, their metabolic physiological responses are quite similar to those shown by more complex invertebrates and vertebrates, contributing to their validation as an animal model.
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Affiliation(s)
- Melissa Lewallen
- Developmental Integrative Biology, Department of Biological Sciences, University of North Texas, Denton, Texas
| | - Warren Burggren
- Developmental Integrative Biology, Department of Biological Sciences, University of North Texas, Denton, Texas
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Swapna LS, Molinaro AM, Lindsay-Mosher N, Pearson BJ, Parkinson J. Comparative transcriptomic analyses and single-cell RNA sequencing of the freshwater planarian Schmidtea mediterranea identify major cell types and pathway conservation. Genome Biol 2018; 19:124. [PMID: 30143032 PMCID: PMC6109357 DOI: 10.1186/s13059-018-1498-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 08/01/2018] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND In the Lophotrochozoa/Spiralia superphylum, few organisms have as high a capacity for rapid testing of gene function and single-cell transcriptomics as the freshwater planaria. The species Schmidtea mediterranea in particular has become a powerful model to use in studying adult stem cell biology and mechanisms of regeneration. Despite this, systematic attempts to define gene complements and their annotations are lacking, restricting comparative analyses that detail the conservation of biochemical pathways and identify lineage-specific innovations. RESULTS In this study we compare several transcriptomes and define a robust set of 35,232 transcripts. From this, we perform systematic functional annotations and undertake a genome-scale metabolic reconstruction for S. mediterranea. Cross-species comparisons of gene content identify conserved, lineage-specific, and expanded gene families, which may contribute to the regenerative properties of planarians. In particular, we find that the TRAF gene family has been greatly expanded in planarians. We further provide a single-cell RNA sequencing analysis of 2000 cells, revealing both known and novel cell types defined by unique signatures of gene expression. Among these are a novel mesenchymal cell population as well as a cell type involved in eye regeneration. Integration of our metabolic reconstruction further reveals the extent to which given cell types have adapted energy and nucleotide biosynthetic pathways to support their specialized roles. CONCLUSIONS In general, S. mediterranea displays a high level of gene and pathway conservation compared with other model systems, rendering it a viable model to study the roles of these pathways in stem cell biology and regeneration.
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Affiliation(s)
| | - Alyssa M Molinaro
- Hospital for Sick Children, Toronto, ON, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Nicole Lindsay-Mosher
- Hospital for Sick Children, Toronto, ON, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Bret J Pearson
- Hospital for Sick Children, Toronto, ON, Canada. .,Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada. .,Ontario Institute for Cancer Research, Toronto, ON, Canada.
| | - John Parkinson
- Hospital for Sick Children, Toronto, ON, Canada. .,Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada. .,Department of Biochemistry, University of Toronto, Toronto, ON, Canada.
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Felix DA, Gutiérrez-Gutiérrez Ó, Espada L, Thems A, González-Estévez C. It is not all about regeneration: Planarians striking power to stand starvation. Semin Cell Dev Biol 2018; 87:169-181. [PMID: 29705301 DOI: 10.1016/j.semcdb.2018.04.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Revised: 04/11/2018] [Accepted: 04/25/2018] [Indexed: 12/12/2022]
Abstract
All living forms, prokaryotes as eukaryotes, have some means of adaptation to food scarcity, which extends the survival chances under extreme environmental conditions. Nowadays we know that dietary interventions, including fasting, extends lifespan of many organisms and can also protect against age-related diseases including in humans. Therefore, the capacity of adapting to periods of food scarcity may have evolved billions of years ago not only to allow immediate organismal survival but also to be able to extend organismal lifespan or at least to lead to a healthier remaining lifespan. Planarians have been the center of attention since more than two centuries because of their astonishing power of full body regeneration that relies on a large amount of adult stem cells or neoblasts. However, they also present an often-overlooked characteristic. They are able to stand long time starvation. Planarians have adapted to periods of fasting by shrinking or degrowing. Here we will review the published data about starvation in planarians and conclude with the possibility of starvation being one of the processes that rejuvenate the planarian, thus explaining the historical notion of non-ageing planarians.
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Affiliation(s)
- Daniel A Felix
- Leibniz Institute on Aging - Fritz Lipmann Institute (FLI), Beutenbergstraße 11, 07745 Jena, Germany
| | - Óscar Gutiérrez-Gutiérrez
- Leibniz Institute on Aging - Fritz Lipmann Institute (FLI), Beutenbergstraße 11, 07745 Jena, Germany
| | - Lilia Espada
- Leibniz Institute on Aging - Fritz Lipmann Institute (FLI), Beutenbergstraße 11, 07745 Jena, Germany
| | - Anne Thems
- Leibniz Institute on Aging - Fritz Lipmann Institute (FLI), Beutenbergstraße 11, 07745 Jena, Germany
| | - Cristina González-Estévez
- Leibniz Institute on Aging - Fritz Lipmann Institute (FLI), Beutenbergstraße 11, 07745 Jena, Germany.
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7
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Rink JC. Stem Cells, Patterning and Regeneration in Planarians: Self-Organization at the Organismal Scale. Methods Mol Biol 2018; 1774:57-172. [PMID: 29916155 DOI: 10.1007/978-1-4939-7802-1_2] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The establishment of size and shape remains a fundamental challenge in biological research that planarian flatworms uniquely epitomize. Planarians can regenerate complete and perfectly proportioned animals from tiny and arbitrarily shaped tissue pieces; they continuously renew all organismal cell types from abundant pluripotent stem cells, yet maintain shape and anatomy in the face of constant turnover; they grow when feeding and literally degrow when starving, while scaling form and function over as much as a 40-fold range in body length or an 800-fold change in total cell numbers. This review provides a broad overview of the current understanding of the planarian stem cell system, the mechanisms that pattern the planarian body plan and how the interplay between patterning signals and cell fate choices orchestrates regeneration. What emerges is a conceptual framework for the maintenance and regeneration of the planarian body plan on basis of the interplay between pluripotent stem cells and self-organizing patterns and further, the general utility of planarians as model system for the mechanistic basis of size and shape.
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Affiliation(s)
- Jochen C Rink
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
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8
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Abstract
Planarians are on the rise as a model system for regeneration and stem cell dynamics. Almost in parallel the interest in planarian field biology has declined. Besides representing an independent research discipline in its own right, understanding of the natural habitat is also directly relevant to optimizing culture conditions in the laboratory. Moreover, the current laboratory models are but few of hundreds of planarian species worldwide. Their adaptation to a wide range of ecological niches has resulted in a fascinating diversity of regenerative abilities, body size, reproduction strategies, and life expectancy, to name just a few. With the currently ongoing establishment of large planarian species collections, such phenotypic diversity becomes accessible to comparative mechanistic analysis in the laboratory. Overall, we hope that this chapter inspires an integral view of the planarian model system that not only includes the molecular and cellular processes under investigation but also the evolutionary forces that shaped them in the first place.
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Affiliation(s)
- Miquel Vila-Farré
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Jochen C Rink
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
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9
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Brandl H, Moon H, Vila-Farré M, Liu SY, Henry I, Rink JC. PlanMine--a mineable resource of planarian biology and biodiversity. Nucleic Acids Res 2015; 44:D764-73. [PMID: 26578570 PMCID: PMC4702831 DOI: 10.1093/nar/gkv1148] [Citation(s) in RCA: 117] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Accepted: 10/19/2015] [Indexed: 11/13/2022] Open
Abstract
Planarian flatworms are in the midst of a renaissance as a model system for regeneration and stem cells. Besides two well-studied model species, hundreds of species exist worldwide that present a fascinating diversity of regenerative abilities, tissue turnover rates, reproductive strategies and other life history traits. PlanMine (http://planmine.mpi-cbg.de/) aims to accomplish two primary missions: First, to provide an easily accessible platform for sharing, comparing and value-added mining of planarian sequence data. Second, to catalyze the comparative analysis of the phenotypic diversity amongst planarian species. Currently, PlanMine houses transcriptomes independently assembled by our lab and community contributors. Detailed assembly/annotation statistics, a custom-developed BLAST viewer and easy export options enable comparisons at the contig and assembly level. Consistent annotation of all transcriptomes by an automated pipeline, the integration of published gene expression information and inter-relational query tools provide opportunities for mining planarian gene sequences and functions. For inter-species comparisons, we include transcriptomes of, so far, six planarian species, along with images, expert-curated information on their biology and pre-calculated cross-species sequence homologies. PlanMine is based on the popular InterMine system in order to make the rich biology of planarians accessible to the general life sciences research community.
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Affiliation(s)
- Holger Brandl
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - HongKee Moon
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Miquel Vila-Farré
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Shang-Yun Liu
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Ian Henry
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Jochen C Rink
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
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10
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Protein-borne methionine residues as structural antioxidants in mitochondria. Amino Acids 2015; 47:1421-32. [DOI: 10.1007/s00726-015-1955-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2014] [Accepted: 03/03/2015] [Indexed: 01/25/2023]
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11
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Laumer CE, Hejnol A, Giribet G. Nuclear genomic signals of the 'microturbellarian' roots of platyhelminth evolutionary innovation. eLife 2015; 4:e05503. [PMID: 25764302 PMCID: PMC4398949 DOI: 10.7554/elife.05503] [Citation(s) in RCA: 114] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 03/06/2015] [Indexed: 12/25/2022] Open
Abstract
Flatworms number among the most diverse invertebrate phyla and represent the most biomedically significant branch of the major bilaterian clade Spiralia, but to date, deep evolutionary relationships within this group have been studied using only a single locus (the rRNA operon), leaving the origins of many key clades unclear. In this study, using a survey of genomes and transcriptomes representing all free-living flatworm orders, we provide resolution of platyhelminth interrelationships based on hundreds of nuclear protein-coding genes, exploring phylogenetic signal through concatenation as well as recently developed consensus approaches. These analyses robustly support a modern hypothesis of flatworm phylogeny, one which emphasizes the primacy of the often-overlooked 'microturbellarian' groups in understanding the major evolutionary transitions within Platyhelminthes: perhaps most notably, we propose a novel scenario for the interrelationships between free-living and vertebrate-parasitic flatworms, providing new opportunities to shed light on the origins and biological consequences of parasitism in these iconic invertebrates.
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Affiliation(s)
- Christopher E Laumer
- Museum of Comparative Zoology, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States
| | - Andreas Hejnol
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Gonzalo Giribet
- Museum of Comparative Zoology, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States
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12
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Elliott KH, Hare JF, Le Vaillant M, Gaston AJ, Ropert‐Coudert Y, Anderson WG. Ageing gracefully: physiology but not behaviour declines with age in a diving seabird. Funct Ecol 2014. [DOI: 10.1111/1365-2435.12316] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kyle H. Elliott
- Department of Biological Sciences University of Manitoba Winnipeg Manitoba R3T 2N2 Canada
| | - James F. Hare
- Department of Biological Sciences University of Manitoba Winnipeg Manitoba R3T 2N2 Canada
| | - Maryline Le Vaillant
- IPHC Université de Strasbourg 23 rue Becquerel 67087 Strasbourg France
- Centre National de la Recherche Scientifiques UMR7178 67037 Strasbourg France
| | - Anthony J. Gaston
- National Wildlife Research Centre Environment Canada Carleton University Ottawa OntarioK1A 0H3 Canada
| | - Yan Ropert‐Coudert
- IPHC Université de Strasbourg 23 rue Becquerel 67087 Strasbourg France
- Centre National de la Recherche Scientifiques UMR7178 67037 Strasbourg France
| | - W. Gary Anderson
- Department of Biological Sciences University of Manitoba Winnipeg Manitoba R3T 2N2 Canada
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13
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Petralia RS, Mattson MP, Yao PJ. Aging and longevity in the simplest animals and the quest for immortality. Ageing Res Rev 2014; 16:66-82. [PMID: 24910306 DOI: 10.1016/j.arr.2014.05.003] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Revised: 05/08/2014] [Accepted: 05/22/2014] [Indexed: 12/12/2022]
Abstract
Here we review the examples of great longevity and potential immortality in the earliest animal types and contrast and compare these to humans and other higher animals. We start by discussing aging in single-celled organisms such as yeast and ciliates, and the idea of the immortal cell clone. Then we describe how these cell clones could become organized into colonies of different cell types that lead to multicellular animal life. We survey aging and longevity in all of the basal metazoan groups including ctenophores (comb jellies), sponges, placozoans, cnidarians (hydras, jellyfish, corals and sea anemones) and myxozoans. Then we move to the simplest bilaterian animals (with a head, three body cell layers, and bilateral symmetry), the two phyla of flatworms. A key determinant of longevity and immortality in most of these simple animals is the large numbers of pluripotent stem cells that underlie the remarkable abilities of these animals to regenerate and rejuvenate themselves. Finally, we discuss briefly the evolution of the higher bilaterians and how longevity was reduced and immortality lost due to attainment of greater body complexity and cell cycle strategies that protect these complex organisms from developing tumors. We also briefly consider how the evolution of multiple aging-related mechanisms/pathways hinders our ability to understand and modify the aging process in higher organisms.
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14
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Petralia RS, Mattson MP, Yao PJ. Communication breakdown: the impact of ageing on synapse structure. Ageing Res Rev 2014; 14:31-42. [PMID: 24495392 PMCID: PMC4094371 DOI: 10.1016/j.arr.2014.01.003] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2013] [Revised: 12/16/2013] [Accepted: 01/23/2014] [Indexed: 01/13/2023]
Abstract
Impaired synaptic plasticity is implicated in the functional decline of the nervous system associated with ageing. Understanding the structure of ageing synapses is essential to understanding the functions of these synapses and their role in the ageing nervous system. In this review, we summarize studies on ageing synapses in vertebrates and invertebrates, focusing on changes in morphology and ultrastructure. We cover different parts of the nervous system, including the brain, the retina, the cochlea, and the neuromuscular junction. The morphological characteristics of aged synapses could shed light on the underlying molecular changes and their functional consequences.
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Affiliation(s)
- Ronald S Petralia
- Advanced Imaging Core, NIDCD/NIH, Bethesda, MD 20892, United States.
| | - Mark P Mattson
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD 21224, United States
| | - Pamela J Yao
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD 21224, United States.
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15
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Abstract
Planarians are members of the Platyhelminthes (flatworms). These animals have evolved a remarkable stem cell system. A single pluripotent adult stem cell type ("neoblast") gives rise to the entire range of cell types and organs in the planarian body plan, including a brain, digestive-, excretory-, sensory- and reproductive systems. Neoblasts are abundantly present throughout the mesenchyme and divide continuously. The resulting stream of progenitors and turnover of differentiated cells drive the rapid self-renewal of the entire animal within a matter of weeks. Planarians grow and literally de-grow ("shrink") by the food supply-dependent adjustment of organismal turnover rates, scaling body plan proportions over as much as a 50-fold size range. Their dynamic body architecture further allows astonishing regenerative abilities, including the regeneration of complete and perfectly proportioned animals even from tiny tissue remnants. Planarians as an experimental system, therefore, provide unique opportunities for addressing a spectrum of current problems in stem cell research, including the evolutionary conservation of pluripotency, the dynamic organization of differentiation lineages and the mechanisms underlying organismal stem cell homeostasis. The first part of this review focuses on the molecular biology of neoblasts as pluripotent stem cells. The second part examines the fascinating mechanistic and conceptual challenges posed by a stem cell system that epitomizes a universal design principle of biological systems: the dynamic steady state.
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Affiliation(s)
- Jochen C Rink
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany.
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16
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The Fading Electricity Theory of Ageing: the missing biophysical principle? Ageing Res Rev 2013; 12:58-66. [PMID: 22940501 DOI: 10.1016/j.arr.2012.08.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Revised: 08/06/2012] [Accepted: 08/16/2012] [Indexed: 11/23/2022]
Abstract
Since a few years convincing data are accumulating showing that some of the premises of the master integrative theory of ageing, namely Harman's Reactive Oxygen Species or free radical theory, are less well founded than originally assumed. In addition, none of the about another dozen documented ageing mechanisms seems to hold the final answer as to the ultimate cause and evolutionary significance of ageing. This review raises the question whether, perhaps, something important has been overlooked, namely a biophysical principle, electrical in nature. The first cell on earth started to be alive when its system for generating its own electricity, carried by inorganic ions, became operational. Any cell dies at the very moment that this system irreversibly collapses. In between birth and death, the system is subject to wear and tear because any cell's overall repair system is not 100 percent waterproof; otherwise adaptation would not be an option. The Fading Electricity Theory of Ageing has all necessary properties for acting as a universal major integrative concept. The advent of novel methods will facilitate the study of bioelectrical phenomena with molecular biological methods in combination with optogenetics, thereby offering challenging possibilities for innovative research in evo-gero.
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