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Akhlaghpour H. An RNA-Based Theory of Natural Universal Computation. J Theor Biol 2021; 537:110984. [PMID: 34979104 DOI: 10.1016/j.jtbi.2021.110984] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 09/30/2021] [Accepted: 12/07/2021] [Indexed: 12/15/2022]
Abstract
Life is confronted with computation problems in a variety of domains including animal behavior, single-cell behavior, and embryonic development. Yet we currently do not know of a naturally existing biological system that is capable of universal computation, i.e., Turing-equivalent in scope. Generic finite-dimensional dynamical systems (which encompass most models of neural networks, intracellular signaling cascades, and gene regulatory networks) fall short of universal computation, but are assumed to be capable of explaining cognition and development. I present a class of models that bridge two concepts from distant fields: combinatory logic (or, equivalently, lambda calculus) and RNA molecular biology. A set of basic RNA editing rules can make it possible to compute any computable function with identical algorithmic complexity to that of Turing machines. The models do not assume extraordinarily complex molecular machinery or any processes that radically differ from what we already know to occur in cells. Distinct independent enzymes can mediate each of the rules and RNA molecules solve the problem of parenthesis matching through their secondary structure. In the most plausible of these models all of the editing rules can be implemented with merely cleavage and ligation operations at fixed positions relative to predefined motifs. This demonstrates that universal computation is well within the reach of molecular biology. It is therefore reasonable to assume that life has evolved - or possibly began with - a universal computer that yet remains to be discovered. The variety of seemingly unrelated computational problems across many scales can potentially be solved using the same RNA-based computation system. Experimental validation of this theory may immensely impact our understanding of memory, cognition, development, disease, evolution, and the early stages of life.
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Affiliation(s)
- Hessameddin Akhlaghpour
- Laboratory of Integrative Brain Function, The Rockefeller University, New York, NY, 10065, USA
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2
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The Muller’s Ratchet and Aging. Trends Genet 2020; 36:395-402. [DOI: 10.1016/j.tig.2020.02.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 02/02/2020] [Accepted: 02/25/2020] [Indexed: 11/21/2022]
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Verheijen BM, Vermulst M, van Leeuwen FW. Somatic mutations in neurons during aging and neurodegeneration. Acta Neuropathol 2018; 135:811-826. [PMID: 29705908 PMCID: PMC5954077 DOI: 10.1007/s00401-018-1850-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Revised: 04/20/2018] [Accepted: 04/21/2018] [Indexed: 12/22/2022]
Abstract
The nervous system is composed of a large variety of neurons with a diverse array of morphological and functional properties. This heterogeneity is essential for the construction and maintenance of a distinct set of neural networks with unique characteristics. Accumulating evidence now indicates that neurons do not only differ at a functional level, but also at the genomic level. These genomic discrepancies seem to be the result of somatic mutations that emerge in nervous tissue during development and aging. Ultimately, these mutations bring about a genetically heterogeneous population of neurons, a phenomenon that is commonly referred to as "somatic brain mosaicism". Improved understanding of the development and consequences of somatic brain mosaicism is crucial to understand the impact of somatic mutations on neuronal function in human aging and disease. Here, we highlight a number of topics related to somatic brain mosaicism, including some early experimental evidence for somatic mutations in post-mitotic neurons of the hypothalamo-neurohypophyseal system. We propose that age-related somatic mutations are particularly interesting, because aging is a major risk factor for a variety of neuronal diseases, including Alzheimer's disease. We highlight potential links between somatic mutations and the development of these diseases and argue that recent advances in single-cell genomics and in vivo physiology have now finally made it possible to dissect the origins and consequences of neuronal mutations in unprecedented detail.
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Affiliation(s)
- Bert M Verheijen
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG, Utrecht, The Netherlands.
- Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3508 GA, Utrecht, The Netherlands.
| | - Marc Vermulst
- Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Fred W van Leeuwen
- Department of Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, 6229 ER, Maastricht, The Netherlands
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Picher ÁJ, Hernández F, Budeus B, Soriano E, Avila J. Human Brain Single Nucleotide Polymorphism: Validation of DNA Sequencing. J Alzheimers Dis Rep 2018; 2:103-109. [PMID: 30480253 PMCID: PMC6159612 DOI: 10.3233/adr-170039] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Genetic factors may be involved in the onset of neurodegenerative diseases like Alzheimer’s disease. In the case of the familial type, the disease is due to an inherited mutation at specific sites in three genes. Also, there are some genetic risk factors that facilitate the development of sporadic Alzheimer’s disease. All of these genetic analyses were performed using blood samples as a source of DNA. However, the presence of somatic mutations in the brain can be identified only using brain samples. In this review, we comment on a method that correctly identifies single nucleotide variations in the human brain and that can be used to validate high-through sequencing techniques. This method involves selective enrichment of the DNA population bearing the nucleotide variations, thereby facilitating posterior validation of the data by Sanger’s sequencing.
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Affiliation(s)
- Ángel J Picher
- Expedeon S.L.U., Parque Científico de Madrid, Cantoblanco, Madrid, Spain
| | - Félix Hernández
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), ISCIII, Madrid, Spain
| | | | - Eduardo Soriano
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), ISCIII, Madrid, Spain.,Department of Cell Biology and Institute of Neurosciences, University of Barcelona, Barcelona, Spain.,Vall d'Hebrón Institut de Recerca (VHIR), Barcelona, Spain.,ICREA Academia, Barcelona, Spain
| | - Jesús Avila
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), ISCIII, Madrid, Spain
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Larsen PA, Hunnicutt KE, Larsen RJ, Yoder AD, Saunders AM. Warning SINEs: Alu elements, evolution of the human brain, and the spectrum of neurological disease. Chromosome Res 2018; 26:93-111. [PMID: 29460123 PMCID: PMC5857278 DOI: 10.1007/s10577-018-9573-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 01/14/2018] [Accepted: 01/15/2018] [Indexed: 12/28/2022]
Abstract
Alu elements are a highly successful family of primate-specific retrotransposons that have fundamentally shaped primate evolution, including the evolution of our own species. Alus play critical roles in the formation of neurological networks and the epigenetic regulation of biochemical processes throughout the central nervous system (CNS), and thus are hypothesized to have contributed to the origin of human cognition. Despite the benefits that Alus provide, deleterious Alu activity is associated with a number of neurological and neurodegenerative disorders. In particular, neurological networks are potentially vulnerable to the epigenetic dysregulation of Alu elements operating across the suite of nuclear-encoded mitochondrial genes that are critical for both mitochondrial and CNS function. Here, we highlight the beneficial neurological aspects of Alu elements as well as their potential to cause disease by disrupting key cellular processes across the CNS. We identify at least 37 neurological and neurodegenerative disorders wherein deleterious Alu activity has been implicated as a contributing factor for the manifestation of disease, and for many of these disorders, this activity is operating on genes that are essential for proper mitochondrial function. We conclude that the epigenetic dysregulation of Alu elements can ultimately disrupt mitochondrial homeostasis within the CNS. This mechanism is a plausible source for the incipient neuronal stress that is consistently observed across a spectrum of sporadic neurological and neurodegenerative disorders.
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Affiliation(s)
- Peter A Larsen
- Department of Biology, Duke University, Durham, NC, 27708, USA.
- Duke Lemur Center, Duke University, Durham, NC, 27708, USA.
- Department of Biology, Duke University, 130 Science Drive, Box 90338, Durham, NC, 27708, USA.
| | | | - Roxanne J Larsen
- Duke University School of Medicine, Duke University, Durham, NC, 27710, USA
| | - Anne D Yoder
- Department of Biology, Duke University, Durham, NC, 27708, USA
- Duke Lemur Center, Duke University, Durham, NC, 27708, USA
| | - Ann M Saunders
- Zinfandel Pharmaceuticals Inc, Chapel Hill, NC, 27709, USA
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Loreto ELS, Pereira CM. Somatizing the transposons action. Mob Genet Elements 2017; 7:1-9. [PMID: 28580196 DOI: 10.1080/2159256x.2017.1314236] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 03/28/2017] [Accepted: 03/28/2017] [Indexed: 01/22/2023] Open
Abstract
The somatic mobilization of transposable elements is more common than previously thought. In this review we discuss how the intensity and the biologic consequences of somatic mobilization are dependent on the transposable elements landscapes of each genome, and on the "momentum" of each particular TE with respect to the mechanisms that control its transposition and the possibility to escape this control. Additionally, the biologic consequences of somatic mobilization vary among organisms that show an early separation between the germline and somatic cells and those organisms that do not exhibit this separation or that reproduce asexually. In the former, somatic transposition can be involved in phenotypic plasticity, detrimental conditions such as disease, or processes such as aging. For the organisms without separation between the germ and soma, somatic mobilization can be a source of genetic variability.
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Affiliation(s)
- Elgion L S Loreto
- Department of Biochemistry and Molecular Biology, University of Santa Maria, Santa Maria, RS, Brazil
| | - Camila Moura Pereira
- Postgraduate Programme in Animal Biodiversity, University of Santa Maria, Santa Maria, RS, Brazil
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Larsen PA, Lutz MW, Hunnicutt KE, Mihovilovic M, Saunders AM, Yoder AD, Roses AD. The Alu neurodegeneration hypothesis: A primate-specific mechanism for neuronal transcription noise, mitochondrial dysfunction, and manifestation of neurodegenerative disease. Alzheimers Dement 2017; 13:828-838. [PMID: 28242298 PMCID: PMC6647845 DOI: 10.1016/j.jalz.2017.01.017] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Revised: 01/12/2017] [Accepted: 01/24/2017] [Indexed: 01/13/2023]
Abstract
It is hypothesized that retrotransposons have played a fundamental role in primate evolution and that enhanced neurologic retrotransposon activity in humans may underlie the origin of higher cognitive function. As a potential consequence of this enhanced activity, it is likely that neurons are susceptible to deleterious retrotransposon pathways that can disrupt mitochondrial function. An example is observed in the TOMM40 gene, encoding a β-barrel protein critical for mitochondrial preprotein transport. Primate-specific Alu retrotransposons have repeatedly inserted into TOMM40 introns, and at least one variant associated with late-onset Alzheimer’s disease originated from an Alu insertion event. We provide evidence of enriched Alu content in mitochondrial genes and postulate that Alus can disrupt mitochondrial populations in neurons, thereby setting the stage for progressive neurologic dysfunction. This Alu neurodegeneration hypothesis is compatible with decades of research and offers a plausible mechanism for the disruption of neuronal mitochondrial homeostasis, ultimately cascading into neurodegenerative disease.
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Affiliation(s)
- Peter A Larsen
- Department of Biology, Duke University, Durham, NC, USA.
| | - Michael W Lutz
- Department of Neurology, Duke University School of Medicine, Durham, NC, USA
| | | | - Mirta Mihovilovic
- Department of Neurology, Duke University School of Medicine, Durham, NC, USA
| | - Ann M Saunders
- Department of Neurology, Duke University School of Medicine, Durham, NC, USA
| | - Anne D Yoder
- Department of Biology, Duke University, Durham, NC, USA; Duke Lemur Center, Duke University, Durham, NC, USA
| | - Allen D Roses
- Department of Neurology, Duke University School of Medicine, Durham, NC, USA; Zinfandel Pharmaceuticals, Inc, Durham, NC, USA
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