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Kozmik Z, Kozmikova I. Ancestral role of Pax6 in chordate brain regionalization. Front Cell Dev Biol 2024; 12:1431337. [PMID: 39119036 PMCID: PMC11306081 DOI: 10.3389/fcell.2024.1431337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2024] [Accepted: 07/10/2024] [Indexed: 08/10/2024] Open
Abstract
The Pax6 gene is essential for eye and brain development across various animal species. Here, we investigate the function of Pax6 in the development of the anterior central nervous system (CNS) of the invertebrate chordate amphioxus using CRISPR/Cas9-induced genome editing. Specifically, we examined Pax6 mutants featuring a 6 bp deletion encompassing two invariant amino acids in the conserved paired domain, hypothesized to impair Pax6 DNA-binding capacity and gene regulatory functions. Although this mutation did not result in gross morphological changes in amphioxus larvae, it demonstrated a reduced ability to activate Pax6-responsive reporter gene, suggesting a hypomorphic effect. Expression analysis in mutant larvae revealed changes in gene expression within the anterior CNS, supporting the conserved role of Pax6 gene in brain regionalization across chordates. Additionally, our findings lend support to the hypothesis of a zona limitans intrathalamica (ZLI)-like region in amphioxus, suggesting evolutionary continuity in brain patterning mechanisms. ZLI region, found in both hemichordates and vertebrates, functions as a key signaling center and serves as a restrictive boundary between major thalamic regions.
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Affiliation(s)
| | - Iryna Kozmikova
- Laboratory of Transcriptional Regulation, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czechia
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2
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Ordoñez JF, Wollesen T. Unfolding the ventral nerve center of chaetognaths. Neural Dev 2024; 19:5. [PMID: 38720353 PMCID: PMC11078758 DOI: 10.1186/s13064-024-00182-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 04/17/2024] [Indexed: 05/12/2024] Open
Abstract
BACKGROUND Chaetognaths are a clade of marine worm-like invertebrates with a heavily debated phylogenetic position. Their nervous system superficially resembles the protostome type, however, knowledge regarding the molecular processes involved in neurogenesis is lacking. To better understand these processes, we examined the expression profiles of marker genes involved in bilaterian neurogenesis during post-embryonic stages of Spadella cephaloptera. We also investigated whether the transcription factor encoding genes involved in neural patterning are regionally expressed in a staggered fashion along the mediolateral axis of the nerve cord as it has been previously demonstrated in selected vertebrate, insect, and annelid models. METHODS The expression patterns of genes involved in neural differentiation (elav), neural patterning (foxA, nkx2.2, pax6, pax3/7, and msx), and neuronal function (ChAT and VAChT) were examined in S. cephaloptera hatchlings and early juveniles using whole-mount fluorescent in situ hybridization and confocal microscopy. RESULTS The Sce-elav + profile of S. cephaloptera hatchlings reveals that, within 24 h of post-embryonic development, the developing neural territories are not limited to the regions previously ascribed to the cerebral ganglion, the ventral nerve center (VNC), and the sensory organs, but also extend to previously unreported CNS domains that likely contribute to the ventral cephalic ganglia. In general, the neural patterning genes are expressed in distinct neural subpopulations of the cerebral ganglion and the VNC in hatchlings, eventually becoming broadly expressed with reduced intensity throughout the CNS in early juveniles. Neural patterning gene expression domains are also present outside the CNS, including the digestive tract and sensory organs. ChAT and VAChT domains within the CNS are predominantly observed in specific subpopulations of the VNC territory adjacent to the ventral longitudinal muscles in hatchlings. CONCLUSIONS The observed spatial expression domains of bilaterian neural marker gene homologs in S. cephaloptera suggest evolutionarily conserved roles in neurogenesis for these genes among bilaterians. Patterning genes expressed in distinct regions of the VNC do not show a staggered medial-to-lateral expression profile directly superimposable to other bilaterian models. Only when the VNC is conceptually laterally unfolded from the longitudinal muscle into a flat structure, an expression pattern bearing resemblance to the proposed conserved bilaterian mediolateral regionalization becomes noticeable. This finding supports the idea of an ancestral mediolateral patterning of the trunk nervous system in bilaterians.
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Affiliation(s)
- June F Ordoñez
- Unit for Integrative Zoology, Department of Evolutionary Biology, University of Vienna, 1030, Vienna, Austria
| | - Tim Wollesen
- Unit for Integrative Zoology, Department of Evolutionary Biology, University of Vienna, 1030, Vienna, Austria.
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Senovilla-Ganzo R, García-Moreno F. The Phylotypic Brain of Vertebrates, from Neural Tube Closure to Brain Diversification. BRAIN, BEHAVIOR AND EVOLUTION 2024; 99:45-68. [PMID: 38342091 DOI: 10.1159/000537748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 02/04/2024] [Indexed: 02/13/2024]
Abstract
BACKGROUND The phylotypic or intermediate stages are thought to be the most evolutionary conserved stages throughout embryonic development. The contrast with divergent early and later stages derived from the concept of the evo-devo hourglass model. Nonetheless, this developmental constraint has been studied as a whole embryo process, not at organ level. In this review, we explore brain development to assess the existence of an equivalent brain developmental hourglass. In the specific case of vertebrates, we propose to split the brain developmental stages into: (1) Early: Neurulation, when the neural tube arises after gastrulation. (2) Intermediate: Brain patterning and segmentation, when the neuromere identities are established. (3) Late: Neurogenesis and maturation, the stages when the neurons acquire their functionality. Moreover, we extend this analysis to other chordates brain development to unravel the evolutionary origin of this evo-devo constraint. SUMMARY Based on the existing literature, we hypothesise that a major conservation of the phylotypic brain might be due to the pleiotropy of the inductive regulatory networks, which are predominantly expressed at this stage. In turn, earlier stages such as neurulation are rather mechanical processes, whose regulatory networks seem to adapt to environment or maternal geometries. The later stages are also controlled by inductive regulatory networks, but their effector genes are mostly tissue-specific and functional, allowing diverse developmental programs to generate current brain diversity. Nonetheless, all stages of the hourglass are highly interconnected: divergent neurulation must have a vertebrate shared end product to reproduce the vertebrate phylotypic brain, and the boundaries and transcription factor code established during the highly conserved patterning will set the bauplan for the specialised and diversified adult brain. KEY MESSAGES The vertebrate brain is conserved at phylotypic stages, but the highly conserved mechanisms that occur during these brain mid-development stages (Inducing Regulatory Networks) are also present during other stages. Oppositely, other processes as cell interactions and functional neuronal genes are more diverse and majoritarian in early and late stages of development, respectively. These phenomena create an hourglass of transcriptomic diversity during embryonic development and evolution, with a really conserved bottleneck that set the bauplan for the adult brain around the phylotypic stage.
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Affiliation(s)
- Rodrigo Senovilla-Ganzo
- Achucarro Basque Center for Neuroscience, Scientific Park of the University of the Basque Country (UPV/EHU), Leioa, Spain
- Department of Neuroscience, Faculty of Medicine and Odontology, UPV/EHU, Leioa, Spain
| | - Fernando García-Moreno
- Achucarro Basque Center for Neuroscience, Scientific Park of the University of the Basque Country (UPV/EHU), Leioa, Spain
- Department of Neuroscience, Faculty of Medicine and Odontology, UPV/EHU, Leioa, Spain
- IKERBASQUE Foundation, Bilbao, Spain
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4
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Cherry AL, Wheeler MJ, Mathisova K, Di Miceli M. In silico analyses of the involvement of GPR55, CB1R and TRPV1: response to THC, contribution to temporal lobe epilepsy, structural modeling and updated evolution. Front Neuroinform 2024; 18:1294939. [PMID: 38404644 PMCID: PMC10894036 DOI: 10.3389/fninf.2024.1294939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Accepted: 01/19/2024] [Indexed: 02/27/2024] Open
Abstract
Introduction The endocannabinoid (eCB) system is named after the discovery that endogenous cannabinoids bind to the same receptors as the phytochemical compounds found in Cannabis. While endogenous cannabinoids include anandamide (AEA) and 2-arachidonoylglycerol (2-AG), exogenous phytocannabinoids include Δ-9 tetrahydrocannabinol (THC) and cannabidiol (CBD). These compounds finely tune neurotransmission following synapse activation, via retrograde signaling that activates cannabinoid receptor 1 (CB1R) and/or transient receptor potential cation channel subfamily V member 1 (TRPV1). Recently, the eCB system has been linked to several neurological diseases, such as neuro-ocular abnormalities, pain insensitivity, migraine, epilepsy, addiction and neurodevelopmental disorders. In the current study, we aim to: (i) highlight a potential link between the eCB system and neurological disorders, (ii) assess if THC exposure alters the expression of eCB-related genes, and (iii) identify evolutionary-conserved residues in CB1R or TRPV1 in light of their function. Methods To address this, we used several bioinformatic approaches, such as transcriptomic (Gene Expression Omnibus), protein-protein (STRING), phylogenic (BLASTP, MEGA) and structural (Phyre2, AutoDock, Vina, PyMol) analyzes. Results Using RNA sequencing datasets, we did not observe any dysregulation of eCB-related transcripts in major depressive disorders, bipolar disorder or schizophrenia in the anterior cingulate cortex, nucleus accumbens or dorsolateral striatum. Following in vivo THC exposure in adolescent mice, GPR55 was significantly upregulated in neurons from the ventral tegmental area, while other transcripts involved in the eCB system were not affected by THC exposure. Our results also suggest that THC likely induces neuroinflammation following in vitro application on mice microglia. Significant downregulation of TPRV1 occurred in the hippocampi of mice in which a model of temporal lobe epilepsy was induced, confirming previous observations. In addition, several transcriptomic dysregulations were observed in neurons of both epileptic mice and humans, which included transcripts involved in neuronal death. When scanning known interactions for transcripts involved in the eCB system (n = 12), we observed branching between the eCB system and neurophysiology, including proteins involved in the dopaminergic system. Our protein phylogenic analyzes revealed that CB1R forms a clade with CB2R, which is distinct from related paralogues such as sphingosine-1-phosphate, receptors, lysophosphatidic acid receptors and melanocortin receptors. As expected, several conserved residues were identified, which are crucial for CB1R receptor function. The anandamide-binding pocket seems to have appeared later in evolution. Similar results were observed for TRPV1, with conserved residues involved in receptor activation. Conclusion The current study found that GPR55 is upregulated in neurons following THC exposure, while TRPV1 is downregulated in temporal lobe epilepsy. Caution is advised when interpreting the present results, as we have employed secondary analyzes. Common ancestors for CB1R and TRPV1 diverged from jawless vertebrates during the late Ordovician, 450 million years ago. Conserved residues are identified, which mediate crucial receptor functions.
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Affiliation(s)
- Amy L. Cherry
- Worcester Biomedical Research Group, School of Science and the Environment, University of Worcester, Worcester, United Kingdom
| | - Michael J. Wheeler
- Sustainable Environments Research Group, School of Science and the Environment University of Worcester, Worcester, United Kingdom
| | - Karolina Mathisova
- School of Science and the Environment University of Worcester, Worcester, United Kingdom
| | - Mathieu Di Miceli
- Worcester Biomedical Research Group, School of Science and the Environment, University of Worcester, Worcester, United Kingdom
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Lacalli T. The Cambrian fossil Pikaia, and the origin of chordate somites. EvoDevo 2024; 15:1. [PMID: 38302988 PMCID: PMC10832150 DOI: 10.1186/s13227-024-00222-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Accepted: 01/17/2024] [Indexed: 02/03/2024] Open
Abstract
The Middle Cambrian fossil Pikaia has a regular series of vertical bands that, assuming chordate affinities, can be interpreted as septa positioned between serial myotomes. Whether Pikaia has a notochord and nerve cord is less certain, as the dorsal organ, which has no obvious counterpart in living chordates, is the only clearly defined axial structure extending the length of the body. Without a notochord to serve as a reference point, the location of the nerve cord is then conjectural, which begs the question of how a dorsal neural center devoted to somite innervation would first have arisen from a more diffuse ancestral plexus of intraepithelial nerves. This question is examined using hemichordates as a reference point, first for the information they provide on the organization of the ancestral deuterostome nervous system, and second, extending the analysis of E. E. Ruppert, to explain why neural infoldings like the enteropneust collar cord would first have evolved. Both implicate the medial surface of the anterior-most part of the metacoel as the likely site for the evolution of the first somites. The analysis highlights the importance of the somatobranchial condition in chordates, meaning the linkage between the anterior trunk, hox1 expression, and the beginning of the gill series and somites. This feature is arguably a valid criterion by which to assess extinct taxa from the Cambrian that resemble chordates (e.g., vetulicolians and yunnanozoans), but may be unrelated to them. In a more speculative vein, the nature of the dorsal organ is discussed, including the possibility that it is an expanded neural tube combining neural and support functions in one structure.
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Affiliation(s)
- Thurston Lacalli
- Biology Department, University of Victoria, Victoria, V8W-3N5, Canada.
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Gilbert E, Craggs J, Modepalli V. Gene Regulatory Network that Shaped the Evolution of Larval Apical Organ in Cnidaria. Mol Biol Evol 2024; 41:msad285. [PMID: 38152864 PMCID: PMC10781443 DOI: 10.1093/molbev/msad285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 11/24/2023] [Accepted: 12/21/2023] [Indexed: 12/29/2023] Open
Abstract
Among non-bilaterian animals, a larval apical sensory organ with integrated neurons is only found in cnidarians. Within cnidarians, an apical organ with a ciliary tuft is mainly found in Actiniaria. Whether this apical tuft has evolved independently in Actiniaria or alternatively originated in the common ancestor of Cnidaria and Bilateria and was lost in specific groups is uncertain. To test this hypothesis, we generated transcriptomes of the apical domain during the planula stage of four species representing three key groups of cnidarians: Aurelia aurita (Scyphozoa), Nematostella vectensis (Actiniaria), and Acropora millepora and Acropora tenuis (Scleractinia). We showed that the canonical genes implicated in patterning the apical domain of N. vectensis are largely absent in A. aurita. In contrast, the apical domain of the scleractinian planula shares gene expression pattern with N. vectensis. By comparing the larval single-cell transcriptomes, we revealed the apical organ cell type of Scleractinia and confirmed its homology to Actiniaria. However, Fgfa2, a vital regulator of the regionalization of the N. vectensis apical organ, is absent in the scleractinian genome. Likewise, we found that FoxJ1 and 245 genes associated with cilia are exclusively expressed in the N. vectensis apical domain, which is in line with the presence of ciliary apical tuft in Actiniaria and its absence in Scleractinia and Scyphozoa. Our findings suggest that the common ancestor of cnidarians lacked a ciliary apical tuft, and it could have evolved independently in the Actiniaria.
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Affiliation(s)
- Eleanor Gilbert
- Marine Biological Association of the UK, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK
- School of Biological and Marine Sciences, University of Plymouth, Plymouth PL4 8AA, UK
| | - Jamie Craggs
- Horniman Museum and Gardens, London SE23 3PQ, UK
| | - Vengamanaidu Modepalli
- Marine Biological Association of the UK, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK
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Tremblay MÈ, Verkhratsky A. General Pathophysiology of Microglia. ADVANCES IN NEUROBIOLOGY 2024; 37:3-14. [PMID: 39207683 DOI: 10.1007/978-3-031-55529-9_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/04/2024]
Abstract
Microglia, which are the resident innate immune cells of the central nervous system (CNS), have emerged as critical for maintaining health by not only ensuring proper development, activity, and plasticity of neurones and glial cells but also maintaining and restoring homeostasis when faced with various challenges across the lifespan. This chapter is dedicated to the current understanding of microglia, including their beneficial versus detrimental roles, which are highly complex, rely on various microglial states, and intimately depend on their spatiotemporal context. Microglia are first contextualized within the perspective of finding therapeutic strategies to cure diseases in the twenty-first century-the overall functions of neuroglia with relation one to another and to neurones, and their shared CNS environment. A historical framework is provided, and the main principles of glial neuropathology are enunciated. The current view of microglial nomenclature is then covered, notably by discussing the rejected concepts of microglial activation, their polarisation into M1 and M2 phenotypes, and neuroinflammation. The transformation of the microglial population through the addition, migration, and elimination of individual members, as well as their dynamic metamorphosis between a wide variety of structural and functional states, based on the experienced physiological and pathological stimuli, is subsequently discussed. Lastly, the perspective of microglia as a cell type endowed with a health status determining their outcomes on adaptive CNS plasticity as well as disease pathology is proposed for twenty-first-century approaches to disease prevention and treatment.
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Affiliation(s)
- Marie-Ève Tremblay
- Division of Medical Sciences, Medical Sciences Building, University of Victoria, Victoria, BC, Canada.
- Axe neurosciences, Centre de recherche du CHU de Québec-Université Laval, Québec City, QC, Canada.
- Neurology and Neurosurgery Department, McGill University, Montreal, QC, Canada.
- Department of Molecular Medicine, Université Laval, Québec City, QC, Canada.
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Life Sciences Center, Vancouver, BC, Canada.
| | - Alexei Verkhratsky
- Faculty of Life Sciences, The University of Manchester, Manchester, UK.
- Department of Neurosciences,University of the Basque Country,, Leioa, Spain.
- Department of Stem Cell Biology, State Research Institute Centre for Innovative Medicine, Vilnius, Lithuania.
- Department of Forensic Analytical Toxicology, School of Forensic Medicine, China Medical University, Shenyang, China.
- IKERBASQUE, Basque Foundation for Science, Bilbao, Spain.
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8
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Kozol RA, Conith AJ, Yuiska A, Cree-Newman A, Tolentino B, Benesh K, Paz A, Lloyd E, Kowalko JE, Keene AC, Albertson C, Duboue ER. A brain-wide analysis maps structural evolution to distinct anatomical module. eLife 2023; 12:e80777. [PMID: 37498318 PMCID: PMC10435234 DOI: 10.7554/elife.80777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 07/26/2023] [Indexed: 07/28/2023] Open
Abstract
The vertebrate brain is highly conserved topologically, but less is known about neuroanatomical variation between individual brain regions. Neuroanatomical variation at the regional level is hypothesized to provide functional expansion, building upon ancestral anatomy needed for basic functions. Classically, animal models used to study evolution have lacked tools for detailed anatomical analysis that are widely used in zebrafish and mice, presenting a barrier to studying brain evolution at fine scales. In this study, we sought to investigate the evolution of brain anatomy using a single species of fish consisting of divergent surface and cave morphs, that permits functional genetic testing of regional volume and shape across the entire brain. We generated a high-resolution brain atlas for the blind Mexican cavefish Astyanax mexicanus and coupled the atlas with automated computational tools to directly assess variability in brain region shape and volume across all populations. We measured the volume and shape of every grossly defined neuroanatomical region of the brain and assessed correlations between anatomical regions in surface fish, cavefish, and surface × cave F2 hybrids, whose phenotypes span the range of surface to cave. We find that dorsal regions of the brain are contracted, while ventral regions have expanded, with F2 hybrid data providing support for developmental constraint along the dorsal-ventral axis. Furthermore, these dorsal-ventral relationships in anatomical variation show similar patterns for both volume and shape, suggesting that the anatomical evolution captured by these two parameters could be driven by similar developmental mechanisms. Together, these data demonstrate that A. mexicanus is a powerful system for functionally determining basic principles of brain evolution and will permit testing how genes influence early patterning events to drive brain-wide anatomical evolution.
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Affiliation(s)
- Robert A Kozol
- Jupiter Life Science Initiative, Florida Atlantic UniversityJupiterUnited States
| | - Andrew J Conith
- Department of Biology, University of Massachusetts AmherstAmherstUnited States
| | - Anders Yuiska
- Jupiter Life Science Initiative, Florida Atlantic UniversityJupiterUnited States
| | - Alexia Cree-Newman
- Jupiter Life Science Initiative, Florida Atlantic UniversityJupiterUnited States
| | - Bernadeth Tolentino
- Jupiter Life Science Initiative, Florida Atlantic UniversityJupiterUnited States
| | - Kasey Benesh
- Jupiter Life Science Initiative, Florida Atlantic UniversityJupiterUnited States
| | - Alexandra Paz
- Jupiter Life Science Initiative, Florida Atlantic UniversityJupiterUnited States
| | - Evan Lloyd
- Department of Biology, Texas A&M UniversityCollege StationUnited States
| | - Johanna E Kowalko
- Department of Biological Sciences, Lehigh UniversityBethlehemUnited States
| | - Alex C Keene
- Department of Biology, Texas A&M UniversityCollege StationUnited States
| | - Craig Albertson
- Department of Biology, University of Massachusetts AmherstAmherstUnited States
| | - Erik R Duboue
- Jupiter Life Science Initiative, Florida Atlantic UniversityJupiterUnited States
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Faltine-Gonzalez D, Havrilak J, Layden MJ. The brain regulatory program predates central nervous system evolution. Sci Rep 2023; 13:8626. [PMID: 37244953 DOI: 10.1038/s41598-023-35721-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Accepted: 05/23/2023] [Indexed: 05/29/2023] Open
Abstract
Understanding how brains evolved is critical to determine the origin(s) of centralized nervous systems. Brains are patterned along their anteroposterior axis by stripes of gene expression that appear to be conserved, suggesting brains are homologous. However, the striped expression is also part of the deeply conserved anteroposterior axial program. An emerging hypothesis is that similarities in brain patterning are convergent, arising through the repeated co-option of axial programs. To resolve whether shared brain neuronal programs likely reflect convergence or homology, we investigated the evolution of axial programs in neurogenesis. We show that the bilaterian anteroposterior program patterns the nerve net of the cnidarian Nematostella along the oral-aboral axis arguing that anteroposterior programs regionalized developing nervous systems in the cnidarian-bilaterian common ancestor prior to the emergence of brains. This finding rejects shared patterning as sufficient evidence to support brain homology and provides functional support for the plausibility that axial programs could be co-opted if nervous systems centralized in multiple lineages.
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Affiliation(s)
| | - Jamie Havrilak
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, USA
| | - Michael J Layden
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, USA.
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Adameyko I. Evolutionary origin of the neural tube in basal deuterostomes. Curr Biol 2023; 33:R319-R331. [PMID: 37098338 DOI: 10.1016/j.cub.2023.03.045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Abstract
The central nervous system (CNS) of chordates, including humans, develops as a hollow tube with ciliated walls containing cerebrospinal fluid. However, most of the animals inhabiting our planet do not use this design and rather build their centralized brains from non-epithelialized condensations of neurons called ganglia, with no traces of epithelialized tubes or liquid-containing cavities. The evolutionary origin of tube-type CNSs stays enigmatic, especially as non-epithelialized ganglionic-type nervous systems dominate the animal kingdom. Here, I discuss recent findings relevant to understanding the potential homologies and scenarios of the origin, histology and anatomy of the chordate neural tube. The nerve cords of other deuterostomes might relate to the chordate neural tube at histological, developmental and cellular levels, including the presence of radial glia, layered stratification, retained epithelial features, morphogenesis via folding and formation of a lumen filled with liquid. Recent findings inspire a new view of hypothetical evolutionary scenarios explaining the tubular epithelialized structure of the CNS. One such idea suggests that early neural tubes were key for improved directional olfaction, which was facilitated by the liquid-containing internal cavity. The later separation of the olfactory portion of the tube led to the formation of the independent olfactory and posterior tubular CNS systems in vertebrates. According to an alternative hypothesis, the thick basiepithelial nerve cords could provide deuterostome ancestors with additional biomechanical support, which later improved by turning the basiepithelial cord into a tube filled with liquid - a hydraulic skeleton.
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Affiliation(s)
- Igor Adameyko
- Center for Brain Research, Medical University of Vienna, Vienna, 1090, Austria; Department of Physiology and Pharmacology, Karolinska Institutet, Solna, 17165, Sweden.
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11
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Earl B. Humans, fish, spiders and bees inherited working memory and attention from their last common ancestor. Front Psychol 2023; 13:937712. [PMID: 36814887 PMCID: PMC9939904 DOI: 10.3389/fpsyg.2022.937712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 11/11/2022] [Indexed: 02/08/2023] Open
Abstract
All brain processes that generate behaviour, apart from reflexes, operate with information that is in an "activated" state. This activated information, which is known as working memory (WM), is generated by the effect of attentional processes on incoming information or information previously stored in short-term or long-term memory (STM or LTM). Information in WM tends to remain the focus of attention; and WM, attention and STM together enable information to be available to mental processes and the behaviours that follow on from them. WM and attention underpin all flexible mental processes, such as solving problems, making choices, preparing for opportunities or threats that could be nearby, or simply finding the way home. Neither WM nor attention are necessarily conscious, and both may have evolved long before consciousness. WM and attention, with similar properties, are possessed by humans, archerfish, and other vertebrates; jumping spiders, honey bees, and other arthropods; and members of other clades, whose last common ancestor (LCA) is believed to have lived more than 600 million years ago. It has been reported that very similar genes control the development of vertebrate and arthropod brains, and were likely inherited from their LCA. Genes that control brain development are conserved because brains generate adaptive behaviour. However, the neural processes that generate behaviour operate with the activated information in WM, so WM and attention must have existed prior to the evolution of brains. It is proposed that WM and attention are widespread amongst animal species because they are phylogenetically conserved mechanisms that are essential to all mental processing, and were inherited from the LCA of vertebrates, arthropods, and some other animal clades.
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12
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Nanglu K, Cole SR, Wright DF, Souto C. Worms and gills, plates and spines: the evolutionary origins and incredible disparity of deuterostomes revealed by fossils, genes, and development. Biol Rev Camb Philos Soc 2023; 98:316-351. [PMID: 36257784 DOI: 10.1111/brv.12908] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 09/23/2022] [Accepted: 09/28/2022] [Indexed: 01/12/2023]
Abstract
Deuterostomes are the major division of animal life which includes sea stars, acorn worms, and humans, among a wide variety of ecologically and morphologically disparate taxa. However, their early evolution is poorly understood, due in part to their disparity, which makes identifying commonalities difficult, as well as their relatively poor early fossil record. Here, we review the available morphological, palaeontological, developmental, and molecular data to establish a framework for exploring the origins of this important and enigmatic group. Recent fossil discoveries strongly support a vermiform ancestor to the group Hemichordata, and a fusiform active swimmer as ancestor to Chordata. The diverse and anatomically bewildering variety of forms among the early echinoderms show evidence of both bilateral and radial symmetry. We consider four characteristics most critical for understanding the form and function of the last common ancestor to Deuterostomia: Hox gene expression patterns, larval morphology, the capacity for biomineralization, and the morphology of the pharyngeal region. We posit a deuterostome last common ancestor with a similar antero-posterior gene regulatory system to that found in modern acorn worms and cephalochordates, a simple planktonic larval form, which was later elaborated in the ambulacrarian lineage, the ability to secrete calcium minerals in a limited fashion, and a pharyngeal respiratory region composed of simple pores. This animal was likely to be motile in adult form, as opposed to the sessile origins that have been historically suggested. Recent debates regarding deuterostome monophyly as well as the wide array of deuterostome-affiliated problematica further suggest the possibility that those features were not only present in the last common ancestor of Deuterostomia, but potentially in the ur-bilaterian. The morphology and development of the early deuterostomes, therefore, underpin some of the most significant questions in the study of metazoan evolution.
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Affiliation(s)
- Karma Nanglu
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
| | - Selina R Cole
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, 10th & Constitution Avenue NW, Washington, DC, 20560, USA.,Sam Noble Museum, University of Oklahoma, 2401 Chautauqua Avenue, Norman, OK, 73072, USA.,School of Geosciences, University of Oklahoma, 100 E Boyd Street, Norman, OK, 73019, USA
| | - David F Wright
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, 10th & Constitution Avenue NW, Washington, DC, 20560, USA.,Sam Noble Museum, University of Oklahoma, 2401 Chautauqua Avenue, Norman, OK, 73072, USA.,School of Geosciences, University of Oklahoma, 100 E Boyd Street, Norman, OK, 73019, USA
| | - Camilla Souto
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, 10th & Constitution Avenue NW, Washington, DC, 20560, USA.,School of Natural Sciences & Mathematics, Stockton University, 101 Vera King Farris Dr, Galloway, NJ, 08205, USA
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13
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Feuda R, Peter IS. Homologous gene regulatory networks control development of apical organs and brains in Bilateria. SCIENCE ADVANCES 2022; 8:eabo2416. [PMID: 36322649 PMCID: PMC9629743 DOI: 10.1126/sciadv.abo2416] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Apical organs are relatively simple larval nervous systems. The extent to which apical organs are evolutionarily related to the more complex nervous systems of other animals remains unclear. To identify common developmental mechanisms, we analyzed the gene regulatory network (GRN) controlling the development of the apical organ in sea urchins. We characterized the developmental expression of 30 transcription factors and identified key regulatory functions for FoxQ2, Hbn, Delta/Notch signaling, and SoxC in the patterning of the apical organ and the specification of neurons. Almost the entire set of apical transcription factors is expressed in the nervous system of worms, flies, zebrafish, frogs, and mice. Furthermore, a regulatory module controlling the axial patterning of the vertebrate brain is expressed in the ectoderm of sea urchin embryos. We conclude that GRNs controlling the formation of bilaterian nervous systems share a common origin and that the apical GRN likely resembles an ancestral regulatory program.
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14
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Leon A, Subirana L, Magre K, Cases I, Tena JJ, Irimia M, Gomez-Skarmeta JL, Escriva H, Bertrand S. Gene regulatory networks of epidermal and neural fate choice in a chordate. Mol Biol Evol 2022; 39:6547258. [PMID: 35276009 PMCID: PMC9004418 DOI: 10.1093/molbev/msac055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Neurons are a highly specialized cell type only found in metazoans. They can be scattered throughout the body or grouped together, forming ganglia or nerve cords. During embryogenesis, centralized nervous systems develop from the ectoderm, which also forms the epidermis. How pluripotent ectodermal cells are directed toward neural or epidermal fates, and to which extent this process is shared among different animal lineages, are still open questions. Here, by using micromere explants, we were able to define in silico the putative gene regulatory networks (GRNs) underlying the first steps of the epidermis and the central nervous system formation in the cephalochordate amphioxus. We propose that although the signal triggering neural induction in amphioxus (i.e., Nodal) is different from vertebrates, the main transcription factors implicated in this process are conserved. Moreover, our data reveal that transcription factors of the neural program seem to not only activate neural genes but also to potentially have direct inputs into the epidermal GRN, suggesting that the Nodal signal might also contribute to neural fate commitment by repressing the epidermal program. Our functional data on whole embryos support this result and highlight the complex interactions among the transcription factors activated by the signaling pathways that drive ectodermal cell fate choice in chordates.
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Affiliation(s)
- Anthony Leon
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins, BIOM, F-66650, Banyuls-sur-Mer, France
| | - Lucie Subirana
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins, BIOM, F-66650, Banyuls-sur-Mer, France
| | - Kevin Magre
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins, BIOM, F-66650, Banyuls-sur-Mer, France
| | - Ildefonso Cases
- Centro Andaluz de Biología del Desarrollo (CABD), CSIC-Universidad Pablo de Olavide-Junta de Andalucía, Sevilla, Spain
| | - Juan J Tena
- Centro Andaluz de Biología del Desarrollo (CABD), CSIC-Universidad Pablo de Olavide-Junta de Andalucía, Sevilla, Spain
| | - Manuel Irimia
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
| | - Jose Luis Gomez-Skarmeta
- Centro Andaluz de Biología del Desarrollo (CABD), CSIC-Universidad Pablo de Olavide-Junta de Andalucía, Sevilla, Spain
| | - Hector Escriva
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins, BIOM, F-66650, Banyuls-sur-Mer, France
| | - Stéphanie Bertrand
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins, BIOM, F-66650, Banyuls-sur-Mer, France
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15
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Mora A, Rakar J, Cobeta IM, Salmani BY, Starkenberg A, Thor S, Bodén M. Variational autoencoding of gene landscapes during mouse CNS development uncovers layered roles of Polycomb Repressor Complex 2. Nucleic Acids Res 2022; 50:1280-1296. [PMID: 35048973 PMCID: PMC8860581 DOI: 10.1093/nar/gkac006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 12/22/2021] [Accepted: 01/05/2022] [Indexed: 12/13/2022] Open
Abstract
A prominent aspect of most, if not all, central nervous systems (CNSs) is that anterior regions (brain) are larger than posterior ones (spinal cord). Studies in Drosophila and mouse have revealed that Polycomb Repressor Complex 2 (PRC2), a protein complex responsible for applying key repressive histone modifications, acts by several mechanisms to promote anterior CNS expansion. However, it is unclear what the full spectrum of PRC2 action is during embryonic CNS development and how PRC2 intersects with the epigenetic landscape. We removed PRC2 function from the developing mouse CNS, by mutating the key gene Eed, and generated spatio-temporal transcriptomic data. To decode the role of PRC2, we developed a method that incorporates standard statistical analyses with probabilistic deep learning to integrate the transcriptomic response to PRC2 inactivation with epigenetic data. This multi-variate analysis corroborates the central involvement of PRC2 in anterior CNS expansion, and also identifies several unanticipated cohorts of genes, such as proliferation and immune response genes. Furthermore, the analysis reveals specific profiles of regulation via PRC2 upon these gene cohorts. These findings uncover a differential logic for the role of PRC2 upon functionally distinct gene cohorts that drive CNS anterior expansion. To support the analysis of emerging multi-modal datasets, we provide a novel bioinformatics package that integrates transcriptomic and epigenetic datasets to identify regulatory underpinnings of heterogeneous biological processes.
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Affiliation(s)
- Ariane Mora
- School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, QLD 4072, Australia
| | - Jonathan Rakar
- Department of Clinical and Experimental Medicine, Linköping University, SE-58185 Linköping, Sweden
| | - Ignacio Monedero Cobeta
- Department of Clinical and Experimental Medicine, Linköping University, SE-58185 Linköping, Sweden
- Department of Physiology, Universidad Autonoma de Madrid, Madrid, Spain
| | - Behzad Yaghmaeian Salmani
- Department of Clinical and Experimental Medicine, Linköping University, SE-58185 Linköping, Sweden
- Department of Cell and Molecular Biology, Karolinska Institute, SE-171 65 Stockholm, Sweden
| | - Annika Starkenberg
- Department of Clinical and Experimental Medicine, Linköping University, SE-58185 Linköping, Sweden
| | - Stefan Thor
- Department of Clinical and Experimental Medicine, Linköping University, SE-58185 Linköping, Sweden
- School of Biomedical Sciences, University of Queensland, St Lucia, QLD 4072, Australia
| | - Mikael Bodén
- School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, QLD 4072, Australia
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16
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Lacalli T. An evolutionary perspective on chordate brain organization and function: insights from amphioxus, and the problem of sentience. Philos Trans R Soc Lond B Biol Sci 2022; 377:20200520. [PMID: 34957845 PMCID: PMC8710876 DOI: 10.1098/rstb.2020.0520] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The similarities between amphioxus and vertebrate brains, in their regional subdivision, cell types and circuitry, make the former a useful benchmark for understanding the evolutionary innovations that shaped the latter. Locomotory control systems were already well developed in basal chordates, with the ventral neuropile of the dien-mesencephalon serving to set levels of activity and initiate locomotory actions. A chief deficit in amphioxus is the absence of complex vertebrate-type sense organs. Hence, much of vertebrate story is one of progressive improvement both to these and to sensory experience more broadly. This has two aspects: (i) anatomical and neurocircuitry innovations in the organs of special sense and the brain centres that process and store their output, and (ii) the emergence of primary consciousness, i.e. sentience. With respect to the latter, a bottom up, evolutionary perspective has a different focus from a top down human-centric one. At issue: the obstacles to the emergence of sentience in the first instance, the sequence of addition of new contents to evolving consciousness, and the homology relationship between them. A further question, and a subject for future investigation, is how subjective experience is optimized for each sensory modality. This article is part of the theme issue 'Systems neuroscience through the lens of evolutionary theory'.
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Affiliation(s)
- Thurston Lacalli
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8 W-3N5
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17
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Furness JB. Comparative and Evolutionary Aspects of the Digestive System and Its Enteric Nervous System Control. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1383:165-177. [PMID: 36587156 DOI: 10.1007/978-3-031-05843-1_16] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
All life forms must gain nutrients from the environment and from single cell organisms to mammals a digestive system is present. Components of the digestive system that are recognized in mammals can be seen in the sea squirt that has had its current form for around 500my. Nevertheless, in mammals, the organ system that is most varied is the digestive system, its architecture being related to the dietary niche of each species. Forms include those of foregut or hindgut fermenters, single or multicompartment stomachs and short or capacious large intestines. Dietary niches include nectarivores, folivores, carnivores, etc. The human is exceptional in that, through food preparation (>80% of human consumption is prepared food in modern societies), humans can utilize a wider range of foods than other species. They are cucinivores, food preparers. In direct descendants of simple organisms, such as sponges, there is no ENS, but as the digestive tract becomes more complex, it requires integrated control of the movement and assimilation of its content. This is achieved by the nervous system, notably the enteric nervous system (ENS) and an array of gut hormones. An ENS is first observed in the phylum cnidaria, exemplified by hydra. But hydra has no collections of neurons that could in any way be regarded as a central nervous system. All animals more complex than hydra have an ENS, but not all have a CNS. In mammals, the ENS is extensive and is necessary for control of movement, enteric secretions and local blood flow, and regulation of the gut immune system. In animals with a CNS, the ENS and CNS have reciprocal connections. From hydra to human, an ENS is essential to life.
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Affiliation(s)
- John B Furness
- Digestive Physiology and Nutrition Laboratories, Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia.
- Department of Anatomy & Physiology, University of Melbourne, Parkville, VIC, Australia.
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18
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Abstract
We propose an expansion of neuroecological comparisons to include the capabilities of brainless and non-neural organisms. We begin this enterprise by conducting a systematic search for studies on learning in echinoderms. Echinodermata are marine invertebrates comprising starfish, brittle stars, sea cucumbers, sea urchins, and sea lilies. Animals in this phylum lack any centralized brain and instead possess diffuse neural networks known as nerve nets. The learning abilities of these animals are of particular interest as, within the bilaterian clade, they are close evolutionary neighbors to chordates, a phylum whose members exhibit complex feats in learning and contain highly specialized brains. The learning capacities and limitations of echinoderms can inform the evolution of nervous systems and learning in Bilateria. We find evidence of both non-associative and associative learning (in the form of classical conditioning) in echinoderms, which was primarily focused on starfish. Additional evidence of learning is documented in brittle stars, sand dollars, and sea urchins. We then discuss the evolutionary significance of learning capabilities without a brain, the presence of embodied cognition across multiple groups, and compare the learning present in echinoderms with the impressive cognitive abilities documented in the oldest linage group within vertebrates (the major group within the phylum of chordates), fish.
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19
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Fields C, Glazebrook JF, Levin M. Minimal physicalism as a scale-free substrate for cognition and consciousness. Neurosci Conscious 2021; 2021:niab013. [PMID: 34345441 PMCID: PMC8327199 DOI: 10.1093/nc/niab013] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 04/04/2021] [Accepted: 04/05/2021] [Indexed: 12/14/2022] Open
Abstract
Theories of consciousness and cognition that assume a neural substrate automatically regard phylogenetically basal, nonneural systems as nonconscious and noncognitive. Here, we advance a scale-free characterization of consciousness and cognition that regards basal systems, including synthetic constructs, as not only informative about the structure and function of experience in more complex systems but also as offering distinct advantages for experimental manipulation. Our "minimal physicalist" approach makes no assumptions beyond those of quantum information theory, and hence is applicable from the molecular scale upwards. We show that standard concepts including integrated information, state broadcasting via small-world networks, and hierarchical Bayesian inference emerge naturally in this setting, and that common phenomena including stigmergic memory, perceptual coarse-graining, and attention switching follow directly from the thermodynamic requirements of classical computation. We show that the self-representation that lies at the heart of human autonoetic awareness can be traced as far back as, and serves the same basic functions as, the stress response in bacteria and other basal systems.
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Affiliation(s)
- Chris Fields
- 23 Rue des Lavandières, 11160 Caunes Minervois, France
| | - James F Glazebrook
- Department of Mathematics and Computer Science, Eastern Illinois University, 600 Lincoln Ave, Charleston, IL 61920 USA
- Department of Mathematics, Adjunct Faculty, University of Illinois at Urbana–Champaign, 1409 W. Green Street, Urbana, IL 61801, USA
| | - Michael Levin
- Allen Discovery Center, Tufts University, 200 College Avenue, Medford, MA 02155, USA
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20
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Westwick RR, Rittschof CC. Insects Provide Unique Systems to Investigate How Early-Life Experience Alters the Brain and Behavior. Front Behav Neurosci 2021; 15:660464. [PMID: 33967715 PMCID: PMC8097038 DOI: 10.3389/fnbeh.2021.660464] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 03/16/2021] [Indexed: 12/24/2022] Open
Abstract
Early-life experiences have strong and long-lasting consequences for behavior in a surprising diversity of animals. Determining which environmental inputs cause behavioral change, how this information becomes neurobiologically encoded, and the functional consequences of these changes remain fundamental puzzles relevant to diverse fields from evolutionary biology to the health sciences. Here we explore how insects provide unique opportunities for comparative study of developmental behavioral plasticity. Insects have sophisticated behavior and cognitive abilities, and they are frequently studied in their natural environments, which provides an ecological and adaptive perspective that is often more limited in lab-based vertebrate models. A range of cues, from relatively simple cues like temperature to complex social information, influence insect behavior. This variety provides experimentally tractable opportunities to study diverse neural plasticity mechanisms. Insects also have a wide range of neurodevelopmental trajectories while sharing many developmental plasticity mechanisms with vertebrates. In addition, some insects retain only subsets of their juvenile neuronal population in adulthood, narrowing the targets for detailed study of cellular plasticity mechanisms. Insects and vertebrates share many of the same knowledge gaps pertaining to developmental behavioral plasticity. Combined with the extensive study of insect behavior under natural conditions and their experimental tractability, insect systems may be uniquely qualified to address some of the biggest unanswered questions in this field.
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Affiliation(s)
- Rebecca R Westwick
- Department of Entomology, University of Kentucky, Lexington, KY, United States
| | - Clare C Rittschof
- Department of Entomology, University of Kentucky, Lexington, KY, United States
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21
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Abstract
Many species from diverse and often distantly related animal groups (e.g. monkeys, crows, fish and bees) have a sense of number. This means that they can assess the number of items in a set - its 'numerosity'. The brains of these phylogenetically distant species are markedly diverse. This Review examines the fundamentally different types of brains and neural mechanisms that give rise to numerical competence across the animal tree of life. Neural correlates of the number sense so far exist only for specific vertebrate species: the richest data concerning explicit and abstract number representations have been collected from the cerebral cortex of mammals, most notably human and nonhuman primates, but also from the pallium of corvid songbirds, which evolved independently of the mammalian cortex. In contrast, the neural data relating to implicit and reflexive numerical representations in amphibians and fish is limited. The neural basis of a number sense has not been explored in any protostome so far. However, promising candidate regions in the brains of insects, spiders and cephalopods - all of which are known to have number skills - are identified in this Review. A comparative neuroscientific approach will be indispensable for identifying evolutionarily stable neuronal circuits and deciphering codes that give rise to a sense of number across phylogeny.
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Affiliation(s)
- Andreas Nieder
- Animal Physiology Unit, Institute of Neurobiology, University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
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22
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The emergence of the brain non-CpG methylation system in vertebrates. Nat Ecol Evol 2021; 5:369-378. [PMID: 33462491 PMCID: PMC7116863 DOI: 10.1038/s41559-020-01371-2] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 11/30/2020] [Indexed: 01/29/2023]
Abstract
Mammalian brains feature exceptionally high levels of non-CpG DNA methylation alongside the canonical form of CpG methylation. Non-CpG methylation plays a critical regulatory role in cognitive function, which is mediated by the binding of MeCP2, the transcriptional regulator that when mutated causes Rett syndrome. However, it is unclear whether the non-CpG neural methylation system is restricted to mammalian species with complex cognitive abilities or has deeper evolutionary origins. To test this, we investigated brain DNA methylation across 12 distantly related animal lineages, revealing that non-CpG methylation is restricted to vertebrates. We discovered that in vertebrates, non-CpG methylation is enriched within a highly conserved set of developmental genes transcriptionally repressed in adult brains, indicating that it demarcates a deeply conserved regulatory program. We also found that the writer of non-CpG methylation, DNMT3A, and the reader, MeCP2, originated at the onset of vertebrates as a result of the ancestral vertebrate whole-genome duplication. Together, we demonstrate how this novel layer of epigenetic information assembled at the root of vertebrates and gained new regulatory roles independent of the ancestral form of the canonical CpG methylation. This suggests that the emergence of non-CpG methylation may have fostered the evolution of sophisticated cognitive abilities found in the vertebrate lineage.
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23
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Abstract
Hemichordates, along with echinoderms and chordates, belong to the lineage of bilaterians called the deuterostomes. Their phylogenetic position as an outgroup to chordates provides an opportunity to investigate the evolutionary origins of the chordate body plan and reconstruct ancestral deuterostome characters. The body plans of the hemichordates and chordates are organizationally divergent making anatomical comparisons very challenging. The developmental underpinnings of animal body plans are often more conservative than the body plans they regulate, and offer a novel data set for making comparisons between morphologically divergent body architectures. Here I review the hemichordate developmental data generated over the past 20 years that further test hypotheses of proposed morphological affinities between the two taxa, but also compare the conserved anteroposterior, dorsoventral axial patterning programs and germ layer specification programs. These data provide an opportunity to determine which developmental programs are ancestral deuterostome or bilaterian innovations, and which ones occurred in stem chordates or vertebrates representing developmental novelties of the chordate body plan.
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24
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Barnes KM, Fan L, Moyle MW, Brittin CA, Xu Y, Colón-Ramos DA, Santella A, Bao Z. Cadherin preserves cohesion across involuting tissues during C. elegans neurulation. eLife 2020; 9:e58626. [PMID: 33030428 PMCID: PMC7544503 DOI: 10.7554/elife.58626] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 09/25/2020] [Indexed: 12/17/2022] Open
Abstract
The internalization of the central nervous system, termed neurulation in vertebrates, is a critical step in embryogenesis. Open questions remain regarding how force propels coordinated tissue movement during the process, and little is known as to how internalization happens in invertebrates. We show that in C. elegans morphogenesis, apical constriction in the retracting pharynx drives involution of the adjacent neuroectoderm. HMR-1/cadherin mediates this process via inter-tissue attachment, as well as cohesion within the neuroectoderm. Our results demonstrate that HMR-1 is capable of mediating embryo-wide reorganization driven by a centrally located force generator, and indicate a non-canonical use of cadherin on the basal side of an epithelium that may apply to vertebrate neurulation. Additionally, we highlight shared morphology and gene expression in tissues driving involution, which suggests that neuroectoderm involution in C. elegans is potentially homologous with vertebrate neurulation and thus may help elucidate the evolutionary origin of the brain.
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Affiliation(s)
- Kristopher M Barnes
- Developmental Biology Program, Memorial Sloan Kettering Cancer CenterNew YorkUnited States
- Graduate Program in Neuroscience, Weill Cornell MedicineNew YorkUnited States
| | - Li Fan
- Developmental Biology Program, Memorial Sloan Kettering Cancer CenterNew YorkUnited States
| | - Mark W Moyle
- Department of Neuroscience and Department of Cell Biology, Yale University School of MedicineNew HavenUnited States
| | - Christopher A Brittin
- Developmental Biology Program, Memorial Sloan Kettering Cancer CenterNew YorkUnited States
| | - Yichi Xu
- Developmental Biology Program, Memorial Sloan Kettering Cancer CenterNew YorkUnited States
| | - Daniel A Colón-Ramos
- Department of Neuroscience and Department of Cell Biology, Yale University School of MedicineNew HavenUnited States
- Instituto de Neurobiología, Recinto de Ciencias Médicas, Universidad de Puerto RicoSan JuanUnited States
| | - Anthony Santella
- Developmental Biology Program, Memorial Sloan Kettering Cancer CenterNew YorkUnited States
- Molecular Cytology Core, Memorial Sloan Kettering Cancer CenterNew YorkUnited States
| | - Zhirong Bao
- Developmental Biology Program, Memorial Sloan Kettering Cancer CenterNew YorkUnited States
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25
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Kumar S, Tumu SC, Helm C, Hausen H. The development of early pioneer neurons in the annelid Malacoceros fuliginosus. BMC Evol Biol 2020; 20:117. [PMID: 32928118 PMCID: PMC7489019 DOI: 10.1186/s12862-020-01680-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 08/27/2020] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Nervous system development is an interplay of many processes: the formation of individual neurons, which depends on whole-body and local patterning processes, and the coordinated growth of neurites and synapse formation. While knowledge of neural patterning in several animal groups is increasing, data on pioneer neurons that create the early axonal scaffold are scarce. Here we studied the first steps of nervous system development in the annelid Malacoceros fuliginosus. RESULTS We performed a dense expression profiling of a broad set of neural genes. We found that SoxB expression begins at 4 h postfertilization, and shortly later, the neuronal progenitors can be identified at the anterior and the posterior pole by the transient and dynamic expression of proneural genes. At 9 hpf, the first neuronal cells start differentiating, and we provide a detailed description of axonal outgrowth of the pioneer neurons that create the primary neuronal scaffold. Tracing back the clonal origin of the ventral nerve cord pioneer neuron revealed that it is a descendant of the blastomere 2d (2d221), which after 7 cleavages starts expressing Neurogenin, Acheate-Scute and NeuroD. CONCLUSIONS We propose that an anterior and posterior origin of the nervous system is ancestral in annelids. We suggest that closer examination of the first pioneer neurons will be valuable in better understanding of nervous system development in spirally cleaving animals, to determine the potential role of cell-intrinsic properties in neuronal specification and to resolve the evolution of nervous systems.
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Affiliation(s)
- Suman Kumar
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Sharat Chandra Tumu
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Conrad Helm
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway.,Present Address: Johann-Friedrich-Blumenbach Institute for Zoology and Anthropology, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Harald Hausen
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway.
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26
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Ancestral regulatory mechanisms specify conserved midbrain circuitry in arthropods and vertebrates. Proc Natl Acad Sci U S A 2020; 117:19544-19555. [PMID: 32747566 PMCID: PMC7431035 DOI: 10.1073/pnas.1918797117] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Comparative developmental genetics indicate insect and mammalian forebrains form and function in comparable ways. However, these data are open to opposing interpretations that advocate either a single origin of the brain and its adaptive modification during animal evolution; or multiple, independent origins of the many different brains present in extant Bilateria. Here, we describe conserved regulatory elements that mediate the spatiotemporal expression of developmental control genes directing the formation and function of midbrain circuits in flies, mice, and humans. These circuits develop from corresponding midbrain-hindbrain boundary regions and regulate comparable behaviors for balance and motor control. Our findings suggest that conserved regulatory mechanisms specify cephalic circuits for sensory integration and coordinated behavior common to all animals that possess a brain. Corresponding attributes of neural development and function suggest arthropod and vertebrate brains may have an evolutionarily conserved organization. However, the underlying mechanisms have remained elusive. Here, we identify a gene regulatory and character identity network defining the deutocerebral–tritocerebral boundary (DTB) in Drosophila. This network comprises genes homologous to those directing midbrain-hindbrain boundary (MHB) formation in vertebrates and their closest chordate relatives. Genetic tracing reveals that the embryonic DTB gives rise to adult midbrain circuits that in flies control auditory and vestibular information processing and motor coordination, as do MHB-derived circuits in vertebrates. DTB-specific gene expression and function are directed by cis-regulatory elements of developmental control genes that include homologs of mammalian Zinc finger of the cerebellum and Purkinje cell protein 4. Drosophila DTB-specific cis-regulatory elements correspond to regulatory sequences of human ENGRAILED-2, PAX-2, and DACHSHUND-1 that direct MHB-specific expression in the embryonic mouse brain. We show that cis-regulatory elements and the gene networks they regulate direct the formation and function of midbrain circuits for balance and motor coordination in insects and mammals. Regulatory mechanisms mediating the genetic specification of cephalic neural circuits in arthropods correspond to those in chordates, thereby implying their origin before the divergence of deuterostomes and ecdysozoans.
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27
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Schmidbaur H, Schwaha T, Franzkoch R, Purschke G, Steiner G. Within-family plasticity of nervous system architecture in Syllidae (Annelida, Errantia). Front Zool 2020; 17:20. [PMID: 32582362 PMCID: PMC7310387 DOI: 10.1186/s12983-020-00359-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 04/03/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The ground pattern underlying the nervous system of the last common ancestor in annelids was long thought to be settled, consisting of a dorsal brain, circumoesophageal connectives and a subepithelial, ladder-like ventral nerve cord with segmental ganglia connected by paired connectives. With the advent of immunocytochemical stainings and confocal laser scanning microscopy, it becomes evident that its architecture is extremely diverse, which makes the reconstruction of a ground pattern in annelida challenging. Whereas the nervous systems of many different families has already been described, only very few studies looked at the diversity of nervous systems within such clades to give a closer estimate on how plastic the annelid nervous system really is. So far, little is known on syllid nervous system architecture, one of the largest and most diverse groups of marine annelids. RESULTS The position of the brain, the circumoesophageal connectives, the stomatogastric nervous system, the longitudinal nerves that traverse each segment and the innervation of appendages are relatively uniform within the clade. Both the number of connectives within the ventral nerve cord and the number of segmental nerves, which in earlier studies were used to infer phylogenetic relationships and to reconstruct an annelid ground pattern, are highly diverse and differ between genera or even within a given genus. Differences in the distribution of somata of the brain, the nuchal innervation and its associated cell bodies were found between Syllinae and Exogoninae and may be subfamily-specific. CONCLUSIONS The nervous system morphology of syllids very likely depends on the taxon-specific ecological requirements. Thus, it is not surprising that in a clade, which occupies such diverse niches as the Annelida, we find similar patterns in phylogenetically widely separated species in similar niches and a high degree of modularity within a family. Only standardized protocols and staining methods can lead to comparable results, but so far different approaches have been taken to describe annelid nervous systems, making homologization of certain structures difficult. This study provides the first thorough description of the nervous system in the family Syllidae, allowing more detailed comparisons between annelid families in the future.
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Affiliation(s)
- Hannah Schmidbaur
- Department of Integrative Zoology, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
- Present address: Department of Molecular Evolution and Development, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Thomas Schwaha
- Department of Integrative Zoology, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Rico Franzkoch
- Zoology and Developmental Biology, Department of Biology and Chemistry, University of Osnabrück, Barbarastr. 11, 49069 Osnabrück, Germany
- Present address: Microbiology, Department of Biology and Chemistry, University of Osnabrück, Barbarastr. 11, 49069 Osnabrück, Germany
| | - Günter Purschke
- Zoology and Developmental Biology, Department of Biology and Chemistry, University of Osnabrück, Barbarastr. 11, 49069 Osnabrück, Germany
| | - Gerhard Steiner
- Department of Integrative Zoology, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
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28
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Kon T, Furukawa T. Origin and evolution of the Rax homeobox gene by comprehensive evolutionary analysis. FEBS Open Bio 2020; 10:657-673. [PMID: 32144893 PMCID: PMC7137802 DOI: 10.1002/2211-5463.12832] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Revised: 02/26/2020] [Accepted: 03/04/2020] [Indexed: 12/20/2022] Open
Abstract
Rax is one of the key transcription factors crucial for vertebrate eye development. In this study, we conducted comprehensive evolutionary analysis of Rax. We found that Bilateria and Cnidaria possess Rax, but Placozoa, Porifera, and Ctenophora do not, implying that the origin of the Rax gene dates back to the common ancestor of Cnidaria and Bilateria. The results of molecular phylogenetic and synteny analyses on Rax loci between jawed and jawless vertebrates indicate that segmental duplication of the Rax locus occurred in an early common ancestor of jawed vertebrates, resulting in two Rax paralogs in jawed vertebrates, Rax and Rax2. By analyzing 86 mammalian genomes from all four major groups of mammals, we found that at least five independent Rax2 gene loss events occurred in mammals. This study may provide novel insights into the evolution of the eye.
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Affiliation(s)
- Tetsuo Kon
- Laboratory for Molecular and Developmental Biology, Institute for Protein Research, Osaka University, Suita, Japan
| | - Takahisa Furukawa
- Laboratory for Molecular and Developmental Biology, Institute for Protein Research, Osaka University, Suita, Japan
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29
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Liu B, Satou Y. The genetic program to specify ectodermal cells in ascidian embryos. Dev Growth Differ 2020; 62:301-310. [PMID: 32130723 DOI: 10.1111/dgd.12660] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Revised: 02/11/2020] [Accepted: 02/21/2020] [Indexed: 12/18/2022]
Abstract
The ascidian belongs to the sister group of vertebrates and shares many features with them. The gene regulatory network (GRN) controlling gene expression in ascidian embryonic development leading to the tadpole larva has revealed evolutionarily conserved gene circuits between ascidians and vertebrates. These conserved mechanisms are indeed useful to infer the original developmental programs of the ancestral chordates. Simultaneously, these studies have revealed which gene circuits are missing in the ascidian GRN; these gene circuits may have been acquired in the vertebrate lineage. In particular, the GRN responsible for gene expression in ectodermal cells of ascidian embryos has revealed the genetic programs that regulate the regionalization of the brain, formation of palps derived from placode-like cells, and differentiation of sensory neurons derived from neural crest-like cells. We here discuss how these studies have given insights into the evolution of these traits.
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Affiliation(s)
- Boqi Liu
- Department of Zoology, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Yutaka Satou
- Department of Zoology, Graduate School of Science, Kyoto University, Kyoto, Japan
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30
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Fields C, Bischof J, Levin M. Morphological Coordination: A Common Ancestral Function Unifying Neural and Non-Neural Signaling. Physiology (Bethesda) 2020; 35:16-30. [DOI: 10.1152/physiol.00027.2019] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Nervous systems are traditionally thought of as providing sensing and behavioral coordination functions at the level of the whole organism. What is the evolutionary origin of the mechanisms enabling the nervous systems’ information processing ability? Here, we review evidence from evolutionary, developmental, and regenerative biology suggesting a deeper, ancestral function of both pre-neural and neural cell-cell communication systems: the long-distance coordination of cell division and differentiation required to create and maintain body-axis symmetries. This conceptualization of the function of nervous system activity sheds new light on the evolutionary transition from the morphologically rudimentary, non-neural Porifera and Placazoa to the complex morphologies of Ctenophores, Cnidarians, and Bilaterians. It further allows a sharp formulation of the distinction between long-distance axis-symmetry coordination based on external coordinates, e.g., by whole-organism scale trophisms as employed by plants and sessile animals, and coordination based on body-centered coordinates as employed by motile animals. Thus we suggest that the systems that control animal behavior evolved from ancient mechanisms adapting preexisting ionic and neurotransmitter mechanisms to regulate individual cell behaviors during morphogenesis. An appreciation of the ancient, non-neural origins of bioelectrically mediated computation suggests new approaches to the study of embryological development, including embryological dysregulation, cancer, regenerative medicine, and synthetic bioengineering.
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Affiliation(s)
- Chris Fields
- 23 Rue des Lavandières, Caunes Minervois, France
| | - Johanna Bischof
- Allen Discovery Center at Tufts University, Medford, Massachusetts
| | - Michael Levin
- Allen Discovery Center at Tufts University, Medford, Massachusetts
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31
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Powell R, O'Malley MA. Metabolic and microbial perspectives on the "evolution of evolution". JOURNAL OF EXPERIMENTAL ZOOLOGY. PART B, MOLECULAR AND DEVELOPMENTAL EVOLUTION 2019; 332:321-330. [PMID: 31532063 DOI: 10.1002/jez.b.22898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 07/20/2019] [Accepted: 07/23/2019] [Indexed: 06/10/2023]
Abstract
Identifying and theorizing major turning points in the history of life generates insights into not only world-changing evolutionary events but also the processes that bring these events about. In his treatment of these issues, Bonner identifies the evolution of sex, multicellularity, and nervous systems as enabling the "evolution of evolution," which involves fundamental transformations in how evolution occurs. By contextualizing his framework within two decades of theorizing about major transitions in evolution, we identify some basic problems that Bonner's theory shares with much of the prevailing literature. These problems include implicit progressivism, theoretical disunity, and a limited ability to explain major evolutionary transformations. We go on to identify events and processes that are neglected by existing views. In contrast with the "vertical" focus on replication, hierarchy, and morphology that preoccupies most of the literature on major transitions, we propose a "horizontal" dimension in which metabolism and microbial innovations play a central explanatory role in understanding the broad-scale organization of life.
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Affiliation(s)
- Russell Powell
- Department of Philosophy, Boston University, Boston, Massachusetts
| | - Maureen A O'Malley
- School of History and Philosophy of Science, University of Bordeaux/University of Sydney, Sydney, Australia
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32
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Martín-Durán JM, Hejnol A. A developmental perspective on the evolution of the nervous system. Dev Biol 2019; 475:181-192. [PMID: 31610146 DOI: 10.1016/j.ydbio.2019.10.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2017] [Revised: 06/02/2018] [Accepted: 10/04/2019] [Indexed: 12/20/2022]
Abstract
The evolution of nervous systems in animals has always fascinated biologists, and thus multiple evolutionary scenarios have been proposed to explain the appearance of neurons and complex neuronal centers. However, the absence of a robust phylogenetic framework for animal interrelationships, the lack of a mechanistic understanding of development, and a recapitulative view of animal ontogeny have traditionally limited these scenarios. Only recently, the integration of advanced molecular and morphological studies in a broad range of animals has allowed to trace the evolution of developmental and neuronal characters on a better-resolved animal phylogeny. This has falsified most traditional scenarios for nervous system evolution, paving the way for the emergence of new testable hypotheses. Here we summarize recent progress in studies of nervous system development in major animal lineages and formulate some of the arising questions. In particular, we focus on how lineage analyses of nervous system development and a comparative study of the expression of neural-related genes has influenced our understanding of the evolution of an elaborated central nervous system in Bilateria. We argue that a phylogeny-guided study of neural development combining thorough descriptive and functional analyses is key to establish more robust scenarios for the origin and evolution of animal nervous systems.
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Affiliation(s)
- José M Martín-Durán
- Sars International Centre for Marine Molecular Biology, University of Bergen, Thørmohlensgate 55, 5006, Bergen, Norway; School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, E1 4NS, London, UK.
| | - Andreas Hejnol
- Sars International Centre for Marine Molecular Biology, University of Bergen, Thørmohlensgate 55, 5006, Bergen, Norway.
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33
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Fields C, Levin M. Somatic multicellularity as a satisficing solution to the prediction-error minimization problem. Commun Integr Biol 2019; 12:119-132. [PMID: 31413788 PMCID: PMC6682261 DOI: 10.1080/19420889.2019.1643666] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 07/04/2019] [Accepted: 07/07/2019] [Indexed: 11/26/2022] Open
Abstract
Adaptive success in the biosphere requires the dynamic ability to adjust physiological, transcriptional, and behavioral responses to environmental conditions. From chemical networks to organisms to whole communities, biological entities at all levels of organization seek to optimize their predictive power. Here, we argue that this fundamental drive provides a novel perspective on the origin of multicellularity. One way for unicellular organisms to minimize surprise with respect to external inputs is to be surrounded by reproductively-disabled, i.e. somatic copies of themselves - highly predictable agents which in effect reduce uncertainty in their microenvironments. We show that the transition to multicellularity can be modeled as a phase transition driven by environmental threats. We present modeling results showing how multicellular bodies can arise if non-reproductive somatic cells protect their reproductive parents from environmental lethality. We discuss how a somatic body can be interpreted as a Markov blanket around one or more reproductive cells, and how the transition to somatic multicellularity can be represented as a transition from exposure of reproductive cells to a high-uncertainty environment to their protection from environmental uncertainty by this Markov blanket. This is, effectively, a transition by the Markov blanket from transparency to opacity for the variational free energy of the environment. We suggest that the ability to arrest the cell cycle of daughter cells and redirect their resource utilization from division to environmental threat amelioration is the key innovation of obligate multicellular eukaryotes, that the nervous system evolved to exercise this control over long distances, and that cancer is an escape by somatic cells from the control of reproductive cells. Our quantitative model illustrates the evolutionary dynamics of this system, provides a novel hypothesis for the origin of multicellular animal bodies, and suggests a fundamental link between the architectures of complex organisms and information processing in proto-cognitive cellular agents.
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Affiliation(s)
| | - Michael Levin
- Allen Discovery Center at Tufts University, Medford, MA USA
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34
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Leung B, Shimeld SM. Evolution of vertebrate spinal cord patterning. Dev Dyn 2019; 248:1028-1043. [PMID: 31291046 DOI: 10.1002/dvdy.77] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 06/14/2019] [Accepted: 06/15/2019] [Indexed: 12/17/2022] Open
Abstract
The vertebrate spinal cord is organized across three developmental axes, anterior-posterior (AP), dorsal-ventral (DV), and medial-lateral (ML). Patterning of these axes is regulated by canonical intercellular signaling pathways: the AP axis by Wnt, fibroblast growth factor, and retinoic acid (RA), the DV axis by Hedgehog, Tgfβ, and Wnt, and the ML axis where proliferation is controlled by Notch. Developmental time plays an important role in which signal does what and when. Patterning across the three axes is not independent, but linked by interactions between signaling pathway components and their transcriptional targets. Combined this builds a sophisticated organ with many different types of cell in specific AP, DV, and ML positions. Two living lineages share phylum Chordata with vertebrates, amphioxus, and tunicates, while the jawless fish such as lampreys, survive as the most basally divergent vertebrate lineage. Genes and mechanisms shared between lampreys and other vertebrates tell us what predated vertebrates, while those also shared with other chordates tell us what evolved early in chordate evolution. Between these lie vertebrate innovations: genetic and developmental changes linked to evolution of new morphology. These include gene duplications, differences in how signals are received, and new regulatory connections between signaling pathways and their target genes.
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Affiliation(s)
- Brigid Leung
- Department of Zoology, University of Oxford, Oxford, UK
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35
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BMP controls dorsoventral and neural patterning in indirect-developing hemichordates providing insight into a possible origin of chordates. Proc Natl Acad Sci U S A 2019; 116:12925-12932. [PMID: 31189599 DOI: 10.1073/pnas.1901919116] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A defining feature of chordates is the unique presence of a dorsal hollow neural tube that forms by internalization of the ectodermal neural plate specified via inhibition of BMP signaling during gastrulation. While BMP controls dorsoventral (DV) patterning across diverse bilaterians, the BMP-active side is ventral in chordates and dorsal in many other bilaterians. How this phylum-specific DV inversion occurs and whether it is coupled to the emergence of the dorsal neural plate are unknown. Here we explore these questions by investigating an indirect-developing enteropneust from the hemichordate phylum, which together with echinoderms form a sister group of the chordates. We found that in the hemichordate larva, BMP signaling is required for DV patterning and is sufficient to repress neurogenesis. We also found that transient overactivation of BMP signaling during gastrulation concomitantly blocked mouth formation and centralized the nervous system to the ventral ectoderm in both hemichordate and sea urchin larvae. Moreover, this mouthless, neurogenic ventral ectoderm displayed a medial-to-lateral organization similar to that of the chordate neural plate. Thus, indirect-developing deuterostomes use BMP signaling in DV and neural patterning, and an elevated BMP level during gastrulation drives pronounced morphological changes reminiscent of a DV inversion. These findings provide a mechanistic basis to support the hypothesis that an inverse chordate body plan emerged from an indirect-developing ancestor by tinkering with BMP signaling.
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36
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Leclère L, Horin C, Chevalier S, Lapébie P, Dru P, Peron S, Jager M, Condamine T, Pottin K, Romano S, Steger J, Sinigaglia C, Barreau C, Quiroga Artigas G, Ruggiero A, Fourrage C, Kraus JEM, Poulain J, Aury JM, Wincker P, Quéinnec E, Technau U, Manuel M, Momose T, Houliston E, Copley RR. The genome of the jellyfish Clytia hemisphaerica and the evolution of the cnidarian life-cycle. Nat Ecol Evol 2019; 3:801-810. [PMID: 30858591 DOI: 10.1038/s41559-019-0833-2] [Citation(s) in RCA: 81] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 01/30/2019] [Indexed: 12/14/2022]
Abstract
Jellyfish (medusae) are a distinctive life-cycle stage of medusozoan cnidarians. They are major marine predators, with integrated neurosensory, muscular and organ systems. The genetic foundations of this complex form are largely unknown. We report the draft genome of the hydrozoan jellyfish Clytia hemisphaerica and use multiple transcriptomes to determine gene use across life-cycle stages. Medusa, planula larva and polyp are each characterized by distinct transcriptome signatures reflecting abrupt life-cycle transitions and all deploy a mixture of phylogenetically old and new genes. Medusa-specific transcription factors, including many with bilaterian orthologues, associate with diverse neurosensory structures. Compared to Clytia, the polyp-only hydrozoan Hydra has lost many of the medusa-expressed transcription factors, despite similar overall rates of gene content evolution and sequence evolution. Absence of expression and gene loss among Clytia orthologues of genes patterning the anthozoan aboral pole, secondary axis and endomesoderm support simplification of planulae and polyps in Hydrozoa, including loss of bilateral symmetry. Consequently, although the polyp and planula are generally considered the ancestral cnidarian forms, in Clytia the medusa maximally deploys the ancestral cnidarian-bilaterian transcription factor gene complement.
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Affiliation(s)
- Lucas Leclère
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche-sur-mer, France
| | - Coralie Horin
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche-sur-mer, France
| | - Sandra Chevalier
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche-sur-mer, France
| | - Pascal Lapébie
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche-sur-mer, France.,Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, Marseille, France
| | - Philippe Dru
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche-sur-mer, France
| | - Sophie Peron
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche-sur-mer, France
| | - Muriel Jager
- Evolution Paris-Seine, Institut de Biologie Paris-Seine, Sorbonne Université, CNRS, Paris, France.,Institut de Systématique, Evolution, Biodiversité (ISYEB UMR 7205), Sorbonne Université, MNHN, CNRS, EPHE, Paris, France
| | - Thomas Condamine
- Evolution Paris-Seine, Institut de Biologie Paris-Seine, Sorbonne Université, CNRS, Paris, France
| | - Karen Pottin
- Evolution Paris-Seine, Institut de Biologie Paris-Seine, Sorbonne Université, CNRS, Paris, France.,Laboratoire de Biologie du Développement (IBPS-LBD, UMR7622), Sorbonne Université, CNRS, Institut de Biologie Paris Seine, Paris, France
| | - Séverine Romano
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche-sur-mer, France
| | - Julia Steger
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche-sur-mer, France.,Laboratoire de Biologie du Développement (IBPS-LBD, UMR7622), Sorbonne Université, CNRS, Institut de Biologie Paris Seine, Paris, France
| | - Chiara Sinigaglia
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche-sur-mer, France.,Institut de Génomique Fonctionnelle de Lyon, École Normale Supérieure de Lyon, CNRS UMR 5242-INRA USC 1370, Lyon cedex 07, France
| | - Carine Barreau
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche-sur-mer, France
| | - Gonzalo Quiroga Artigas
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche-sur-mer, France.,The Whitney Laboratory for Marine Bioscience, University of Florida, St. Augustine, FL, USA
| | - Antonella Ruggiero
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche-sur-mer, France.,Centre de Recherche de Biologie cellulaire de Montpellier, CNRS UMR 5237, Université de Montpellier, Montpellier Cedex 5, France
| | - Cécile Fourrage
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche-sur-mer, France.,Service de Génétique UMR 781, Hôpital Necker-APHP, Paris, France
| | - Johanna E M Kraus
- Department for Molecular Evolution and Development, Centre of Organismal Systems Biology, University of Vienna, Vienna, Austria.,Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Julie Poulain
- Génomique Métabolique, Genoscope, Institut François Jacob, CEA, CNRS, Univ Evry, Université Paris-Saclay, Evry, France
| | - Jean-Marc Aury
- Genoscope, Institut de Biologie François-Jacob, Commissariat à l'Energie Atomique, Université Paris-Saclay, Evry, France
| | - Patrick Wincker
- Génomique Métabolique, Genoscope, Institut François Jacob, CEA, CNRS, Univ Evry, Université Paris-Saclay, Evry, France
| | - Eric Quéinnec
- Evolution Paris-Seine, Institut de Biologie Paris-Seine, Sorbonne Université, CNRS, Paris, France.,Institut de Systématique, Evolution, Biodiversité (ISYEB UMR 7205), Sorbonne Université, MNHN, CNRS, EPHE, Paris, France
| | - Ulrich Technau
- Department for Molecular Evolution and Development, Centre of Organismal Systems Biology, University of Vienna, Vienna, Austria
| | - Michaël Manuel
- Evolution Paris-Seine, Institut de Biologie Paris-Seine, Sorbonne Université, CNRS, Paris, France.,Institut de Systématique, Evolution, Biodiversité (ISYEB UMR 7205), Sorbonne Université, MNHN, CNRS, EPHE, Paris, France
| | - Tsuyoshi Momose
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche-sur-mer, France
| | - Evelyn Houliston
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche-sur-mer, France
| | - Richard R Copley
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche-sur-mer, France.
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Bahrampour S, Jonsson C, Thor S. Brain expansion promoted by polycomb-mediated anterior enhancement of a neural stem cell proliferation program. PLoS Biol 2019; 17:e3000163. [PMID: 30807568 PMCID: PMC6407790 DOI: 10.1371/journal.pbio.3000163] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 03/08/2019] [Accepted: 02/08/2019] [Indexed: 12/31/2022] Open
Abstract
During central nervous system (CNS) development, genetic programs establish neural stem cells and drive both stem and daughter cell proliferation. However, the prominent anterior expansion of the CNS implies anterior–posterior (A–P) modulation of these programs. In Drosophila, a set of neural stem cell factors acts along the entire A–P axis to establish neural stem cells. Brain expansion results from enhanced stem and daughter cell proliferation, promoted by a Polycomb Group (PcG)->Homeobox (Hox) homeotic network. But how does PcG->Hox modulate neural-stem-cell–factor activity along the A–P axis? We find that the PcG->Hox network creates an A–P expression gradient of neural stem cell factors, thereby driving a gradient of proliferation. PcG mutants can be rescued by misexpression of the neural stem cell factors or by mutation of one single Hox gene. Hence, brain expansion results from anterior enhancement of core neural-stem-cell–factor expression, mediated by PcG repression of brain Hox expression. A study in fruit flies shows that the anterior expansion of the central nervous system, to form the brain, is driven by Polycomb-mediated repression of Hox genes, resulting in anterior enhancement of a neural stem cell program. The central nervous system displays a pronounced anterior expansion that forms the brain. In the fruit fly Drosophila melanogaster, this expansion is driven by enhanced anterior cell proliferation. Recent studies reveal that cell proliferation in the brain is promoted by the Polycomb Group Complex, a key epigenetic complex. During development of the central nervous system, the Polycomb Group Complex acts to exclude Hox homeotic gene expression from the brain, thereby rendering the brain a Hox-free zone. Hox genes act in an antiproliferative manner, which explains the hyperproliferation observed in the brain, as well as the gradient of proliferation along the anterior–posterior axis of the central nervous system. Here, we find that Hox genes act by repressing a common neural stem cell proliferation program in more posterior regions, resulting in an anterior–posterior gradient of “stemness.” Hence, elevated anterior proliferation is promoted by the Polycomb Group Complex acting to keep the brain free of negative Hox input, thereby ensuring elevated expression of neural stem cell factors in the brain. Strikingly, mutants of the Polycomb Group Complex can be rescued by mutation of one single Hox gene, demonstrating that the primary role of the Polycomb Group Complex is indeed Hox repression. This study advances our understanding of how neural stem cell programs operate at different axial levels of the central nervous system and may have implications also for stem cell and organoid biology.
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Affiliation(s)
- Shahrzad Bahrampour
- Department of Clinical and Experimental Medicine, Linkoping University, Linkoping, Sweden
| | - Carolin Jonsson
- Department of Clinical and Experimental Medicine, Linkoping University, Linkoping, Sweden
| | - Stefan Thor
- Department of Clinical and Experimental Medicine, Linkoping University, Linkoping, Sweden
- School of Biomedical Sciences, University of Queensland, St. Lucia, Queensland, Australia
- * E-mail:
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38
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Lara-Ramirez R, Pérez-González C, Anselmi C, Patthey C, Shimeld SM. A Notch-regulated proliferative stem cell zone in the developing spinal cord is an ancestral vertebrate trait. Development 2019; 146:dev.166595. [PMID: 30552127 DOI: 10.1242/dev.166595] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 11/26/2018] [Indexed: 01/01/2023]
Abstract
Vertebrates have evolved the most sophisticated nervous systems we know. These differ from the nervous systems of invertebrates in several ways, including the evolution of new cell types, and the emergence and elaboration of patterning mechanisms to organise cells in time and space. Vertebrates also generally have many more cells in their central nervous systems than invertebrates, and an increase in neural cell number may have contributed to the sophisticated anatomy of the brain and spinal cord. Here, we study how increased cell number evolved in the vertebrate central nervous system, investigating the regulation of cell proliferation in the lamprey spinal cord. Markers of proliferation show that a ventricular progenitor zone is found throughout the lamprey spinal cord. We show that inhibition of Notch signalling disrupts the maintenance of this zone. When Notch is blocked, progenitor cells differentiate precociously, the proliferative ventricular zone is lost and differentiation markers become expressed throughout the spinal cord. Comparison with other chordates suggests that the emergence of a persistent Notch-regulated proliferative progenitor zone was a crucial step for the evolution of vertebrate spinal cord complexity.
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Affiliation(s)
- Ricardo Lara-Ramirez
- Department of Zoology, University of Oxford, 11a Mansfield Road, Oxford OX1 3SZ, UK
| | | | - Chiara Anselmi
- Department of Zoology, University of Oxford, 11a Mansfield Road, Oxford OX1 3SZ, UK
| | - Cedric Patthey
- Department of Zoology, University of Oxford, 11a Mansfield Road, Oxford OX1 3SZ, UK
| | - Sebastian M Shimeld
- Department of Zoology, University of Oxford, 11a Mansfield Road, Oxford OX1 3SZ, UK
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Abstract
Social monogamy, typically characterized by the formation of a pair bond, increased territorial defense, and often biparental care, has independently evolved multiple times in animals. Despite the independent evolutionary origins of monogamous mating systems, several homologous brain regions and neuropeptides and their receptors have been shown to play a conserved role in regulating social affiliation and parental care, but little is known about the neuromolecular mechanisms underlying monogamy on a genomic scale. Here, we compare neural transcriptomes of reproductive males in monogamous and nonmonogamous species pairs of Peromyscus mice, Microtus voles, parid songbirds, dendrobatid frogs, and Xenotilapia species of cichlid fishes. We find that, while evolutionary divergence time between species or clades did not explain gene expression similarity, characteristics of the mating system correlated with neural gene expression patterns, and neural gene expression varied concordantly across vertebrates when species transition to monogamy. Our study provides evidence of a universal transcriptomic mechanism underlying the evolution of monogamy in vertebrates.
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Abstract
Epigenetic mechanisms, including DNA and histone modifications, are pivotal for normal brain development and functions by modulating spatial and temporal gene expression. Dysregulation of the epigenetic machinery can serve as a causal role in numerous brain disorders. Proper mammalian brain development and functions depend on the precise expression of neuronal-specific genes, transcription factors and epigenetic modifications. Antagonistic polycomb and trithorax proteins form multimeric complexes and play important roles in these processes by epigenetically controlling gene repression or activation through various molecular mechanisms. Aberrant expression or disruption of either protein group can contribute to neurodegenerative diseases. This review focus on the current progress of Polycomb and Trithorax complexes in brain development and disease, and provides a future outlook of the field.
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41
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Formery L, Schubert M, Croce JC. Ambulacrarians and the Ancestry of Deuterostome Nervous Systems. Results Probl Cell Differ 2019; 68:31-59. [PMID: 31598852 DOI: 10.1007/978-3-030-23459-1_3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The evolutionary origin and history of metazoan nervous systems has been at the heart of numerous scientific debates for well over a century. This has been a particularly difficult issue to resolve within the deuterostomes, chiefly due to the distinct neural architectures observed within this group of animals. Indeed, deuterosomes feature central nervous systems, apical organs, nerve cords, and basiepidermal nerve nets. Comparative analyses investigating the anatomy and molecular composition of deuterostome nervous systems have nonetheless succeeded in identifying a number of shared and derived features. These analyses have led to the elaboration of diverse theories about the origin and evolutionary history of deuterostome nervous systems. Here, we provide an overview of these distinct theories. Further, we argue that deciphering the adult nervous systems of representatives of all deuterostome phyla, including echinoderms, which have long been neglected in this type of surveys, will ultimately provide answers to the questions concerning the ancestry and evolution of deuterostome nervous systems.
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Affiliation(s)
- Laurent Formery
- Sorbonne Université, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-Mer (LBDV), Evolution of Intercellular Signaling in Development (EvoInSiDe) Team, Villefranche-sur-Mer, France
| | - Michael Schubert
- Sorbonne Université, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-Mer (LBDV), Evolution of Intercellular Signaling in Development (EvoInSiDe) Team, Villefranche-sur-Mer, France
| | - Jenifer C Croce
- Sorbonne Université, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-Mer (LBDV), Evolution of Intercellular Signaling in Development (EvoInSiDe) Team, Villefranche-sur-Mer, France.
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42
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Irie N, Satoh N, Kuratani S. The phylum Vertebrata: a case for zoological recognition. ZOOLOGICAL LETTERS 2018; 4:32. [PMID: 30607258 PMCID: PMC6307173 DOI: 10.1186/s40851-018-0114-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Accepted: 12/05/2018] [Indexed: 06/09/2023]
Abstract
The group Vertebrata is currently placed as a subphylum in the phylum Chordata, together with two other subphyla, Cephalochordata (lancelets) and Urochordata (ascidians). The past three decades, have seen extraordinary advances in zoological taxonomy and the time is now ripe for reassessing whether the subphylum position is truly appropriate for vertebrates, particularly in light of recent advances in molecular phylogeny, comparative genomics, and evolutionary developmental biology. Four lines of current research are discussed here. First, molecular phylogeny has demonstrated that Deuterostomia comprises Ambulacraria (Echinodermata and Hemichordata) and Chordata (Cephalochordata, Urochordata, and Vertebrata), each clade being recognized as a mutually comparable phylum. Second, comparative genomic studies show that vertebrates alone have experienced two rounds of whole-genome duplication, which makes the composition of their gene family unique. Third, comparative gene-expression profiling of vertebrate embryos favors an hourglass pattern of development, the most conserved stage of which is recognized as a phylotypic period characterized by the establishment of a body plan definitively associated with a phylum. This mid-embryonic conservation is supported robustly in vertebrates, but only weakly in chordates. Fourth, certain complex patterns of body plan formation (especially of the head, pharynx, and somites) are recognized throughout the vertebrates, but not in any other animal groups. For these reasons, we suggest that it is more appropriate to recognize vertebrates as an independent phylum, not as a subphylum of the phylum Chordata.
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Affiliation(s)
- Naoki Irie
- Department of Biological Sciences, School of Science, University of Tokyo, Tokyo, 113-0033 Japan
- Universal Biology Institute, University of Tokyo, Tokyo, 113-0033 Japan
| | - Noriyuki Satoh
- Marine Genomics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, 904-0495 Japan
| | - Shigeru Kuratani
- Laboratory for Evolutionary Morphology, RIKEN Center for Biosystems Dynamics Research, and Evolutionary Morphology Laboratory, RIKEN Cluster for Pioneering Research, 2-2-3 Minatojima-minami, Chuo-ku, Kobe, 650-0047 Japan
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43
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Zhao D, Chen S, Liu X. Lateral neural borders as precursors of peripheral nervous systems: A comparative view across bilaterians. Dev Growth Differ 2018; 61:58-72. [DOI: 10.1111/dgd.12585] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2018] [Revised: 11/14/2018] [Accepted: 11/14/2018] [Indexed: 01/13/2023]
Affiliation(s)
- Di Zhao
- School of Life Sciences; Capital Normal University; Beijing China
- Ministry of Education Key Laboratory of Bioinformatics; Center for Synthetic and Systems Biology; School of Life Sciences; Tsinghua University; Beijing China
| | - Siyu Chen
- Ministry of Education Key Laboratory of Bioinformatics; Center for Synthetic and Systems Biology; School of Life Sciences; Tsinghua University; Beijing China
| | - Xiao Liu
- School of Life Sciences; Capital Normal University; Beijing China
- Ministry of Education Key Laboratory of Bioinformatics; Center for Synthetic and Systems Biology; School of Life Sciences; Tsinghua University; Beijing China
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Behavioral Role of the Reciprocal Inhibition between a Pair of Mauthner Cells during Fast Escapes in Zebrafish. J Neurosci 2018; 39:1182-1194. [PMID: 30578342 DOI: 10.1523/jneurosci.1964-18.2018] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 12/13/2018] [Accepted: 12/16/2018] [Indexed: 11/21/2022] Open
Abstract
During many behaviors in vertebrates, the CNS generates asymmetric activities between the left and right sides to produce asymmetric body movements. For asymmetrical activations of the CNS, reciprocal inhibition between the left and right sides is believed to play a key role. However, the complexity of the CNS makes it difficult to identify the reciprocal inhibition circuits at the level of individual cells and the contribution of each neuron to the asymmetric activity. Using larval zebrafish, we examined this issue by investigating reciprocal inhibition circuits between a pair of Mauthner (M) cells, giant reticulospinal neurons that trigger fast escapes. Previous studies have shown that a class of excitatory neurons, called cranial relay neurons, is involved in the reciprocal inhibition pathway between the M cells. Using transgenic fish, in which two of the cranial relay neurons (Ta1 and Ta2) expressed GFP, we showed that Ta1 and Ta2 constitute major parts of the pathway. In larvae in which Ta1/Ta2 were laser-ablated, the amplitude of the reciprocal IPSPs dropped to less than one-third. Calcium imaging and electrophysiological recording showed that the occurrence probability of bilateral M-cell activation upon sound/vibration stimuli was greatly increased in the Ta1/Ta2-ablated larvae. Behavioral experiments revealed that the Ta1/Ta2 ablation resulted in shallower body bends during sound/vibration-evoked escapes, which is consistent with the observation that increased occurrence of bilateral M-cell activation impaired escape performance. Our study revealed major components of the reciprocal inhibition circuits in the M cell system and the behavioral importance of the circuits.SIGNIFICANCE STATEMENT Reciprocal inhibition between the left and right side of the CNS is considered imperative for producing asymmetric movements in animals. It has been difficult, however, to identify the circuits at the individual cell level and their role in behavior. Here, we address this problem by examining the reciprocal inhibition circuits of the hindbrain Mauthner (M) cell system in larval zebrafish. We determined that two paired interneurons play a critical role in the reciprocal inhibition between the paired M cells and that the reciprocal inhibition prevents bilateral firing of the M cells and is thus necessary for the full body bend during M cell-initiated escape. Further, we discussed the cooperation of multiple reciprocal inhibitions working in the hindbrain and spinal cord to ensure high-performance escapes.
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45
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Bailey DM. Oxygen, evolution and redox signalling in the human brain; quantum in the quotidian. J Physiol 2018; 597:15-28. [PMID: 30315729 DOI: 10.1113/jp276814] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 09/27/2018] [Indexed: 12/20/2022] Open
Abstract
Rising atmospheric oxygen (O2 ) levels provided a selective pressure for the evolution of O2 -dependent micro-organisms that began with the autotrophic eukaryotes. Since these primordial times, the respiring mammalian cell has become entirely dependent on the constancy of electron flow, with molecular O2 serving as the terminal electron acceptor in mitochondrial oxidative phosphorylation. Indeed, the ability to 'sense' O2 and maintain homeostasis is considered one of the most important roles of the central nervous system (CNS) and probably represented a major driving force in the evolution of the human brain. Today, modern humans have evolved with an oversized brain committed to a continually active state and, as a consequence, paradoxically vulnerable to failure if the O2 supply is interrupted. However, our pre-occupation with O2 , the elixir of life, obscures the fact that it is a gas with a Janus face, capable of sustaining life in physiologically controlled amounts yet paradoxically deadly to the CNS when in excess. A closer look at its quantum structure reveals precisely why; the triplet ground state diatomic O2 molecule is paramagnetic and exists in air as a free radical, constrained from reacting aggressively with the brain's organic molecules due to its 'spin restriction', a thermodynamic quirk of evolutionary fate. By further exploring O2 's free radical 'quantum quirkiness', including emergent (quantum) physiological phenomena, our understanding of precisely how the human brain senses O2 deprivation (hypoxia) and the elaborate redox-signalling defence mechanisms that defend O2 homeostasis has the potential to offer unique insights into the pathophysiology and treatment of human brain disease.
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Affiliation(s)
- Damian Miles Bailey
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Wales, UK
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46
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Prünster MM, Ricci L, Brown FD, Tiozzo S. De novo neurogenesis in a budding chordate: Co-option of larval anteroposterior patterning genes in a transitory neurogenic organ. Dev Biol 2018; 448:342-352. [PMID: 30563648 DOI: 10.1016/j.ydbio.2018.10.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 08/29/2018] [Accepted: 10/16/2018] [Indexed: 01/29/2023]
Abstract
During metamorphosis of solitary ascidians, part of the larval tubular nervous system is recruited to form the adult central nervous system (CNS) through neural stem-like cells called ependymal cells. The anteroposterior (AP) gene expression patterning of the larval CNS regionalize the distribution of the ependymal cells, which contains the positional information of the neurons of the adult nervous system. In colonial ascidians, the CNS of asexually developed zooids has the same morphology of the one of the post-metamorphic zooids. However, its development follows a completely different organogenesis that lacks embryogenesis, a larval phase and metamorphosis. In order to describe neurogenesis during asexual development (blastogenesis), we followed the expression of six CNS AP patterning genes conserved in chordates and five neural-related genes to determine neural cell identity in Botryllus schlosseri. We observed that a neurogenesis occurs de novo on each blastogenic cycle starting from a neurogenic transitory structure, the dorsal tube. The dorsal tube partially co-opts the AP patterning of the larval CNS markers, and potentially combine the neurogenesis role and provider of positional clues for neuron patterning. This study shows how a larval developmental module is reused in a direct asexual development in order to generate the same structures.
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Affiliation(s)
- Maria Mandela Prünster
- Sorbonne Universités, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), 06230 Paris, France
| | - Lorenzo Ricci
- Sorbonne Universités, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), 06230 Paris, France; Harvard University, Department of Organismic&Evolutionary Biology, 52 Oxford Street, Cambridge, MA 02138, United States
| | - Federico D Brown
- Departamento de Zoologia - Instituto Biociências, Universidade de São Paulo, São Paulo, SP CEP 05508-090, Brazil; Centro de Biologia Marinha (CEBIMar), Universidade de São Paulo, São Sebastião, SP CEP 11612-109, Brazil
| | - Stefano Tiozzo
- Sorbonne Universités, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), 06230 Paris, France.
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47
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Escriva H. My Favorite Animal, Amphioxus: Unparalleled for Studying Early Vertebrate Evolution. Bioessays 2018; 40:e1800130. [PMID: 30328120 DOI: 10.1002/bies.201800130] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 09/07/2018] [Indexed: 01/08/2023]
Abstract
Amphioxus represents the most basally divergent group in chordates and probably the best extant proxy to the ancestor of all chordates including vertebrates. The amphioxus, or lancelets, are benthic filter feeding marine animals and their interest as a model in research is due to their phylogenetic position and their anatomical and genetic stasis throughout their evolutionary history. From the first works in the 19th century to the present day, enormous progress is made mainly favored by technical development at different levels, from spawning induction and husbandry techniques, through techniques for studies of gene function or of the role of different signalling pathways through embryonic development, to functional genomics techniques. Together, these advances foretell a plethora of interesting developments in the world of research with the amphioxus model. Here, the discovery and development of amphioxus as a superb model organism in evolutionary and evolutionary-developmental biology are reviewed.
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Affiliation(s)
- Hector Escriva
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins, BIOM, Banyuls-sur-Mer, F-66650, France
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48
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Bailey DM. RETRACTED ARTICLE: The quantum physiology of oxygen; from electrons to the evolution of redox signaling in the human brain. Bioelectron Med 2018; 4:13. [PMID: 32232089 PMCID: PMC7098224 DOI: 10.1186/s42234-018-0014-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 09/19/2018] [Indexed: 12/11/2022] Open
Abstract
Rising atmospheric oxygen (O2) levels provided a selective pressure for the evolution of O2-dependent micro-organisms that began with the autotrophic eukaryotes. Since these primordial times, the respiring mammalian cell has become entirely dependent on the constancy of electron flow with molecular O2 serving as the terminal electron acceptor in mitochondrial oxidative phosphorylation. Indeed, the ability to “sense” O2 and maintain homeostasis is considered one of the most important roles of the central nervous system (CNS) and likely represented a major driving force in the evolution of the human brain. Today, modern humans have evolved with an oversized brain committed to a continually active state and as a consequence, paradoxically vulnerable to failure if the O2 supply is interrupted. However, our pre-occupation with O2, the elixir of life, obscures the fact that it is a gas with a Janus Face, capable of sustaining life in physiologically controlled amounts yet paradoxically deadly to the CNS when in excess. A closer look at its quantum structure reveals precisely why; the triplet ground state diatomic O2 molecule is paramagnetic and exists in air as a free radical, constrained from reacting aggressively with the brain’s organic molecules due to its “spin restriction”, a thermodynamic quirk of evolutionary fate. By further exploring O2’s free radical “quantum quirkiness” including emergent quantum physiological phenomena, our understanding of precisely how the human brain senses O2 deprivation (hypoxia) and the elaborate redox-signaling defense mechanisms that defend O2 homeostasis has the potential to offer unique insights into the pathophysiology and treatment of human brain disease.
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Affiliation(s)
- Damian Miles Bailey
- Neurovascular Research Laboratory, Alfred Russel Wallace Building, Faculty of Life Sciences and Education, University of South Wales, Pontypridd, CF37 4AT UK
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49
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Helm C, Beckers P, Bartolomaeus T, Drukewitz SH, Kourtesis I, Weigert A, Purschke G, Worsaae K, Struck TH, Bleidorn C. Convergent evolution of the ladder-like ventral nerve cord in Annelida. Front Zool 2018; 15:36. [PMID: 30275868 PMCID: PMC6161469 DOI: 10.1186/s12983-018-0280-y] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Accepted: 09/04/2018] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND A median, segmented, annelid nerve cord has repeatedly been compared to the arthropod and vertebrate nerve cords and became the most used textbook representation of the annelid nervous system. Recent phylogenomic analyses, however, challenge the hypothesis that a subepidermal rope-ladder-like ventral nerve cord (VNC) composed of a paired serial chain of ganglia and somata-free connectives represents either a plesiomorphic or a typical condition in annelids. RESULTS Using a comparative approach by combining phylogenomic analyses with morphological methods (immunohistochemistry and CLSM, histology and TEM), we compiled a comprehensive dataset to reconstruct the evolution of the annelid VNC. Our phylogenomic analyses generally support previous topologies. However, the so far hard-to-place Apistobranchidae and Psammodrilidae are now incorporated among the basally branching annelids with high support. Based on this topology we reconstruct an intraepidermal VNC as the ancestral state in Annelida. Thus, a subepidermal ladder-like nerve cord clearly represents a derived condition. CONCLUSIONS Based on the presented data, a ladder-like appearance of the ventral nerve cord evolved repeatedly, and independently of the transition from an intraepidermal to a subepidermal cord during annelid evolution. Our investigations thereby propose an alternative set of neuroanatomical characteristics for the last common ancestor of Annelida or perhaps even Spiralia.
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Affiliation(s)
- Conrad Helm
- Animal Evolution and Biodiversity, Georg-August-University Göttingen, 37073 Göttingen, Germany
| | - Patrick Beckers
- Institute of Evolutionary Biology and Ecology, University of Bonn, 53121 Bonn, Germany
| | - Thomas Bartolomaeus
- Institute of Evolutionary Biology and Ecology, University of Bonn, 53121 Bonn, Germany
| | | | - Ioannis Kourtesis
- Animal Evolution and Biodiversity, Georg-August-University Göttingen, 37073 Göttingen, Germany
| | - Anne Weigert
- Department of Evolutionary Genetics, Max Planck Institute for Evolutionary Anthropology, 04103 Leipzig, Germany
| | - Günter Purschke
- Department of Developmental Biology and Zoology, University of Osnabrück, 49069 Osnabrück, Germany
| | - Katrine Worsaae
- Department of Biology, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Torsten H. Struck
- Frontiers in Evolutionary Zoology, Natural History Museum, University of Oslo, P.O. Box 1172, Blindern, NO-0318 Oslo, Norway
| | - Christoph Bleidorn
- Animal Evolution and Biodiversity, Georg-August-University Göttingen, 37073 Göttingen, Germany
- German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103 Leipzig, Germany
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50
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Deryckere A, Seuntjens E. The Cephalopod Large Brain Enigma: Are Conserved Mechanisms of Stem Cell Expansion the Key? Front Physiol 2018; 9:1160. [PMID: 30246785 PMCID: PMC6110919 DOI: 10.3389/fphys.2018.01160] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 08/02/2018] [Indexed: 12/19/2022] Open
Abstract
Within the clade of mollusks, cephalopods have developed an unusually large and complex nervous system. The increased complexity of the cephalopod centralized "brain" parallels an amazing amount of complex behaviors that culminate in one order, the octopods. The mechanisms that enable evolution of expanded brains in invertebrates remain enigmatic. While expression mapping of known molecular pathways demonstrated the conservation of major neurogenesis pathways and revealed neurogenic territories, it did not explain why cephalopods could massively increase their brain size compared to other mollusks. Such an increase is reminiscent of the expansion of the cerebral cortex in mammalians, which have enlarged their number and variety of neurogenic stem cells. We hypothesize that similar mechanisms might be at play in cephalopods and that focusing on the stem cell biology of cephalopod neurogenesis and genetic innovations might be smarter strategies to uncover the mechanism that has driven cephalopod brain expansion.
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Affiliation(s)
| | - Eve Seuntjens
- Laboratory of Developmental Neurobiology, Department of Biology, KU Leuven, Leuven, Belgium
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