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Borba C, Kourakis MJ, Miao Y, Guduri B, Deng J, Smith WC. Whole Nervous System Expression of Glutamate Receptors Reveals Distinct Receptor Roles in Sensorimotor Circuits. eNeuro 2024; 11:ENEURO.0306-24.2024. [PMID: 39256043 PMCID: PMC11419600 DOI: 10.1523/eneuro.0306-24.2024] [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: 07/08/2024] [Revised: 08/13/2024] [Accepted: 08/26/2024] [Indexed: 09/12/2024] Open
Abstract
The goal of connectomics is to reveal the links between neural circuits and behavior. Larvae of the primitive chordate Ciona are well-suited to make contributions in this area. In addition to having a described connectome, Ciona larvae have a range of readily quantified behaviors. Moreover, the small number of neurons in the larval CNS (∼180) holds the promise of a comprehensive characterization of individual neurons. We present single-neuron predictions for glutamate receptor (GlutR) expression based on in situ hybridization. Included are both ionotropic receptors (AMPA, NMDA, and kainate) and metabotropic receptors. The predicted glutamate receptor expression dataset is discussed in the context of known circuits driving behaviors such as phototaxis, mechanosensation, and looming shadow response. The predicted expression of AMPA and NMDA receptors may help resolve issues regarding the co-production of GABA and glutamate by a subset of photoreceptors. The targets of these photoreceptors in the midbrain appear to express NMDA receptors, but not AMPA receptors. This is in agreement with previous results indicating that GABA is the primary neurotransmitter from the photoreceptors evoking a swimming response through a disinhibition mechanism and that glutamate may, therefore, have only a modulatory action in this circuit. Other findings reported here are more unexpected. For example, many of the targets of glutamatergic epidermal sensory neurons (ESNs) do not express any of the ionotropic receptors, yet the ESNs themselves express metabotropic receptors. Thus, we speculate that their production of glutamate may be for communication with neighboring ESNs, rather than to their interneuron targets.
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Affiliation(s)
- Cezar Borba
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Barbara, California 93106
| | - Matthew J Kourakis
- Neuroscience Research Institute, University of California, Santa Barbara, California 93106
| | - Yishen Miao
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Barbara, California 93106
| | - Bharath Guduri
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Barbara, California 93106
| | - Jianan Deng
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Barbara, California 93106
| | - William C Smith
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Barbara, California 93106
- Neuroscience Research Institute, University of California, Santa Barbara, California 93106
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2
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Dai Y, Zhong Y, Pan R, Yuan L, Fu Y, Chen Y, Du J, Li M, Wang X, Liu H, Shi C, Liu G, Zhu P, Shimeld S, Zhou X, Li G. Evolutionary origin of the chordate nervous system revealed by amphioxus developmental trajectories. Nat Ecol Evol 2024; 8:1693-1710. [PMID: 39025981 DOI: 10.1038/s41559-024-02469-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 06/17/2024] [Indexed: 07/20/2024]
Abstract
The common ancestor of all vertebrates had a highly sophisticated nervous system, but questions remain about the evolution of vertebrate neural cell types. The amphioxus, a chordate that diverged before the origin of vertebrates, can inform vertebrate evolution. Here we develop and analyse a single-cell RNA-sequencing dataset from seven amphioxus embryo stages to understand chordate cell type evolution and to study vertebrate neural cell type origins. We identified many new amphioxus cell types, including homologues to the vertebrate hypothalamus and neurohypophysis, rooting the evolutionary origin of these structures. On the basis of ancestor-descendant reconstruction of cell trajectories of the amphioxus and other species, we inferred expression dynamics of transcription factor genes throughout embryogenesis and identified three ancient developmental routes forming chordate neurons. We characterized cell specification at the mechanistic level and generated mutant lines to examine the function of five key transcription factors involved in neural specification. Our results show three developmental origins for the vertebrate nervous system: an anterior FoxQ2-dependent mechanism that is deeply conserved in invertebrates, a less-conserved route leading to more posterior neurons in the vertebrate spinal cord and a mechanism for specifying neuromesoderm progenitors that is restricted to chordates. The evolution of neuromesoderm progenitors may have led to a dramatic shift in posterior neural and mesodermal cell fate decisions and the body elongation process in a stem chordate.
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Affiliation(s)
- Yichen Dai
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, China
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Beijing, China
| | - Yanhong Zhong
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, China
| | - Rongrong Pan
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, China
| | - Liang Yuan
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, China
- School of Life Sciences, Xinjiang Normal University, Urumqi, China
| | - Yongheng Fu
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, China
| | - Yuwei Chen
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, China
| | - Juan Du
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Beijing, China
| | - Meng Li
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Beijing, China
| | - Xiao Wang
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Beijing, China
| | - Huimin Liu
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, China
| | - Chenggang Shi
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, China
| | - Gaoming Liu
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Beijing, China
| | - Pingfen Zhu
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Beijing, China
| | | | - Xuming Zhou
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Beijing, China.
| | - Guang Li
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, China.
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3
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Gigante ED, Piekarz KM, Gurgis A, Cohen L, Razy-Krajka F, Popsuj S, Johnson CJ, Ali HS, Mohana Sundaram S, Stolfi A. Specification and survival of post-metamorphic branchiomeric neurons in a non-vertebrate chordate. Development 2024; 151:dev202719. [PMID: 38895900 PMCID: PMC11273300 DOI: 10.1242/dev.202719] [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: 01/22/2024] [Accepted: 06/10/2024] [Indexed: 06/21/2024]
Abstract
Tunicates are the sister group to the vertebrates, yet most species have a life cycle split between swimming larva and sedentary adult phases. During metamorphosis, larval neurons are replaced by adult-specific ones. The regulatory mechanisms underlying this replacement remain largely unknown. Using tissue-specific CRISPR/Cas9-mediated mutagenesis in the tunicate Ciona, we show that orthologs of conserved hindbrain and branchiomeric neuron regulatory factors Pax2/5/8 and Phox2 are required to specify the 'neck', a cellular compartment set aside in the larva to give rise to cranial motor neuron-like neurons post-metamorphosis. Using bulk and single-cell RNA-sequencing analyses, we characterize the transcriptome of the neck downstream of Pax2/5/8. We present evidence that neck-derived adult ciliomotor neurons begin to differentiate in the larva and persist through metamorphosis, contrary to the assumption that the adult nervous system is formed after settlement and the death of larval neurons during metamorphosis. Finally, we show that FGF signaling during the larval phase alters the patterning of the neck and its derivatives. Suppression of FGF converts neck cells into larval neurons that fail to survive metamorphosis, whereas prolonged FGF signaling promotes an adult neural stem cell-like fate.
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Affiliation(s)
- Eduardo D. Gigante
- School of Biological Sciences, College of Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Katarzyna M. Piekarz
- School of Biological Sciences, College of Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Alexandra Gurgis
- School of Biological Sciences, College of Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
- Department of Biology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Leslie Cohen
- School of Biological Sciences, College of Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Florian Razy-Krajka
- School of Biological Sciences, College of Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Sydney Popsuj
- School of Biological Sciences, College of Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Christopher J. Johnson
- School of Biological Sciences, College of Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Hussan S. Ali
- School of Biological Sciences, College of Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Shruthi Mohana Sundaram
- School of Biological Sciences, College of Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Alberto Stolfi
- School of Biological Sciences, College of Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
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4
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Popsuj S, Cohen L, Ward S, Lewis A, Yoshida S, Herrera RA, Cota CD, Stolfi A. CRISPR/Cas9 protocols for disrupting gene function in the non-vertebrate chordate Ciona. Integr Comp Biol 2024:icae108. [PMID: 38982335 DOI: 10.1093/icb/icae108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/11/2024] Open
Abstract
The evolutionary origins of chordates and their diversification into the three major subphyla of tunicates, vertebrates, and cephalochordates pose myriad questions about the genetic and developmental mechanisms underlying this radiation. Studies in non-vertebrate chordates have refined our model of what the ancestral chordate may have looked like, and have revealed the pre-vertebrate origins of key cellular and developmental traits. Work in the major tunicate laboratory model Ciona has benefitted greatly from the emergence of CRISPR/Cas9 techniques for targeted gene disruption. Here we review some of the important findings made possible by CRISPR in Ciona, and present our latest protocols and recommended practices for plasmid-based, tissue-specific CRISPR/Cas9-mediated mutagenesis.
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Affiliation(s)
- Sydney Popsuj
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Lindsey Cohen
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Sydney Ward
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
- Agnes Scott College, Decatur, GA, 30030, USA
| | - Arabella Lewis
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
- Agnes Scott College, Decatur, GA, 30030, USA
| | | | | | | | - Alberto Stolfi
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
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Kourakis MJ, Ryan K, Newman-Smith ED, Meinertzhagen IA, Smith WC. Deep homologies in chordate caudal central nervous systems. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.03.597227. [PMID: 38895365 PMCID: PMC11185728 DOI: 10.1101/2024.06.03.597227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
Invertebrate chordates, such as the tunicate Ciona, can offer insight into the evolution of the chordate phylum. Anatomical features that are shared between invertebrate chordates and vertebrates may be taken as evidence of their presence in a common chordate ancestor. The central nervous systems of Ciona larvae and vertebrates share a similar anatomy despite the Ciona CNS having ~180 neurons. However, the depth of conservation between the Ciona CNS and those in vertebrates is not resolved. The Ciona caudal CNS, while appearing spinal cord-like, has hitherto been thought to lack motor neurons, bringing into question its homology with the vertebrate spinal cord. We show here that the Ciona larval caudal CNS does, in fact, have functional motor neurons along its length, pointing to the presence of a spinal cord-like structure at the base of the chordates. We extend our analysis of shared CNS anatomy further to explore the Ciona "motor ganglion", which has been proposed to be a homolog of the vertebrate hindbrain, spinal cord, or both. We find that a cluster of neurons in the dorsal motor ganglion shares anatomical location, developmental pathway, neural circuit architecture, and gene expression with the vertebrate cerebellum. However, functionally, the Ciona cluster appears to have more in common with vertebrate cerebellum-like structures, insofar as it receives and processes direct sensory input. These findings are consistent with earlier speculation that the cerebellum evolved from a cerebellum-like structure, and suggest that the latter structure was present in the dorsal hindbrain of a common chordate ancestor.
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Affiliation(s)
- Matthew J Kourakis
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA, USA 93106
| | - Kerrianne Ryan
- Life Sciences Centre, Dalhousie University, Halifax, NS, Canada B3H 1A5
| | - Erin D Newman-Smith
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA, USA 93106
| | | | - William C Smith
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA, USA 93106
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, USA 93106
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6
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Spalek K, Straathof M, Koyuncu L, Grydeland H, van der Geest A, Van't Hof SR, Crone EA, Barba-Müller E, Carmona S, Denys D, Tamnes CK, Burke S, Hoekzema E. Pregnancy renders anatomical changes in hypothalamic substructures of the human brain that relate to aspects of maternal behavior. Psychoneuroendocrinology 2024; 164:107021. [PMID: 38492349 DOI: 10.1016/j.psyneuen.2024.107021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 03/07/2024] [Accepted: 03/09/2024] [Indexed: 03/18/2024]
Abstract
Animal studies have shown that pregnancy is associated with neural adaptations that promote maternal care. The hypothalamus represents a central structure of the mammalian maternal brain and hormonal priming of specific hypothalamic nuclei plays a key role in the induction and expression of maternal behavior. In humans, we have previously demonstrated that becoming a mother involves changes in grey matter anatomy, primarily in association areas of the cerebral cortex. In the current study, we investigated whether pregnancy renders anatomical changes in the hypothalamus. Using an advanced delineation technique, five hypothalamic substructures were defined in longitudinal MRI scans of 107 women extracted from two prospective pre-conception cohort studies, including 50 women who were scanned before and after pregnancy and 57 nulliparous control women scanned at a similar time interval. We showed that becoming a mother is associated with volume reductions in the anterior-superior, superior tuberal and posterior hypothalamus. In addition, these structural changes related to hormonal levels during pregnancy and specific aspects of self-reported maternal behavior in late pregnancy, including maternal-fetal attachment and nesting behavior. These findings show that pregnancy leads to changes in hypothalamic anatomy and suggest that these contribute to the development of maternal behavior in humans, supporting the conservation of key aspects of maternal brain circuitry and their role in maternal behavior across species.
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Affiliation(s)
- Klara Spalek
- Hoekzema Lab, Amsterdam University Medical Center (Amsterdam UMC), location University of Amsterdam, Department of Psychiatry, Amsterdam Neuroscience, Amsterdam Reproduction and Development, Amsterdam, the Netherlands
| | - Milou Straathof
- Hoekzema Lab, Amsterdam University Medical Center (Amsterdam UMC), location University of Amsterdam, Department of Psychiatry, Amsterdam Neuroscience, Amsterdam Reproduction and Development, Amsterdam, the Netherlands
| | - Lal Koyuncu
- Brain and Development Research Center, Leiden Institute for Brain and Cognition, Leiden University, Leiden, the Netherlands
| | - Håkon Grydeland
- Center for Lifespan Changes in Brain and Cognition (LCBC), Department of Psychology, University of Oslo, Norway
| | - Anouk van der Geest
- Brain and Development Research Center, Leiden Institute for Brain and Cognition, Leiden University, Leiden, the Netherlands
| | - Sophie R Van't Hof
- Hoekzema Lab, Amsterdam University Medical Center (Amsterdam UMC), location University of Amsterdam, Department of Psychiatry, Amsterdam Neuroscience, Amsterdam Reproduction and Development, Amsterdam, the Netherlands
| | - Eveline A Crone
- Brain and Development Research Center, Leiden Institute for Brain and Cognition, Leiden University, Leiden, the Netherlands
| | | | - Susana Carmona
- Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Madrid, Spain
| | - Damiaan Denys
- Department of Psychiatry, Amsterdam University Medical Center (Amsterdam UMC), location University of Amsterdam, the Netherlands
| | - Christian K Tamnes
- PROMENTA Research Center, Department of Psychology, University of Oslo, Oslo, Norway; NORMENT, Institute of Clinical Medicine, University of Oslo, Oslo, Norway; Department of Psychiatric Research, Diakonhjemmet Hospital, Oslo, Norway
| | - Sarah Burke
- Brain and Development Research Center, Leiden Institute for Brain and Cognition, Leiden University, Leiden, the Netherlands; Interdisciplinary Center Psychopathology and Emotion regulation, Department of Psychiatry, University Medical Center Groningen, University of Groningen, the Netherlands
| | - Elseline Hoekzema
- Hoekzema Lab, Amsterdam University Medical Center (Amsterdam UMC), location University of Amsterdam, Department of Psychiatry, Amsterdam Neuroscience, Amsterdam Reproduction and Development, Amsterdam, the Netherlands.
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7
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Kiran NS, Yashaswini C, Chatterjee A. Zebrafish: A trending model for gut-brain axis investigation. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2024; 270:106902. [PMID: 38537435 DOI: 10.1016/j.aquatox.2024.106902] [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: 02/05/2024] [Revised: 03/04/2024] [Accepted: 03/13/2024] [Indexed: 04/13/2024]
Abstract
Zebrafish (Danio rerio) has ascended as a pivotal model organism in the realm of gut-brain axis research, principally owing to its high-throughput experimental capabilities and evolutionary alignment with mammals. The inherent transparency of zebrafish embryos facilitates unprecedented real-time imaging, affording unparalleled insights into the intricate dynamics of bidirectional communication between the gut and the brain. Noteworthy are the structural and functional parallels shared between the zebrafish and mammalian gut-brain axis components, rendering zebrafish an invaluable model for probing the molecular and cellular intricacies inherent in this critical physiological interaction. Recent investigations in zebrafish have systematically explored the impact of gut microbiota on neurodevelopment, behaviour, and disease susceptibility, underscoring the model's prowess in unravelling the multifaceted influence of microbial communities in shaping gut-brain interactions. Leveraging the genetic manipulability inherent in zebrafish, researchers have embarked on targeted explorations of specific pathways and molecular mechanisms, providing nuanced insights into the fundamental functioning of the gut-brain axis. This comprehensive review synthesizes pivotal findings and methodological advancements derived from zebrafish-based gut-brain axis research, accentuating the model's potential to significantly advance our understanding of this complex interplay. Furthermore, it underscores the translational significance of these insights, offering promising avenues for the identification of therapeutic targets in neuro-gastroenterological disorders and psychiatric conditions intricately linked with gut-brain interactions.
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Affiliation(s)
- Neelakanta Sarvashiva Kiran
- Department of Biotechnology, School of Applied Sciences, REVA University, Kattigenahalli, Yelahanka, Bengaluru, 560064, Karnataka, India
| | - Chandrashekar Yashaswini
- Department of Biotechnology, School of Applied Sciences, REVA University, Kattigenahalli, Yelahanka, Bengaluru, 560064, Karnataka, India
| | - Ankita Chatterjee
- Department of Biotechnology, School of Applied Sciences, REVA University, Kattigenahalli, Yelahanka, Bengaluru, 560064, Karnataka, India.
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Frese AN, Mariossi A, Levine MS, Wühr M. Quantitative proteome dynamics across embryogenesis in a model chordate. iScience 2024; 27:109355. [PMID: 38510129 PMCID: PMC10951915 DOI: 10.1016/j.isci.2024.109355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 12/11/2023] [Accepted: 02/23/2024] [Indexed: 03/22/2024] Open
Abstract
The evolution of gene expression programs underlying the development of vertebrates remains poorly characterized. Here, we present a comprehensive proteome atlas of the model chordate Ciona, covering eight developmental stages and ∼7,000 translated genes, accompanied by a multi-omics analysis of co-evolution with the vertebrate Xenopus. Quantitative proteome comparisons argue against the widely held hourglass model, based solely on transcriptomic profiles, whereby peak conservation is observed during mid-developmental stages. Our analysis reveals maximal divergence at these stages, particularly gastrulation and neurulation. Together, our work provides a valuable resource for evaluating conservation and divergence of multi-omics profiles underlying the diversification of vertebrates.
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Affiliation(s)
- Alexander N. Frese
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Andrea Mariossi
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Michael S. Levine
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Martin Wühr
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
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9
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Beaulieu M. Capturing wild animal welfare: a physiological perspective. Biol Rev Camb Philos Soc 2024; 99:1-22. [PMID: 37635128 DOI: 10.1111/brv.13009] [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: 03/07/2023] [Revised: 08/07/2023] [Accepted: 08/07/2023] [Indexed: 08/29/2023]
Abstract
Affective states, such as emotions, are presumably widespread across the animal kingdom because of the adaptive advantages they are supposed to confer. However, the study of the affective states of animals has thus far been largely restricted to enhancing the welfare of animals managed by humans in non-natural contexts. Given the diversity of wild animals and the variable conditions they can experience, extending studies on animal affective states to the natural conditions that most animals experience will allow us to broaden and deepen our general understanding of animal welfare. Yet, this same diversity makes examining animal welfare in the wild highly challenging. There is therefore a need for unifying theoretical frameworks and methodological approaches that can guide researchers keen to engage in this promising research area. The aim of this article is to help advance this important research area by highlighting the central relationship between physiology and animal welfare and rectify its apparent oversight, as revealed by the current scientific literature on wild animals. Moreover, this article emphasises the advantages of including physiological markers to assess animal welfare in the wild (e.g. objectivity, comparability, condition range, temporality), as well as their concomitant limitations (e.g. only access to peripheral physiological markers with complex relationships with affective states). Best-practice recommendations (e.g. replication and multifactorial approaches) are also provided to allow physiological markers to be used most effectively and appropriately when assessing the welfare of animals in their natural habitat. This review seeks to provide the foundation for a new and distinct research area with a vast theoretical and applied potential: wild animal welfare physiology.
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Affiliation(s)
- Michaël Beaulieu
- Wild Animal Initiative, 5123 W 98th St, 1204, Minneapolis, MN, 55437, USA
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10
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Fong H, Zheng J, Kurrasch D. The structural and functional complexity of the integrative hypothalamus. Science 2023; 382:388-394. [PMID: 37883552 DOI: 10.1126/science.adh8488] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Accepted: 09/28/2023] [Indexed: 10/28/2023]
Abstract
The hypothalamus ("hypo" meaning below, and "thalamus" meaning bed) consists of regulatory circuits that support basic life functions that ensure survival. Sitting at the interface between peripheral, environmental, and neural inputs, the hypothalamus integrates these sensory inputs to influence a range of physiologies and behaviors. Unlike the neocortex, in which a stereotyped cytoarchitecture mediates complex functions across a comparatively small number of neuronal fates, the hypothalamus comprises upwards of thousands of distinct cell types that form redundant yet functionally discrete circuits. With single-cell RNA sequencing studies revealing further cellular heterogeneity and modern photonic tools enabling high-resolution dissection of complex circuitry, a new era of hypothalamic mapping has begun. Here, we provide a general overview of mammalian hypothalamic organization, development, and connectivity to help welcome newcomers into this exciting field.
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Affiliation(s)
- Harmony Fong
- Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AB, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
| | - Jing Zheng
- Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AB, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
| | - Deborah Kurrasch
- Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AB, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
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11
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Long J, Mariossi A, Cao C, Mo Z, Thompson JW, Levine MS, Lemaire LA. Cereblon influences the timing of muscle differentiation in Ciona tadpoles. Proc Natl Acad Sci U S A 2023; 120:e2309989120. [PMID: 37856545 PMCID: PMC10614628 DOI: 10.1073/pnas.2309989120] [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: 06/14/2023] [Accepted: 09/09/2023] [Indexed: 10/21/2023] Open
Abstract
Thalidomide has a dark history as a teratogen, but in recent years, its derivates have been shown to function as potent chemotherapeutic agents. These drugs bind cereblon (CRBN), the substrate receptor of an E3 ubiquitin ligase complex, and modify its degradation targets. Despite these insights, remarkably little is known about the normal function of cereblon in development. Here, we employ Ciona, a simple invertebrate chordate, to identify endogenous Crbn targets. In Ciona, Crbn is specifically expressed in developing muscles during tail elongation before they acquire contractile activity. Crbn expression is activated by Mrf, the ortholog of MYOD1, a transcription factor important for muscle differentiation. CRISPR/Cas9-mediated mutations of Crbn lead to precocious onset of muscle contractions. By contrast, overexpression of Crbn delays contractions and is associated with decreased expression of contractile protein genes such as troponin. This reduction is possibly due to reduced Mrf protein levels without altering Mrf mRNA levels. Our findings suggest that Mrf and Crbn form a negative feedback loop to control the precision of muscle differentiation during tail elongation.
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Affiliation(s)
- Juanjuan Long
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ08544
| | - Andrea Mariossi
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ08544
| | - Chen Cao
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ08544
| | | | | | - Michael S. Levine
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ08544
- Department of Molecular Biology, Princeton University, Princeton, NJ08544
| | - Laurence A. Lemaire
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ08544
- Department of Biology, Saint Louis University, St. Louis, MO63103
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12
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Andrade López JM, Pani AM, Wu M, Gerhart J, Lowe CJ. Molecular characterization of nervous system organization in the hemichordate acorn worm Saccoglossus kowalevskii. PLoS Biol 2023; 21:e3002242. [PMID: 37725784 PMCID: PMC10508912 DOI: 10.1371/journal.pbio.3002242] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 07/11/2023] [Indexed: 09/21/2023] Open
Abstract
Hemichordates are an important group for investigating the evolution of bilaterian nervous systems. As the closest chordate outgroup with a bilaterally symmetric adult body plan, hemichordates are particularly informative for exploring the origins of chordates. Despite the importance of hemichordate neuroanatomy for testing hypotheses on deuterostome and chordate evolution, adult hemichordate nervous systems have not been comprehensively described using molecular techniques, and classic histological descriptions disagree on basic aspects of nervous system organization. A molecular description of hemichordate nervous system organization is important for both anatomical comparisons across phyla and for attempts to understand how conserved gene regulatory programs for ectodermal patterning relate to morphological evolution in deep time. Here, we describe the basic organization of the adult hemichordate Saccoglossus kowalevskii nervous system using immunofluorescence, in situ hybridization, and transgenic reporters to visualize neurons, neuropil, and key neuronal cell types. Consistent with previous descriptions, we found the S. kowalevskii nervous system consists of a pervasive nerve plexus concentrated in the anterior, along with nerve cords on both the dorsal and ventral side. Neuronal cell types exhibited clear anteroposterior and dorsoventral regionalization in multiple areas of the body. We observed spatially demarcated expression patterns for many genes involved in synthesis or transport of neurotransmitters and neuropeptides but did not observe clear distinctions between putatively centralized and decentralized portions of the nervous system. The plexus shows regionalized structure and is consistent with the proboscis base as a major site for information processing rather than the dorsal nerve cord. In the trunk, there is a clear division of cell types between the dorsal and ventral cords, suggesting differences in function. The absence of neural processes crossing the basement membrane into muscle and extensive axonal varicosities suggest that volume transmission may play an important role in neural function. These data now facilitate more informed neural comparisons between hemichordates and other groups, contributing to broader debates on the origins and evolution of bilaterian nervous systems.
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Affiliation(s)
- José M. Andrade López
- Department of Biology, Stanford University, Stanford, California, United States of America
| | - Ariel M. Pani
- Departments of Biology and Cell Biology, University of Virginia, Charlottesville, Virginia, Unites States of America
| | - Mike Wu
- Department of Molecular and Cell Biology, University of California, Berkeley, California, Unites States of America
| | - John Gerhart
- Department of Molecular and Cell Biology, University of California, Berkeley, California, Unites States of America
| | - Christopher J. Lowe
- Department of Biology, Stanford University, Stanford, California, United States of America
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13
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Chung J, Newman-Smith E, Kourakis MJ, Miao Y, Borba C, Medina J, Laurent T, Gallean B, Faure E, Smith WC. A single oscillating proto-hypothalamic neuron gates taxis behavior in the primitive chordate Ciona. Curr Biol 2023; 33:3360-3370.e4. [PMID: 37490920 PMCID: PMC10528541 DOI: 10.1016/j.cub.2023.06.080] [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: 04/21/2023] [Revised: 06/05/2023] [Accepted: 06/29/2023] [Indexed: 07/27/2023]
Abstract
Ciona larvae display a number of behaviors, including negative phototaxis. In negative phototaxis, the larvae first perform short spontaneous rhythmic casting swims. As larvae are cast in a light field, their photoreceptors are directionally shaded by an associated pigment cell, providing a phototactic cue. This then evokes an extended negative taxis swim. We report here that the larval forebrain of Ciona has a previously uncharacterized single slow-oscillating inhibitory neuron (neuron cor-assBVIN78) that projects to the midbrain, where it targets key interneurons of the phototaxis circuit known as the photoreceptor relay neurons. The anatomical location, gene expression, and oscillation of cor-assBVIN78 suggest homology to oscillating neurons of the vertebrate hypothalamus. Ablation of cor-assBVIN78 results in larvae showing extended phototaxis-like swims, even in the absence of phototactic cues. These results indicate that cor-assBVIN78 has a gating activity on phototaxis by projecting temporally oscillating inhibition to the photoreceptor relay neurons. However, in intact larvae, the frequency of cor-assBVIN78 oscillation does not match that of the rhythmic spontaneous swims, indicating that the troughs in oscillations do not themselves initiate swims but rather that cor-assBVIN78 may modulate the phototaxis circuit by filtering out low-level inputs while restricting them temporally to the troughs in inhibition.
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Affiliation(s)
- Janeva Chung
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Erin Newman-Smith
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Matthew J Kourakis
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Yishen Miao
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Cezar Borba
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Juan Medina
- College of Creative Studies, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Tao Laurent
- Laboratoire d'Informatique, de Robotique et de Microélectronique de Montpellier, Université de Montpellier, CNRS, Montpellier, France
| | - Benjamin Gallean
- Centre de Recherche de Biologie cellulaire de Montpellier, Université de Montpellier, CNRS, Montpellier, France
| | - Emmanuel Faure
- Laboratoire d'Informatique, de Robotique et de Microélectronique de Montpellier, Université de Montpellier, CNRS, Montpellier, France
| | - William C Smith
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA; Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
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14
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Gigante ED, Piekarz KM, Gurgis A, Cohen L, Razy-Krajka F, Popsuj S, Ali HS, Sundaram SM, Stolfi A. Specification and survival of post-metamorphic branchiomeric neurons in the hindbrain of a non-vertebrate chordate. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.16.545305. [PMID: 37645866 PMCID: PMC10461979 DOI: 10.1101/2023.06.16.545305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Tunicates are the sister group to the vertebrates, yet most species have a life cycle split between swimming larva and sedentary adult phases. During metamorphosis, larval neurons are largely replaced by adult-specific ones. Yet the regulatory mechanisms underlying this neural replacement remain largely unknown. Using tissue-specific CRISPR/Cas9-mediated mutagenesis in the tunicate Ciona, we show that orthologs of conserved hindbrain and branchiomeric neuron regulatory factors Pax2/5/8 and Phox2 are required to specify the "Neck", a compartment of cells set aside in the larva to give rise to cranial motor neuron-like neurons in the adult. Using bulk and single-cell RNAseq analyses, we also characterize the transcriptome of the Neck downstream of Pax2/5/8. Surprisingly, we find that Neck-derived adult ciliomotor neurons begin to differentiate in the larva, contrary to the long-held assumption that the adult nervous system is formed only after settlement and the death of larval neurons during metamorphosis. Finally, we show that manipulating FGF signaling during the larval phase alters the patterning of the Neck and its derivatives. Suppression of FGF converts Neck cells into larval neurons that fail to survive metamorphosis, while prolonged FGF signaling promotes an adult neural stem cell-like fate instead.
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Affiliation(s)
- Eduardo D Gigante
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, 30332; USA
| | - Katarzyna M Piekarz
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, 30332; USA
| | - Alexandra Gurgis
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, 30332; USA
- Department of Biology, Case Western Reserve University, Cleveland, OH, 44106; USA
| | - Leslie Cohen
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, 30332; USA
| | - Florian Razy-Krajka
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, 30332; USA
| | - Sydney Popsuj
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, 30332; USA
| | - Hussan S Ali
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, 30332; USA
| | | | - Alberto Stolfi
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, 30332; USA
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15
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Chung J, Newman-Smith E, Kourakis MJ, Miao Y, Borba C, Medina J, Laurent T, Gallean B, Faure E, Smith WC. A single oscillating proto-hypothalamic neuron gates taxis behavior in the primitive chordate Ciona. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.24.538092. [PMID: 37162881 PMCID: PMC10168268 DOI: 10.1101/2023.04.24.538092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Ciona larvae display a number of behaviors, including negative phototaxis. In negative phototaxis, the larvae first perform short spontaneous rhythmic casting swims. As larvae cast in a light field, their photoreceptors are directionally shaded by an associated pigment cell, providing a phototactic cue. This then evokes an extended negative taxis swim. We report here that the larval forebrain of Ciona has a previously uncharacterized single slow-oscillating inhibitory neuron (neuron cor-assBVIN78 ) that projects to the midbrain, where it targets key interneurons of the phototaxis circuit known as the photoreceptor relay neurons . The anatomical location, gene expression and oscillation of cor-assBVIN78 suggest homology to oscillating neurons of the vertebrate hypothalamus. Ablation of cor-assBVIN78 results in larvae showing extended phototaxis-like swims, but which occur in the absence of phototactic cues. These results indicate that cor-assBVIN78 has a gating activity on phototaxis by projecting temporally-oscillating inhibition to the photoreceptor relay neurons. However, in intact larvae the frequency of cor-assBVIN78 oscillation does not match that of the rhythmic spontaneous swims, indicating that the troughs in oscillations do not themselves initiate swims, but rather that cor-assBVIN78 may modulate the phototaxis circuit by filtering out low level inputs while restricting them temporally to the troughs in inhibition.
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Affiliation(s)
- Janeva Chung
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, USA 93106
| | - Erin Newman-Smith
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA, USA 93106
| | - Matthew J. Kourakis
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA, USA 93106
| | - Yishen Miao
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, USA 93106
| | - Cezar Borba
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, USA 93106
| | - Juan Medina
- College of Creative Studies, University of California Santa Barbara, Santa Barbara, CA, USA 93106
| | - Tao Laurent
- Laboratoire d’Informatique, de Robotique et de Microélectronique de Montpellier, Université de Montpellier,CNRS, Montpellier, France
| | - Benjamin Gallean
- Centre de Recherche de Biologie cellulaire de Montpellier, Université de Montpellier, CNRS, Montpellier, France
| | - Emmanuel Faure
- Laboratoire d’Informatique, de Robotique et de Microélectronique de Montpellier, Université de Montpellier,CNRS, Montpellier, France
| | - William C Smith
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, USA 93106
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA, USA 93106
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16
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Athira A, Dondorp D, Rudolf J, Peytral O, Chatzigeorgiou M. Comprehensive analysis of locomotion dynamics in the protochordate Ciona intestinalis reveals how neuromodulators flexibly shape its behavioral repertoire. PLoS Biol 2022; 20:e3001744. [PMID: 35925898 PMCID: PMC9352054 DOI: 10.1371/journal.pbio.3001744] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 07/06/2022] [Indexed: 11/19/2022] Open
Abstract
Vertebrate nervous systems can generate a remarkable diversity of behaviors. However, our understanding of how behaviors may have evolved in the chordate lineage is limited by the lack of neuroethological studies leveraging our closest invertebrate relatives. Here, we combine high-throughput video acquisition with pharmacological perturbations of bioamine signaling to systematically reveal the global structure of the motor behavioral repertoire in the Ciona intestinalis larvae. Most of Ciona’s postural variance can be captured by 6 basic shapes, which we term “eigencionas.” Motif analysis of postural time series revealed numerous stereotyped behavioral maneuvers including “startle-like” and “beat-and-glide.” Employing computational modeling of swimming dynamics and spatiotemporal embedding of postural features revealed that behavioral differences are generated at the levels of motor modules and the transitions between, which may in part be modulated by bioamines. Finally, we show that flexible motor module usage gives rise to diverse behaviors in response to different light stimuli. Vertebrate nervous systems can generate a remarkable diversity of behaviors, but how did these evolve in the chordate lineage? A study of the protochordate Ciona intestinalis reveals novel insights into how a simple chordate brain uses neuromodulators to control its behavioral repertoire.
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Affiliation(s)
- Athira Athira
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Daniel Dondorp
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Jerneja Rudolf
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Olivia Peytral
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Marios Chatzigeorgiou
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
- * E-mail:
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17
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Shaffer C, Westlin C, Quigley KS, Whitfield-Gabrieli S, Barrett LF. Allostasis, Action, and Affect in Depression: Insights from the Theory of Constructed Emotion. Annu Rev Clin Psychol 2022; 18:553-580. [PMID: 35534123 PMCID: PMC9247744 DOI: 10.1146/annurev-clinpsy-081219-115627] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The theory of constructed emotion is a systems neuroscience approach to understanding the nature of emotion. It is also a general theoretical framework to guide hypothesis generation for how actions and experiences are constructed as the brain continually anticipates metabolic needs and attempts to meet those needs before they arise (termed allostasis). In this review, we introduce this framework and hypothesize that allostatic dysregulation is a trans-disorder vulnerability for mental and physical illness. We then review published findings consistent with the hypothesis that several symptoms in major depressive disorder (MDD), such as fatigue, distress, context insensitivity, reward insensitivity, and motor retardation, are associated with persistent problems in energy regulation. Our approach transforms the current understanding of MDD as resulting from enhanced emotional reactivity combined with reduced cognitive control and, in doing so, offers novel hypotheses regarding the development, progression, treatment, and prevention of MDD.
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Affiliation(s)
- Clare Shaffer
- Department of Psychology, Northeastern University, Boston, Massachusetts, USA; ,
| | - Christiana Westlin
- Department of Psychology, Northeastern University, Boston, Massachusetts, USA; ,
| | - Karen S Quigley
- Department of Psychology, Northeastern University, Boston, Massachusetts, USA; ,
- VA Bedford Healthcare System, Bedford, Massachusetts, USA
| | - Susan Whitfield-Gabrieli
- Department of Psychology, Northeastern University, Boston, Massachusetts, USA; ,
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Lisa Feldman Barrett
- Department of Psychology, Northeastern University, Boston, Massachusetts, USA; ,
- Department of Psychiatry and the Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, USA
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18
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Neuronal identities derived by misexpression of the POU IV sensory determinant in a protovertebrate. Proc Natl Acad Sci U S A 2022; 119:2118817119. [PMID: 35042818 PMCID: PMC8794889 DOI: 10.1073/pnas.2118817119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/04/2021] [Indexed: 12/13/2022] Open
Abstract
The protovertebrate Ciona intestinalis is an ideal system to investigate both gene regulatory networks that underlie cell-type specification and how cell types have evolved. In this study, we use single-cell technology, experimental manipulations, and computational analyses to understand the role of the regulatory determinant POU IV—a homolog of Brn3 in vertebrates—in specifying various sensory cell types in Ciona. Surprisingly, the misexpression of POU IV throughout the epidermis led to the formation of hybrid sensory cell types, including those exhibiting properties of both palp sensory cells and bipolar tail neurons. These results demonstrate the interconnectedness of diverse sensory specification networks and give insights into the opportunities and challenges of reprogramming cell types through the targeted misexpression of cellular determinants. The protovertebrate Ciona intestinalis type A (sometimes called Ciona robusta) contains a series of sensory cell types distributed across the head–tail axis of swimming tadpoles. They arise from lateral regions of the neural plate that exhibit properties of vertebrate placodes and neural crest. The sensory determinant POU IV/Brn3 is known to work in concert with regional determinants, such as Foxg and Neurogenin, to produce palp sensory cells (PSCs) and bipolar tail neurons (BTNs), in head and tail regions, respectively. A combination of single-cell RNA-sequencing (scRNA-seq) assays, computational analysis, and experimental manipulations suggests that misexpression of POU IV results in variable transformations of epidermal cells into hybrid sensory cell types, including those exhibiting properties of both PSCs and BTNs. Hybrid properties are due to coexpression of Foxg and Neurogenin that is triggered by an unexpected POU IV feedback loop. Hybrid cells were also found to express a synthetic gene battery that is not coexpressed in any known cell type. We discuss these results with respect to the opportunities and challenges of reprogramming cell types through the targeted misexpression of cellular determinants.
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