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Obukhova AL, Khabarova MY, Semenova MN, Starunov VV, Voronezhskaya EE, Ivashkin EG. Spontaneous intersibling polymorphism in the development of dopaminergic neuroendocrine cells in sea urchin larvae: impacts on the expansion of marine benthic species. Front Neurosci 2024; 18:1348999. [PMID: 38660226 PMCID: PMC11039814 DOI: 10.3389/fnins.2024.1348999] [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: 12/03/2023] [Accepted: 03/27/2024] [Indexed: 04/26/2024] Open
Abstract
Introduction The plasticity of the nervous system plays a crucial role in shaping adaptive neural circuits and corresponding animal behaviors. Understanding the mechanisms underlying neural plasticity during development and its implications for animal adaptation constitutes an intriguing area of research. Sea urchin larvae offer a fascinating subject for investigation due to their remarkable evolutionary and ecological diversity, as well as their diverse developmental forms and behavioral patterns. Materials and methods We conducted immunochemical and histochemical analyses of serotonin-containing (5-HT-neurons) and dopamine-containing (DA-positive) neurons to study their developmental dynamics in two sea urchin species: Mesocentrotus nudus and Paracentrotus lividus. Our approach involved detailed visualization of 5-HT- and DA-positive neurons at gastrula-pluteus stages, coupled with behavioral assays to assess larval upward and downward swimming in the water column, with a focus on correlating cell numbers with larval swimming ability. Results The study reveals a heterochronic polymorphism in the appearance of post-oral DA-positive neuroendocrine cells and confirms the stable differentiation pattern of apical 5-HT neurons in larvae of both species. Notably, larvae of the same age exhibit a two- to four-fold difference in DA neurons. An increased number of DA neurons and application of dopamine positively correlate with larval downward swimming, whereas 5-HT-neurons and serotonin application induce upward swimming. The ratio of 5-HT/DA neurons determines the stage-dependent vertical distribution of larvae within the water column. Consequently, larvae from the same generation with a higher number of DA-positive neurons tend to remain at the bottom compared to those with fewer DA-positive neurons. Discussion The proportion of 5-HT and DA neurons within larvae of the same age underlies the different potentials of individuals for upward and downward swimming. A proposed model illustrates how coordination in humoral regulation, based on heterochrony in DA-positive neuroendocrine cell differentiation, influences larval behavior, mitigates competition between siblings, and ensures optimal population expansion. The study explores the evolutionary and ecological implications of these neuroendocrine adaptations in marine species.
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Affiliation(s)
- Alexandra L. Obukhova
- Koltsov Institute of Developmental Biology, Russian Academy Sciences, Moscow, Russia
| | - Marina Yu. Khabarova
- Koltsov Institute of Developmental Biology, Russian Academy Sciences, Moscow, Russia
| | - Marina N. Semenova
- Koltsov Institute of Developmental Biology, Russian Academy Sciences, Moscow, Russia
| | - Viktor V. Starunov
- Department of Invertebrate Zoology, St-Petersburg State University, Saint Petersburg, Russia
- Zoological Institute, Russian Academy Sciences, Saint Petersburg, Russia
| | | | - Evgeny G. Ivashkin
- Koltsov Institute of Developmental Biology, Russian Academy Sciences, Moscow, Russia
- Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russia
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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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Kotsyuba E, Dyachuk V. Role of the Neuroendocrine System of Marine Bivalves in Their Response to Hypoxia. Int J Mol Sci 2023; 24:ijms24021202. [PMID: 36674710 PMCID: PMC9865615 DOI: 10.3390/ijms24021202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 12/28/2022] [Accepted: 01/04/2023] [Indexed: 01/11/2023] Open
Abstract
Mollusks comprise one of the largest phylum of marine invertebrates. With their great diversity of species, various degrees of mobility, and specific behavioral strategies, they haveoccupied marine, freshwater, and terrestrial habitats and play key roles in many ecosystems. This success is explained by their exceptional ability to tolerate a wide range of environmental stresses, such as hypoxia. Most marine bivalvemollusksare exposed to frequent short-term variations in oxygen levels in their marine or estuarine habitats. This stressfactor has caused them to develop a wide variety of adaptive strategies during their evolution, enabling to mobilize rapidly a set of behavioral, physiological, biochemical, and molecular defenses that re-establishing oxygen homeostasis. The neuroendocrine system and its related signaling systems play crucial roles in the regulation of various physiological and behavioral processes in mollusks and, hence, can affect hypoxiatolerance. Little effort has been made to identify the neurotransmitters and genes involved in oxygen homeostasis regulation, and the molecular basis of the differences in the regulatory mechanisms of hypoxia resistance in hypoxia-tolerant and hypoxia-sensitive bivalve species. Here, we summarize current knowledge about the involvement of the neuroendocrine system in the hypoxia stress response, and the possible contributions of various signaling molecules to this process. We thusprovide a basis for understanding the molecular mechanisms underlying hypoxic stress in bivalves, also making comparisons with data from related studies on other species.
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Gilbert E, Teeling C, Lebedeva T, Pedersen S, Chrismas N, Genikhovich G, Modepalli V. Molecular and cellular architecture of the larval sensory organ in the cnidarian Nematostella vectensis. Development 2022; 149:276422. [PMID: 36000354 PMCID: PMC9481973 DOI: 10.1242/dev.200833] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 07/18/2022] [Indexed: 11/29/2022]
Abstract
Cnidarians are the only non-bilaterian group to evolve ciliated larvae with an apical sensory organ, which is possibly homologous to the apical organs of bilaterian primary larvae. Here, we generated transcriptomes of the apical tissue in the sea anemone Nematostella vectensis and showed that it has a unique neuronal signature. By integrating previously published larval single-cell data with our apical transcriptomes, we discovered that the apical domain comprises a minimum of six distinct cell types. We show that the apical organ is compartmentalised into apical tuft cells (spot) and larval-specific neurons (ring). Finally, we identify ISX-like (NVE14554), a PRD class homeobox gene specifically expressed in apical tuft cells, as an FGF signalling-dependent transcription factor responsible for the formation of the apical tuft domain via repression of the neural ring fate in apical cells. With this study, we contribute a comparison of the molecular anatomy of apical organs, which must be carried out across phyla to determine whether this crucial larval structure evolved once or multiple times. Summary:ISX-like homeobox gene is an FGF signalling-dependent transcription factor responsible for the formation of the apical tuft in the sea anemone Nematostella vectensis.
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Affiliation(s)
- Eleanor Gilbert
- Marine Biological Association of the UK, The Laboratory 1 , Citadel Hill, Plymouth PL1 2PB , United Kingdom
- School of Biological and Marine Sciences, University of Plymouth 2 , Plymouth, PL4 8AA , UK
| | - Callum Teeling
- Marine Biological Association of the UK, The Laboratory 1 , Citadel Hill, Plymouth PL1 2PB , United Kingdom
- School of Biological and Marine Sciences, University of Plymouth 2 , Plymouth, PL4 8AA , UK
| | - Tatiana Lebedeva
- University of Vienna 3 Department of Neurosciences and Developmental Biology, Faculty of Life Sciences , , Vienna, 1030 , Austria
- Doctoral School of Ecology and Evolution, University of Vienna 4 , Vienna, 1030 , Austria
| | - Siffreya Pedersen
- Marine Biological Association of the UK, The Laboratory 1 , Citadel Hill, Plymouth PL1 2PB , United Kingdom
| | - Nathan Chrismas
- Marine Biological Association of the UK, The Laboratory 1 , Citadel Hill, Plymouth PL1 2PB , United Kingdom
| | - Grigory Genikhovich
- University of Vienna 3 Department of Neurosciences and Developmental Biology, Faculty of Life Sciences , , Vienna, 1030 , Austria
| | - Vengamanaidu Modepalli
- Marine Biological Association of the UK, The Laboratory 1 , Citadel Hill, Plymouth PL1 2PB , United Kingdom
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Effect of Air Exposure-Induced Hypoxia on Neurotransmitters and Neurotransmission Enzymes in Ganglia of the Scallop Azumapecten farreri. Int J Mol Sci 2022; 23:ijms23042027. [PMID: 35216143 PMCID: PMC8878441 DOI: 10.3390/ijms23042027] [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] [Received: 12/08/2021] [Revised: 02/09/2022] [Accepted: 02/09/2022] [Indexed: 02/04/2023] Open
Abstract
The nervous system expresses neuromolecules that play a crucial role in regulating physiological processes. Neuromolecule synthesis can be regulated by oxygen-dependent enzymes. Bivalves are a convenient model for studying air exposure-induced hypoxia. Here, we studied the effects of hypoxia on the expression and dynamics of neurotransmitters, and on neurotransmitter enzyme distribution, in the central nervous system (CNS) of the scallop Azumapecten farreri. We analyzed the expression of the neurotransmitters FMRFamide and serotonin (5-HT) and the choline acetyltransferase (CHAT) and universal NO-synthase (uNOS) enzymes during air exposure-induced hypoxia. We found that, in early-stage hypoxia, total serotonin content decreased in some CNS regions but increased in others. CHAT-lir cell numbers increased in all ganglia after hypoxia; CHAT probably appears de novo in accessory ganglia. Short-term hypoxia caused increased uNOS-lir cell numbers, while long-term exposure led to a reduction in their number. Thus, hypoxia weakly influences the number of FMRFamide-lir neurons in the visceral ganglion and does not affect peptide expression in the pedal ganglion. Ultimately, we found that the localization and level of synthesis of neuromolecules, and the numbers of cells expressing these molecules, vary in the scallop CNS during hypoxia exposure. This indicates their possible involvement in hypoxia resistance mechanisms.
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Marinković M, Berger J, Jékely G. Neuronal coordination of motile cilia in locomotion and feeding. Philos Trans R Soc Lond B Biol Sci 2019; 375:20190165. [PMID: 31884921 PMCID: PMC7017327 DOI: 10.1098/rstb.2019.0165] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Efficient ciliary locomotion and transport require the coordination of motile cilia. Short-range coordination of ciliary beats can occur by biophysical mechanisms. Long-range coordination across large or disjointed ciliated fields often requires nervous system control and innervation of ciliated cells by ciliomotor neurons. The neuronal control of cilia is best understood in invertebrate ciliated microswimmers, but similar mechanisms may operate in the vertebrate body. Here, we review how the study of aquatic invertebrates contributed to our understanding of the neuronal control of cilia. We summarize the anatomy of ciliomotor systems and the physiological mechanisms that can alter ciliary activity. We also discuss the most well-characterized ciliomotor system, that of the larval annelid Platynereis. Here, pacemaker neurons drive the rhythmic activation of cholinergic and serotonergic ciliomotor neurons to induce ciliary arrests and beating. The Platynereis ciliomotor neurons form a distinct part of the larval nervous system. Similar ciliomotor systems likely operate in other ciliated larvae, such as mollusc veligers. We discuss the possible ancestry and conservation of ciliomotor circuits and highlight how comparative experimental approaches could contribute to a better understanding of the evolution and function of ciliary systems. This article is part of the Theo Murphy meeting issue ‘Unity and diversity of cilia in locomotion and transport’.
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Affiliation(s)
- Milena Marinković
- Living Systems Institute, University of Exeter, Stocker Road, Exeter EX4 4QD, UK
| | - Jürgen Berger
- Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
| | - Gáspár Jékely
- Living Systems Institute, University of Exeter, Stocker Road, Exeter EX4 4QD, UK
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Johnston CU, Clothier LN, Quesnel DM, Gieg LM, Chua G, Hermann PM, Wildering WC. Embryonic exposure to model naphthenic acids delays growth and hatching in the pond snail Lymnaea stagnalis. CHEMOSPHERE 2017; 168:1578-1588. [PMID: 27932040 DOI: 10.1016/j.chemosphere.2016.11.156] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 11/28/2016] [Accepted: 11/29/2016] [Indexed: 06/06/2023]
Abstract
Naphthenic acids (NAs), a class of structurally diverse carboxylic acids with often complex ring structures and large aliphatic tail groups, are important by-products of many petrochemical processes including the oil sands mining activity of Northern Alberta. While it is evident that NAs have both acute and chronic harmful effects on many organisms, many aspects of their toxicity remain to be clarified. Particularly, while substantive data sets have been collected on NA toxicity in aquatic prokaryote and vertebrate model systems, to date, nothing is known about the toxic effects of these compounds on the embryonic development of aquatic invertebrate taxa, including freshwater mollusks. This study examines under laboratory conditions the toxicity of NAs extracted from oil sands process water (OSPW) and the low-molecular weight model NAs cyclohexylsuccinic acid (CHSA), cyclohexanebutyric acid (CHBA), and 4-tert-butylcyclohexane carboxylic acid (4-TBCA) on embryonic development of the snail Lymnaea stagnalis, a common freshwater gastropod with a broad Palearctic distribution. Evidence is provided for concentration-dependent teratogenic effects of both OSPW-derived and model NAs with remarkably similar nominal threshold concentrations between 15 and 20 mg/L and 28d EC50 of 31 mg/L. In addition, the data provide evidence for substantial toxicokinetic differences between CHSA, CHBA and 4-TBCA. Together, our study introduces Lymnaea stagnalis embryonic development as an effective model to assay NA-toxicity and identifies molecular architecture as a potentially important toxicokinetic parameter in the toxicity of low-molecular weight NA in embryonic development of aquatic gastropods.
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Affiliation(s)
- Christina U Johnston
- Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, AB, T2N 1N4, Canada
| | - Lindsay N Clothier
- Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, AB, T2N 1N4, Canada
| | - Dean M Quesnel
- Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, AB, T2N 1N4, Canada
| | - Lisa M Gieg
- Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, AB, T2N 1N4, Canada
| | - Gordon Chua
- Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, AB, T2N 1N4, Canada
| | - Petra M Hermann
- Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, AB, T2N 1N4, Canada; Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - Willem C Wildering
- Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, AB, T2N 1N4, Canada; Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB, T2N 4N1, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada.
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Zotin AA, Kirik EF. Individual growth of the great ramshorn snail Planorbarius corneus (Gastropoda, Planorbidae) embryos. Russ J Dev Biol 2016. [DOI: 10.1134/s1062360416050106] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Ivashkin E, Khabarova MY, Melnikova V, Nezlin LP, Kharchenko O, Voronezhskaya EE, Adameyko I. Serotonin Mediates Maternal Effects and Directs Developmental and Behavioral Changes in the Progeny of Snails. Cell Rep 2015; 12:1144-58. [PMID: 26257175 DOI: 10.1016/j.celrep.2015.07.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Revised: 05/27/2015] [Accepted: 07/13/2015] [Indexed: 10/23/2022] Open
Abstract
Many organisms survive in constantly changing environments, including cycling seasons. Developing embryos show remarkable instant adaptations to the variable environmental challenges they encounter during their adult life, despite having no direct contact with the changing environment until after birth or hatching. The mechanisms by which such non-genetic information is transferred to the developing embryos are largely unknown. Here, we address this question by using a freshwater pond snail (Lymnaea stagnalis) as a model system. This snail normally lives in a seasonal climate, and the seasons define its locomotion, feeding, and reproductive behavior. We discovered that the serotonergic system plays a crucial role in transmitting a non-genetic instructive signal from mother to progeny. This maternal serotonin-based signal functions in embryos during a short time window at exclusively early pre-neural developmental stages and modulates the dynamics of embryonic and juvenile growth, feeding behavior, and locomotion.
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Affiliation(s)
- Evgeny Ivashkin
- Department of Experimental Neurocytology, Brain Research Branch, Scientific Center of Neurology, Russian Academy of Medical Sciences, 105064 Moscow, Russia; Department of Physiology and Pharmacology, Karolinska Institutet, 17177 Solna, Sweden
| | - Marina Yu Khabarova
- Institute of Developmental Biology, Russian Academy of Sciences, 119334 Moscow, Russia
| | - Victoria Melnikova
- Institute of Developmental Biology, Russian Academy of Sciences, 119334 Moscow, Russia
| | - Leonid P Nezlin
- Institute of Developmental Biology, Russian Academy of Sciences, 119334 Moscow, Russia
| | - Olga Kharchenko
- Institute of Developmental Biology, Russian Academy of Sciences, 119334 Moscow, Russia
| | - Elena E Voronezhskaya
- Institute of Developmental Biology, Russian Academy of Sciences, 119334 Moscow, Russia.
| | - Igor Adameyko
- Department of Physiology and Pharmacology, Karolinska Institutet, 17177 Solna, Sweden; Department of Molecular Neurosciences, Center of Brain Research, Medical University of Vienna, 1090 Vienna, Austria.
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Glebov K, Voronezhskaya EE, Khabarova MY, Ivashkin E, Nezlin LP, Ponimaskin EG. Mechanisms underlying dual effects of serotonin during development of Helisoma trivolvis (Mollusca). BMC DEVELOPMENTAL BIOLOGY 2014; 14:14. [PMID: 24625099 PMCID: PMC4007640 DOI: 10.1186/1471-213x-14-14] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2013] [Accepted: 02/21/2014] [Indexed: 11/10/2022]
Abstract
BACKGROUND Serotonin (5-HT) is well known as widely distributed modulator of developmental processes in both vertebrates and invertebrates. It is also the earliest neurotransmitter to appear during neuronal development. In aquatic invertebrates, which have larvae in their life cycle, 5-HT is involved in regulation of stages transition including larval metamorphosis and settlement. However, molecular and cellular mechanisms underlying developmental transition in aquatic invertebrate species are yet poorly understood. Earlier we demonstrated that in larvae of freshwater molluscs and marine polychaetes, endogenous 5-HT released from the neurons of the apical sensory organ (ASO) in response to external stimuli retarded larval development at premetamorphic stages, and accelerated it at metamorphic stages. Here we used a freshwater snail Helisoma trivolvis to study molecular mechanisms underlying these dual developmental effects of 5-HT. RESULTS Larval development of H. trivolvis includes transition from premetamorphic to metamorphic stages and shares the main features of metamorphosis with free-swimming aquatic larvae. Three types of 5-HT receptors (5-HT1-, 5-HT4- and 5-HT7-like) are functionally active at premetamorphic (trochophore, veliger) and metamorphic (veliconcha) stages, and expression patterns of these receptors and respective G proteins undergo coordinated changes during development. Stimulation of these receptors modulated cAMP-dependent regulation of cell divisions. Expression of 5-HT4- and 5-HT7-like receptors and their downstream Gs protein was down-regulated during the transition of pre- to metamorphic stage, while expression of 5-HT1 -like receptor and its downstream Gi protein was upregulated. In accordance with relative amount of these receptors, stimulation of 5-HTRs at premetamorphic stages induces developmental retardation, while their stimulation at metamorphic stages induces developmental acceleration. CONCLUSIONS We present a novel molecular mechanism that underlies stage-specific changes in developmental tempo of H. trivolvis larvae in response to endogenous 5-HT produced by the neurons of the ASO. We suggest that consecutive changes in expression patterns of different receptors and their downstream partners in the course of larval development represent the molecular base of larval transition from premetamorphic (non-competent) to metamorphic (competent) state.
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Affiliation(s)
| | | | | | | | | | - Evgeni G Ponimaskin
- DFG-Research Center Molecular Physiology of the Brain (CMPB), Göttingen, Germany.
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Walentek P, Bogusch S, Thumberger T, Vick P, Dubaissi E, Beyer T, Blum M, Schweickert A. A novel serotonin-secreting cell type regulates ciliary motility in the mucociliary epidermis of Xenopus tadpoles. Development 2014; 141:1526-33. [PMID: 24598162 DOI: 10.1242/dev.102343] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The embryonic skin of Xenopus tadpoles serves as an experimental model system for mucociliary epithelia (MCE) such as the human airway epithelium. MCEs are characterized by the presence of mucus-secreting goblet and multiciliated cells (MCCs). A third cell type, ion-secreting cells (ISCs), is present in the larval skin as well. Synchronized beating of MCC cilia is required for directional transport of mucus. Here we describe a novel cell type in the Xenopus laevis larval epidermis, characterized by serotonin synthesis and secretion. It is termed small secretory cell (SSC). SSCs are detectable at early tadpole stages, unlike MCCs and ISCs, which are specified at early neurulation. Subcellularly, serotonin was found in large, apically localized vesicle-like structures, which were entirely shed into the surrounding medium. Pharmacological inhibition of serotonin synthesis decreased the velocity of cilia-driven fluid flow across the skin epithelium. This effect was mediated by serotonin type 3 receptor (Htr3), which was expressed in ciliated cells. Knockdown of Htr3 compromised flow velocity by reducing the ciliary motility of MCCs. SSCs thus represent a distinct and novel entity of the frog tadpole MCE, required for ciliary beating and mucus transport across the larval skin. The identification and characterization of SSCs consolidates the value of the Xenopus embryonic skin as a model system for human MCEs, which have been known for serotonin-dependent regulation of ciliary beat frequency.
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Affiliation(s)
- Peter Walentek
- University of Hohenheim, Institute of Zoology, Garbenstrasse 30, D-70593 Stuttgart, Germany
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