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Loss CM, Melleu FF, Domingues K, Lino-de-Oliveira C, Viola GG. Combining Animal Welfare With Experimental Rigor to Improve Reproducibility in Behavioral Neuroscience. Front Behav Neurosci 2021; 15:763428. [PMID: 34916915 PMCID: PMC8671008 DOI: 10.3389/fnbeh.2021.763428] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Accepted: 10/18/2021] [Indexed: 02/05/2023] Open
Affiliation(s)
- Cássio Morais Loss
- Molecular and Behavioral Neuroscience Laboratory, Departamento de Farmacologia, Universidade Federal de São Paulo, São Paulo, Brazil
- National Institute for Translational Medicine (INCT-TM), National Council for Scientific and Technological Development (CNPq/CAPES/FAPESP), Ribeirão Preto, Brazil
| | | | - Karolina Domingues
- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
| | - Cilene Lino-de-Oliveira
- Departamento de Ciências Fisiológicas do Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Brazil
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Jacobs B, Rally H, Doyle C, O'Brien L, Tennison M, Marino L. Putative neural consequences of captivity for elephants and cetaceans. Rev Neurosci 2021; 33:439-465. [PMID: 34534428 DOI: 10.1515/revneuro-2021-0100] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Accepted: 09/02/2021] [Indexed: 12/20/2022]
Abstract
The present review assesses the potential neural impact of impoverished, captive environments on large-brained mammals, with a focus on elephants and cetaceans. These species share several characteristics, including being large, wide-ranging, long-lived, cognitively sophisticated, highly social, and large-brained mammals. Although the impact of the captive environment on physical and behavioral health has been well-documented, relatively little attention has been paid to the brain itself. Here, we explore the potential neural consequences of living in captive environments, with a focus on three levels: (1) The effects of environmental impoverishment/enrichment on the brain, emphasizing the negative neural consequences of the captive/impoverished environment; (2) the neural consequences of stress on the brain, with an emphasis on corticolimbic structures; and (3) the neural underpinnings of stereotypies, often observed in captive animals, underscoring dysregulation of the basal ganglia and associated circuitry. To this end, we provide a substantive hypothesis about the negative impact of captivity on the brains of large mammals (e.g., cetaceans and elephants) and how these neural consequences are related to documented evidence for compromised physical and psychological well-being.
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Affiliation(s)
- Bob Jacobs
- Laboratory of Quantitative Neuromorphology, Neuroscience Program, Colorado College, Colorado Springs, CO, 80903, USA
| | - Heather Rally
- Foundation to Support Animal Protection, Norfolk, VA, 23510, USA
| | - Catherine Doyle
- Performing Animal Welfare Society, P.O. Box 849, Galt, CA, 95632, USA
| | - Lester O'Brien
- Palladium Elephant Consulting Inc., 2408 Pinewood Dr. SE, Calgary, AB, T2B1S4, Canada
| | - Mackenzie Tennison
- Department of Psychology, University of Washington, Seattle, WA, 98195, USA
| | - Lori Marino
- Whale Sanctuary Project, Kanab, UT, 84741, USA
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Exum AC, Sun LM, Herberholz J. Discrete modulation of anti-predatory and agonistic behaviors by sensory communication signals in juvenile crayfish. ACTA ACUST UNITED AC 2020; 223:jeb.226704. [PMID: 32457062 DOI: 10.1242/jeb.226704] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 05/19/2020] [Indexed: 01/14/2023]
Abstract
We investigated how the exchange of sensory signals modulates the individual behaviors of juvenile crayfish in an anti-predatory context as well as during intraspecific agonistic encounters. We first compared crayfish housed in total sensory isolation or in pairs with access to chemical and visual cues. After 1 week of housing, we analysed their individual responses to a visual danger signal while they were foraging. We found that crayfish previously housed in pairs with exchange of sensory signals responded to a simulated predator attack predominantly with freezing behavior, whereas animals deprived of all sensory communication mostly responded by performing escape tail-flips. Next, we used the same housing conditions in between repeated fights in pairs of crayfish. Aggressive and submissive behaviors increased in subsequent fights both after total isolation and after exchange of olfactory and visual signals. Thus, unlike responses to simulated predator attacks, intraspecific agonistic behavior was not modulated by exposure to the same sensory signals. However, when we tested the effects of olfactory or visual communication independently, aggression increased dramatically after the exchange of olfactory signals, which also led to a high number of rank reversals in second fights, suggesting a destabilization of the original dominance relationship. Exposure to visual cues during the 1-week separation, however, produced the opposite effect, reducing agonistic behaviors and rank reversals. These findings demonstrate that exchange of sensory signals modulates future anti-predatory decision-making and intraspecific agonistic behaviors discretely, suggesting that the effect of these signals on shared neural circuitry is context dependent.
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Affiliation(s)
- Alexis C Exum
- Department of Psychology, University of Maryland, College Park, MD 20742, USA
| | - Lucky M Sun
- Department of Psychology, University of Maryland, College Park, MD 20742, USA
| | - Jens Herberholz
- Department of Psychology, University of Maryland, College Park, MD 20742, USA .,Neuroscience and Cognitive Science Program, University of Maryland, College Park, MD 20742, USA
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Brenneis G, Beltz BS. Adult neurogenesis in crayfish: Origin, expansion, and migration of neural progenitor lineages in a pseudostratified neuroepithelium. J Comp Neurol 2019; 528:1459-1485. [PMID: 31743442 DOI: 10.1002/cne.24820] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 09/05/2019] [Accepted: 11/14/2019] [Indexed: 02/04/2023]
Abstract
Two decades after the discovery of adult-born neurons in the brains of decapod crustaceans, the deutocerebral proliferative system (DPS) producing these neural lineages has become a model of adult neurogenesis in invertebrates. Studies on crayfish have provided substantial insights into the anatomy, cellular dynamics, and regulation of the DPS. Contrary to traditional thinking, recent evidence suggests that the neurogenic niche in the crayfish DPS lacks self-renewing stem cells, its cell pool being instead sustained via integration of hemocytes generated by the innate immune system. Here, we investigated the origin, division and migration patterns of the adult-born neural progenitor (NP) lineages in detail. We show that the niche cell pool is not only replenished by hemocyte integration but also by limited numbers of symmetric cell divisions with some characteristics reminiscent of interkinetic nuclear migration. Once specified in the niche, first generation NPs act as transit-amplifying intermediate NPs that eventually exit and produce multicellular clones as they move along migratory streams toward target brain areas. Different clones may migrate simultaneously in the streams but occupy separate tracks and show spatio-temporally flexible division patterns. Based on this, we propose an extended DPS model that emphasizes structural similarities to pseudostratified neuroepithelia in other arthropods and vertebrates. This model includes hemocyte integration and intrinsic cell proliferation to synergistically counteract niche cell pool depletion during the animal's lifespan. Further, we discuss parallels to recent findings on mammalian adult neurogenesis, as both systems seem to exhibit a similar decoupling of proliferative replenishment divisions and consuming neurogenic divisions.
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Affiliation(s)
- Georg Brenneis
- Wellesley College, Neuroscience Program, Wellesley, Massachusetts, USA.,Universität Greifswald, Zoologisches Institut und Museum, AG Cytologie und Evolutionsbiologie, Greifswald, Germany
| | - Barbara S Beltz
- Wellesley College, Neuroscience Program, Wellesley, Massachusetts, USA
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5
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Wittfoth C, Harzsch S. Adult neurogenesis in the central olfactory pathway of dendrobranchiate and caridean shrimps: New insights into the evolution of the deutocerebral proliferative system in reptant decapods. Dev Neurobiol 2018; 78:757-774. [PMID: 29663684 DOI: 10.1002/dneu.22596] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 04/09/2018] [Accepted: 04/09/2018] [Indexed: 11/10/2022]
Abstract
Persistent neurogenesis in the central olfactory pathway characterizes many reptant decapods such as lobsters, crayfish and crabs. In these animals, the deutocerebral proliferative system generates new neurons which integrate into the neuronal network of the first order processing neuropil of the olfactory system, the deutocerebral chemosensory lobes (also called olfactory lobes). However, differences concerning the phenotype and the mechanisms that drive adult neurogenesis were reported in crayfish versus spiny lobsters. While numerous studies have focussed on these mechanisms and regulation of adult neurogenesis, investigations about the phylogenetic distribution are missing. To contribute an evolutionary perspective on adult neurogenesis in decapods, we investigated two representatives of basally diverging lineages, the dendrobranchiate Penaeus vannamei and the caridean Crangon crangon using the thymidine analogue Bromodeoxyuridine (BrdU) as marker for the S phase of cycling cells. Compared to reptant decapods, our results suggest a simpler mechanism of neurogenesis in the adult brain of dendrobranchiate and caridean shrimps. Observed differences in the rate of proliferation and spatial dimensions are suggested to correlate with the complexity of the olfactory system. We assume that a more complex and mitotically more active proliferative system in reptant decapods evolved with the emergence of another processing neuropil, the accessory lobes. © 2018 Wiley Periodicals, Inc. Develop Neurobiol, 2018.
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Affiliation(s)
- Christin Wittfoth
- Department of Cytology and Evolutionary Biology, Ernst-Moritz-Arndt University of Greifswald, Zoological Institute & Museum, Greifswald, Germany
- Alfred Wegener Institute for Polar and Marine Research, Biologische Anstalt Helgoland, Helgoland, Germany
| | - Steffen Harzsch
- Department of Cytology and Evolutionary Biology, Ernst-Moritz-Arndt University of Greifswald, Zoological Institute & Museum, Greifswald, Germany
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Beltz BS, Benton JL. From Blood to Brain: Adult-Born Neurons in the Crayfish Brain Are the Progeny of Cells Generated by the Immune System. Front Neurosci 2017; 11:662. [PMID: 29270102 PMCID: PMC5725445 DOI: 10.3389/fnins.2017.00662] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 11/13/2017] [Indexed: 11/23/2022] Open
Abstract
New neurons continue to be born and integrated into the brains of adult decapod crustaceans. Evidence in crayfish indicates that the 1st-generation neural precursors that generate these adult-born neurons originate in the immune system and travel to the neurogenic niche via the circulatory system. These precursors are attracted to the niche, become integrated amongst niche cells, and undergo mitosis within a few days; both daughters of this division migrate away from the niche toward the brain clusters where they will divide again and differentiate into neurons. In the crustacean brain, the rate of neuronal production is highly sensitive to serotonin (5-hydroxytryptamine, 5-HT) levels. These effects are lineage-dependent, as serotonin's influence is limited to late 2nd-generation neural precursors and their progeny. Experiments indicate that serotonin regulates adult neurogenesis in the crustacean brain by multiple mechanisms: via direct effects of serotonin released from brain neurons into the hemolymph or by local release onto target cells, or by indirect influences via a serotonin-mediated release of agents from other regions, such as hormones from the sinus gland and cytokines from hematopoietic tissues. Evidence in crayfish also indicates that serotonin mediates the attraction of neural precursors generated by the immune system to the neurogenic niche. Thus, studies in the crustacean brain have revealed multiple roles for this monoamine in adult neurogenesis, and identified several pathways by which serotonin influences the generation of new neurons.
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Affiliation(s)
- Barbara S Beltz
- Neuroscience Program, Wellesley College, Wellesley, MA, United States
| | - Jeanne L Benton
- Neuroscience Program, Wellesley College, Wellesley, MA, United States
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Bertapelle C, Polese G, Di Cosmo A. Enriched Environment Increases PCNA and PARP1 Levels in Octopus vulgaris Central Nervous System: First Evidence of Adult Neurogenesis in Lophotrochozoa. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2017; 328:347-359. [PMID: 28251828 DOI: 10.1002/jez.b.22735] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Revised: 01/25/2017] [Accepted: 01/30/2017] [Indexed: 11/09/2022]
Abstract
Organisms showing a complex and centralized nervous system, such as teleosts, amphibians, reptiles, birds and mammals, and among invertebrates, crustaceans and insects, can adjust their behavior according to the environmental challenges. Proliferation, differentiation, migration, and axonal and dendritic development of newborn neurons take place in brain areas where structural plasticity, involved in learning, memory, and sensory stimuli integration, occurs. Octopus vulgaris has a complex and centralized nervous system, located between the eyes, with a hierarchical organization. It is considered the most "intelligent" invertebrate for its advanced cognitive capabilities, as learning and memory, and its sophisticated behaviors. The experimental data obtained by immunohistochemistry and western blot assay using proliferating cell nuclear antigen and poli (ADP-ribose) polymerase 1 as marker of cell proliferation and synaptogenesis, respectively, reviled cell proliferation in areas of brain involved in learning, memory, and sensory stimuli integration. Furthermore, we showed how enriched environmental conditions affect adult neurogenesis.
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Affiliation(s)
- Carla Bertapelle
- Department of Biology, University of Napoli Federico II, Naples, NA, Italy
| | - Gianluca Polese
- Department of Biology, University of Napoli Federico II, Naples, NA, Italy
| | - Anna Di Cosmo
- Department of Biology, University of Napoli Federico II, Naples, NA, Italy
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Powers AS. Plasticity and Adult Neurogenesis in Amphibians and Reptiles: More Questions than Answers. BRAIN, BEHAVIOR AND EVOLUTION 2016; 87:175-183. [DOI: 10.1159/000447047] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Studies of the relationship between behavioral plasticity and new cells in the adult brain in amphibians and reptiles are sparse but demonstrate that environmental and hormonal variables do have an effect on the amount of cell proliferation and/or migration. The variables that are reviewed here are: enriched environment, social stimulation, spatial area use, season, photoperiod and temperature, and testosterone. Fewer data are available for amphibians than for reptiles, but for both groups many issues are still to be resolved. It is to be hoped that the questions raised here will generate more answers in future studies.
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Harzsch S, von Bohlen und Halbach O. A possible role for the immune system in adult neurogenesis: new insights from an invertebrate model. ZOOLOGY 2016; 119:153-157. [DOI: 10.1016/j.zool.2015.11.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 11/30/2015] [Indexed: 10/22/2022]
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Beltz BS, Cockey EL, Li J, Platto JF, Ramos KA, Benton JL. Adult neural stem cells: Long-term self-renewal, replenishment by the immune system, or both? Bioessays 2015; 37:495-501. [PMID: 25761245 DOI: 10.1002/bies.201400198] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The current model of adult neurogenesis in mammals suggests that adult-born neurons are generated by stem cells that undergo long-term self-renewal, and that a lifetime supply of stem cells resides in the brain. In contrast, it has recently been demonstrated that adult-born neurons in crayfish are generated by precursors originating in the immune system. This is particularly interesting because studies done many years ago suggest that a similar mechanism might exist in rodents and humans, with bone marrow providing stem cells that can generate neurons. However, the relevance of these findings for natural mechanisms underlying adult neurogenesis in mammals is not clear, because of uncertainties at many levels. We argue here that the recent findings in crayfish send a strong signal to re-examine existing data from rodents and humans, and to design new experiments that will directly test the contributions of the immune system to adult neurogenesis in mammals.
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Kim YF, Sandeman DC, Benton JL, Beltz BS. Birth, survival and differentiation of neurons in an adult crustacean brain. Dev Neurobiol 2013; 74:602-15. [PMID: 24339155 DOI: 10.1002/dneu.22156] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Revised: 11/22/2013] [Accepted: 11/24/2013] [Indexed: 02/06/2023]
Abstract
Life-long neurogenesis is a characteristic feature of many vertebrate and invertebrate species. In decapod crustaceans, new neurons are added throughout life to two cell clusters containing local (cluster 9) and projection (cluster 10) interneurons in the olfactory pathway. Adult-born neurons in clusters 9 and 10 in crayfish have the anatomical properties and chemistry of mature neurons by 6 months after birth. Here we use 5-bromo-2'-deoxyuridine (BrdU) incorporation to pulse label mitotically active cells in these cell clusters, followed by a survival time of up to 8 months, during which crayfish (Cherax destructor) were sacrificed at intervals and the numbers of BrdU-labeled cells quantified. We find a decrease in the numbers of BrdU-labeled cells in cell cluster 10 between the first and second weeks following BrdU exposure, suggesting a period of cell death shortly after proliferation. Additional delayed cell divisions in both cell clusters are indicated by increases in labeled cells long after the BrdU clearing time. The differentiation time of these cells into neurons was defined by detection of the first immunoreactivity for the transmitter SIFamide in cluster 10 BrdU-labeled cells, which begins at 4 weeks after BrdU labeling; the numbers of SIFamide-labeled cells continues to increase over the following month. Experiments testing whether proliferation and survival of Cluster 10 cells are influenced by locomotor activity provided no evidence of a correlation between activity levels and cell proliferation, but suggest a strong influence of locomotor activity on cell survival.
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Affiliation(s)
- Youngmi Faith Kim
- Neuroscience Program, Wellesley College, Wellesley, Massachusetts, 02481
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12
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Adult neurogenesis: ultrastructure of a neurogenic niche and neurovascular relationships. PLoS One 2012; 7:e39267. [PMID: 22723980 PMCID: PMC3378523 DOI: 10.1371/journal.pone.0039267] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 05/22/2012] [Indexed: 01/06/2023] Open
Abstract
The first-generation precursors producing adult-born neurons in the crayfish (Procambarus clarkii) brain reside in a specialized niche located on the ventral surface of the brain. In the present work, we have explored the organization and ultrastructure of this neurogenic niche, using light-level, confocal and electron microscopic approaches. Our goals were to define characteristics of the niche microenvironment, examine the morphological relationships between the niche and the vasculature and observe specializations at the boundary between the vascular cavity located centrally in the niche. Our results show that the niche is almost fully encapsulated by blood vessels, and that cells in the vasculature come into contact with the niche. This analysis also characterizes the ultrastructure of the cell types in the niche. The Type I niche cells are by far the most numerous, and are the only cell type present superficially in the most ventral cell layers of the niche. More dorsally, Type I cells are intermingled with Types II, III and IV cells, which are observed far less frequently. Type I cells have microvilli on their apical cell surfaces facing the vascular cavity, as well as junctional complexes between adjacent cells, suggesting a role in regulating transport from the blood into the niche cells. These studies demonstrate a close relationship between the neurogenic niche and vascular system in P. clarkii. Furthermore, the specializations of niche cells contacting the vascular cavity are also typical of the interface between the blood/cerebrospinal fluid (CSF)-brain barriers of vertebrates, including cells of the subventricular zone (SVZ) producing new olfactory interneurons in mammals. These data indicate that tissues involved in producing adult-born neurons in the crayfish brain use strategies that may reflect fundamental mechanisms preserved in an evolutionarily broad range of species, as proposed previously. The studies described here extend our understanding of neurovascular relationships in the brain of P. clarkii by characterizing the organization and ultrastructure of the neurogenic niche and associated vascular tissues.
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Beltz BS, Zhang Y, Benton JL, Sandeman DC. Adult neurogenesis in the decapod crustacean brain: a hematopoietic connection? Eur J Neurosci 2012; 34:870-83. [PMID: 21929622 DOI: 10.1111/j.1460-9568.2011.07802.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
New neurons are produced and integrated into circuits in the adult brains of many organisms, including crustaceans. In some crustacean species, the first-generation neuronal precursors reside in a niche exhibiting characteristics analogous to mammalian neurogenic niches. However, unlike mammalian niches where several generations of neuronal precursors co-exist, the lineage of precursor cells in crayfish is spatially separated allowing the influence of environmental and endogenous regulators on specific generations in the neuronal precursor lineage to be defined. Experiments also demonstrate that the first-generation neuronal precursors in the crayfish Procambarus clarkii are not self-renewing. A source external to the neurogenic niche must therefore provide cells that replenish the first-generation precursor pool, because although these cells divide and produce a continuous efflux of second-generation cells from the niche, the population of first-generation niche precursors is not diminished with growth and aging. In vitro studies show that cells extracted from the hemolymph, but not other tissues, are attracted to and incorporated into the neurogenic niche, a phenomenon that appears to involve serotonergic mechanisms. We propose that, in crayfish, the hematopoietic system may be a source of cells that replenish the niche cell pool. These and other studies reviewed here establish decapod crustaceans as model systems in which the processes underlying adult neurogenesis, such as stem cell origins and transformation, can be readily explored. Studies in diverse species where adult neurogenesis occurs will result in a broader understanding of fundamental mechanisms and how evolutionary processes may have shaped the vertebrate/mammalian condition.
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Affiliation(s)
- Barbara S Beltz
- Neuroscience Program, Wellesley College, 106 Central Street, Wellesley, MA 02481, USA.
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Sintoni S, Benton JL, Beltz BS, Hansson BS, Harzsch S. Neurogenesis in the central olfactory pathway of adult decapod crustaceans: development of the neurogenic niche in the brains of procambarid crayfish. Neural Dev 2012; 7:1. [PMID: 22225949 PMCID: PMC3266201 DOI: 10.1186/1749-8104-7-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Accepted: 01/06/2012] [Indexed: 12/13/2022] Open
Abstract
Background In the decapod crustacean brain, neurogenesis persists throughout the animal's life. After embryogenesis, the central olfactory pathway integrates newborn olfactory local and projection interneurons that replace old neurons or expand the existing population. In crayfish, these neurons are the descendants of precursor cells residing in a neurogenic niche. In this paper, the development of the niche was documented by monitoring proliferating cells with S-phase-specific markers combined with immunohistochemical, dye-injection and pulse-chase experiments. Results Between the end of embryogenesis and throughout the first post-embryonic stage (POI), a defined transverse band of mitotically active cells (which we will term 'the deutocerebral proliferative system' (DPS) appears. Just prior to hatching and in parallel with the formation of the DPS, the anlagen of the niche appears, closely associated with the vasculature. When the hatchling molts to the second post-embryonic stage (POII), the DPS differentiates into the lateral (LPZ) and medial (MPZ) proliferative zones. The LPZ and MPZ are characterized by a high number of mitotically active cells from the beginning of post-embryonic life; in contrast, the developing niche contains only very few dividing cells, a characteristic that persists in the adult organism. Conclusions Our data suggest that the LPZ and MPZ are largely responsible for the production of new neurons in the early post-embryonic stages, and that the neurogenic niche in the beginning plays a subordinate role. However, as the neuroblasts in the proliferation zones disappear during early post-embryonic life, the neuronal precursors in the niche gradually become the dominant and only mechanism for the generation of new neurons in the adult brain.
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Affiliation(s)
- Silvia Sintoni
- Max Planck Institute for Chemical Ecology, Department of Evolutionary Neuroethology, Hans-Knöll-Straße 8, D-07745 Jena, Germany
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Benton JL, Zhang Y, Kirkhart CR, Sandeman DC, Beltz BS. Primary neuronal precursors in adult crayfish brain: replenishment from a non-neuronal source. BMC Neurosci 2011; 12:53. [PMID: 21635768 PMCID: PMC3127996 DOI: 10.1186/1471-2202-12-53] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Accepted: 06/02/2011] [Indexed: 12/12/2022] Open
Abstract
Background Adult neurogenesis, the production and integration of new neurons into circuits in the brains of adult animals, is a common feature of a variety of organisms, ranging from insects and crustaceans to birds and mammals. In the mammalian brain the 1st-generation neuronal precursors, the astrocytic stem cells, reside in neurogenic niches and are reported to undergo self-renewing divisions, thereby providing a source of new neurons throughout an animal's life. In contrast, our work shows that the 1st-generation neuronal precursors in the crayfish (Procambarus clarkii) brain, which also have glial properties and lie in a neurogenic niche resembling that of vertebrates, undergo geometrically symmetrical divisions and both daughters appear to migrate away from the niche. However, in spite of this continuous efflux of cells, the number of neuronal precursors in the crayfish niche continues to expand as the animals grow and age. Based on these observations we have hypothesized that (1) the neuronal stem cells in the crayfish brain are not self-renewing, and (2) a source external to the neurogenic niche must provide cells that replenish the stem cell pool. Results In the present study, we tested the first hypothesis using sequential double nucleoside labeling to track the fate of 1st- and 2nd-generation neuronal precursors, as well as testing the size of the labeled stem cell pool following increasing incubation times in 5-bromo-2'-deoxyuridine (BrdU). Our results indicate that the 1st-generation precursor cells in the crayfish brain, which are functionally analogous to neural stem cells in vertebrates, are not a self-renewing population. In addition, these studies establish the cycle time of these cells. In vitro studies examining the second hypothesis show that Cell Tracker™ Green-labeled cells extracted from the hemolymph, but not other tissues, are attracted to and incorporated into the neurogenic niche, a phenomenon that appears to involve serotonergic mechanisms. Conclusions These results challenge our current understanding of self-renewal capacity as a defining characteristic of all adult neuronal stem cells. In addition, we suggest that in crayfish, the hematopoietic system may be a source of cells that replenish the niche stem cell pool.
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Affiliation(s)
- Jeanne L Benton
- Neuroscience Program, Wellesley College, 106 Central Street, Wellesley, MA 02481, USA
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