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Webster NB, Meyer NP. Capitella teleta gets left out: possible evolutionary shift causes loss of left tissues rather than increased neural tissue from dominant-negative BMPR1. Neural Dev 2024; 19:4. [PMID: 38698415 PMCID: PMC11067212 DOI: 10.1186/s13064-024-00181-7] [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: 09/18/2023] [Accepted: 03/20/2024] [Indexed: 05/05/2024] Open
Abstract
BACKGROUND The evolution of central nervous systems (CNSs) is a fascinating and complex topic; further work is needed to understand the genetic and developmental homology between organisms with a CNS. Research into a limited number of species suggests that CNSs may be homologous across Bilateria. This hypothesis is based in part on similar functions of BMP signaling in establishing fates along the dorsal-ventral (D-V) axis, including limiting neural specification to one ectodermal region. From an evolutionary-developmental perspective, the best way to understand a system is to explore it in a wide range of organisms to create a full picture. METHODS Here, we expand our understanding of BMP signaling in Spiralia, the third major clade of bilaterians, by examining phenotypes after expression of a dominant-negative BMP Receptor 1 and after knock-down of the putative BMP antagonist Chordin-like using CRISPR/Cas9 gene editing in the annelid Capitella teleta (Pleistoannelida). RESULTS Ectopic expression of the dominant-negative Ct-BMPR1 did not increase CNS tissue or alter overall D-V axis formation in the trunk. Instead, we observed a unique asymmetrical phenotype: a distinct loss of left tissues, including the left eye, brain, foregut, and trunk mesoderm. Adding ectopic BMP4 early during cleavage stages reversed the dominant-negative Ct-BMPR1 phenotype, leading to a similar loss or reduction of right tissues instead. Surprisingly, a similar asymmetrical loss of left tissues was evident from CRISPR knock-down of Ct-Chordin-like but concentrated in the trunk rather than the episphere. CONCLUSIONS Our data highlight a novel asymmetrical phenotype, giving us further insight into the complicated story of BMP's developmental role. We further solidify the hypothesis that the function of BMP signaling during the establishment of the D-V axis and CNS is fundamentally different in at least Pleistoannelida, possibly in Spiralia, and is not required for nervous system delimitation in this group.
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Affiliation(s)
- Nicole B Webster
- Biology Department, Clark University, 950 Main Street, Worcester, MA, 01610, USA
- Biology Department, University of Saskatchewan, 112 Science Place, Saskatoon, SK, S7N 5C8, Canada
| | - Néva P Meyer
- Biology Department, Clark University, 950 Main Street, Worcester, MA, 01610, USA.
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2
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Schuster HC, Hirth F. Phylogenetic tracing of midbrain-specific regulatory sequences suggests single origin of eubilaterian brains. SCIENCE ADVANCES 2023; 9:eade8259. [PMID: 37224241 PMCID: PMC10208574 DOI: 10.1126/sciadv.ade8259] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2022] [Accepted: 04/18/2023] [Indexed: 05/26/2023]
Abstract
Conserved cis-regulatory elements (CREs) control Engrailed-, Pax2-, and dachshund-related gene expression networks directing the formation and function of corresponding midbrain circuits in arthropods and vertebrates. Polarized outgroup analyses of 31 sequenced metazoan genomes representing all animal clades reveal the emergence of Pax2- and dachshund-related CRE-like sequences in anthozoan Cnidaria. The full complement, including Engrailed-related CRE-like sequences, is only detectable in spiralians, ecdysozoans, and chordates that have a brain; they exhibit comparable genomic locations and extensive nucleotide identities that reveal the presence of a conserved core domain, all of which are absent in non-neural genes and, together, distinguish them from randomly assembled sequences. Their presence concurs with a genetic boundary separating the rostral from caudal nervous systems, demonstrated for the metameric brains of annelids, arthropods, and chordates and the asegmental cycloneuralian and urochordate brain. These findings suggest that gene regulatory networks for midbrain circuit formation evolved within the lineage that led to the common ancestor of protostomes and deuterostomes.
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Affiliation(s)
- Helen C. Schuster
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, and Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
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Martín-Zamora FM, Liang Y, Guynes K, Carrillo-Baltodano AM, Davies BE, Donnellan RD, Tan Y, Moggioli G, Seudre O, Tran M, Mortimer K, Luscombe NM, Hejnol A, Marlétaz F, Martín-Durán JM. Annelid functional genomics reveal the origins of bilaterian life cycles. Nature 2023; 615:105-110. [PMID: 36697830 PMCID: PMC9977687 DOI: 10.1038/s41586-022-05636-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 12/07/2022] [Indexed: 01/26/2023]
Abstract
Indirect development with an intermediate larva exists in all major animal lineages1, which makes larvae central to most scenarios of animal evolution2-11. Yet how larvae evolved remains disputed. Here we show that temporal shifts (that is, heterochronies) in trunk formation underpin the diversification of larvae and bilaterian life cycles. We performed chromosome-scale genome sequencing in the annelid Owenia fusiformis with transcriptomic and epigenomic profiling during the life cycles of this and two other annelids. We found that trunk development is deferred to pre-metamorphic stages in the feeding larva of O. fusiformis but starts after gastrulation in the non-feeding larva with gradual metamorphosis of Capitella teleta and the direct developing embryo of Dimorphilus gyrociliatus. Accordingly, the embryos of O. fusiformis develop first into an enlarged anterior domain that forms larval tissues and the adult head12. Notably, this also occurs in the so-called 'head larvae' of other bilaterians13-17, with which the O. fusiformis larva shows extensive transcriptomic similarities. Together, our findings suggest that the temporal decoupling of head and trunk formation, as maximally observed in head larvae, facilitated larval evolution in Bilateria. This diverges from prevailing scenarios that propose either co-option9,10 or innovation11 of gene regulatory programmes to explain larva and adult origins.
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Affiliation(s)
| | - Yan Liang
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK
| | - Kero Guynes
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK
| | | | - Billie E Davies
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK
| | - Rory D Donnellan
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK
| | - Yongkai Tan
- Genomics and Regulatory Systems Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Giacomo Moggioli
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK
| | - Océane Seudre
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK
| | - Martin Tran
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK
- Department of Infectious Disease, Imperial College London, London, UK
| | - Kate Mortimer
- Department of Natural Sciences, Amgueddfa Cymru-Museum Wales, Cardiff, UK
| | - Nicholas M Luscombe
- Genomics and Regulatory Systems Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Andreas Hejnol
- Department of Biological Sciences, University of Bergen, Bergen, Norway
- Institute of Zoology and Evolutionary Research, Faculty of Biological Sciences, Friedrich Schiller University Jena, Jena, Germany
| | - Ferdinand Marlétaz
- Department of Genetics, Evolution and Environment, University College London, London, UK.
| | - José M Martín-Durán
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK.
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4
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Seaver EC. Sifting through the mud: A tale of building the annelid Capitella teleta for EvoDevo studies. Curr Top Dev Biol 2022; 147:401-432. [PMID: 35337457 DOI: 10.1016/bs.ctdb.2021.12.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Over the last few decades, the annelid Capitella teleta has been used increasingly as a study system for investigations of development and regeneration. Its favorable properties include an ability to continuously maintain a laboratory culture, availability of a sequenced genome, a stereotypic cleavage program of early development, substantial regeneration abilities, and established experimental and functional genomics techniques. With this review I tell of my adventure of establishing the Capitella teleta as an emerging model and share examples of a few of the contributions our work has made to the fields of evo-devo and developmental biology. I highlight examples of conservation in developmental programs as well as surprising deviations from existing paradigms that highlight the importance of leveraging biological diversity to shift thinking in the field. The story for each study system is unique, and every animal has its own advantages and disadvantages as an experimental system. Just like most progress in science, it takes strategy, hard work and determination to develop tools and resources for a less studied animal, but luck and serendipity also play a role. I include a few narratives to personalize the science, share details of the story that are not included in typical publications, and provide perspective for investigators who are interested in developing their own study organism.
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Affiliation(s)
- Elaine C Seaver
- Whitney Laboratory for Marine Bioscience, University of Florida, St. Augustine, FL, United States.
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Fofanova E, Mayorova TD, Voronezhskaya EE. Dinophiliformia early neurogenesis suggests the evolution of conservative neural structures across the Annelida phylogenetic tree. PeerJ 2021; 9:e12386. [PMID: 34966573 PMCID: PMC8667735 DOI: 10.7717/peerj.12386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 10/04/2021] [Indexed: 11/27/2022] Open
Abstract
Despite the increasing data concerning the structure of the adult nervous system in various Lophotrochozoa groups, the early events during the neurogenesis of rare and unique groups need clarification. Annelida are a diverse clade of Lophotrochozoa, and their representatives demonstrate a variety of body plans, lifestyles, and life cycles. Comparative data about the early development are available for Errantia, Sedentaria, Sipuncula, and Palaeoannelida; however, our knowledge of Dinophiliformia is currently scarce. Representatives of Dinophiliformia are small interstitial worms combining unique morphological features of different Lophotrochozoan taxa and expressing paedomorphic traits. We describe in detail the early neurogenesis of two related species: Dimorphilus gyrociliatus and Dinophilus vorticoides, from the appearance of first nerve cells until the formation of an adult body plan. In both species, the first cells were detected at the anterior and posterior regions at the early trochophore stage and demonstrated positive reactions with pan-neuronal marker anti-acetylated tubulin only. Long fibers of early cells grow towards each other and form longitudinal bundles along which differentiating neurons later appear and send their processes. We propose that these early cells serve as pioneer neurons, forming a layout of the adult nervous system. The early anterior cell of D. vorticoides is transient and present during the short embryonic period, while early anterior and posterior cells in D. gyrociliatus are maintained throughout the whole lifespan of the species. During development, the growing processes of early cells form compact brain neuropile, paired ventral and lateral longitudinal bundles; unpaired medial longitudinal bundle; and commissures in the ventral hyposphere. Specific 5-HT- and FMRFa-immunopositive neurons differentiate adjacent to the ventral bundles and brain neuropile in the middle trochophore and late trochophore stages, i.e. after the main structures of the nervous system have already been established. Processes of 5-HT- and FMRFa-positive cells constitute a small proportion of the tubulin-immunopositive brain neuropile, ventral cords, and commissures in all developmental stages. No 5-HT- and FMRFa-positive cells similar to apical sensory cells of other Lophotrochozoa were detected. We conclude that: (i) like in Errantia and Sedentaria, Dinophiliformia neurogenesis starts from the peripheral cells, whose processes prefigure the forming adult nervous system, (ii) Dinophiliformia early cells are negative to 5-HT and FMRFa antibodies like Sedentaria pioneer cells.
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Affiliation(s)
- Elizaveta Fofanova
- Department of Comparative and Developmental Physiology, Koltzov Institute of Developmental Biology RAS, Moscow, Russia
| | - Tatiana D Mayorova
- Department of Comparative and Developmental Physiology, Koltzov Institute of Developmental Biology RAS, Moscow, Russia.,Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, Bethesda, Maryland, USA
| | - Elena E Voronezhskaya
- Department of Comparative and Developmental Physiology, Koltzov Institute of Developmental Biology RAS, Moscow, Russia
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Webster NB, Corbet M, Sur A, Meyer NP. Role of BMP signaling during early development of the annelid Capitella teleta. Dev Biol 2021; 478:183-204. [PMID: 34216573 DOI: 10.1016/j.ydbio.2021.06.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Revised: 05/20/2021] [Accepted: 06/22/2021] [Indexed: 11/16/2022]
Abstract
The mechanisms regulating nervous system development are still unknown for a wide variety of taxa. In insects and vertebrates, bone morphogenetic protein (BMP) signaling plays a key role in establishing the dorsal-ventral (D-V) axis and limiting the neuroectoderm to one side of that axis, leading to speculation about the conserved evolution of centralized nervous systems. Studies outside of insects and vertebrates show a more diverse picture of what, if any role, BMP signaling plays in neural development across Bilateria. This is especially true in the morphologically diverse Spiralia (≈Lophotrochozoa). Despite several studies of D-V axis formation and neural induction in spiralians, there is no consensus for how these two processes are related, or whether BMP signaling may have played an ancestral role in either process. To determine the function of BMP signaling during early development of the spiralian annelid Capitella teleta, we incubated embryos and larvae in BMP4 protein for different amounts of time. Adding exogenous BMP protein to early-cleaving C. teleta embryos had a striking effect on formation of the brain, eyes, foregut, and ventral midline in a time-dependent manner. However, adding BMP did not block brain or VNC formation or majorly disrupt the D-V axis. We identified three key time windows of BMP activity. 1) BMP treatment around birth of the 3rd-quartet micromeres caused the loss of the eyes, radialization of the brain, and a reduction of the foregut, which we interpret as a loss of A- and C-quadrant identities with a possible trans-fate switch to a D-quadrant identity. 2) Treatment after the birth of micromere 4d induced formation of a third ectopic brain lobe, eye, and foregut lobe, which we interpret as a trans-fate switch of B-quadrant micromeres to a C-quadrant identity. 3) Continuous BMP treatment from late cleavage (4d + 12 h) through mid-larval stages resulted in a modest expansion of Ct-chrdl expression in the dorsal ectoderm and a concomitant loss of the ventral midline (neurotroch ciliary band). Loss of the ventral midline was accompanied by a collapse of the bilaterally-symmetric ventral nerve cord, although the total amount of neural tissue was not greatly affected. Our results compared with those from other annelids and molluscs suggest that BMP signaling was not ancestrally involved in delimiting neural tissue to one region of the D-V axis. However, the effects of ectopic BMP on quadrant-identity during cleavage stages may represent a non-axial organizing signal that was present in the last common ancestor of annelids and mollusks. Furthermore, in the last common ancestor of annelids, BMP signaling may have functioned in patterning ectodermal fates along the D-V axis in the trunk. Ultimately, studies on a wider range of spiralian taxa are needed to determine the role of BMP signaling during neural induction and neural patterning in the last common ancestor of this group. Ultimately, these comparisons will give us insight into the evolutionary origins of centralized nervous systems and body plans.
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Affiliation(s)
- Nicole B Webster
- Clark University Biology Department, 950 Main Street, Worcester, MA, 01610, USA.
| | - Michele Corbet
- Clark University Biology Department, 950 Main Street, Worcester, MA, 01610, USA
| | - Abhinav Sur
- Clark University Biology Department, 950 Main Street, Worcester, MA, 01610, USA
| | - Néva P Meyer
- Clark University Biology Department, 950 Main Street, Worcester, MA, 01610, USA.
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Lanza AR, Seaver EC. Functional evidence that Activin/Nodal signaling is required for establishing the dorsal-ventral axis in the annelid Capitella teleta. Development 2020; 147:147/18/dev189373. [PMID: 32967906 PMCID: PMC7522025 DOI: 10.1242/dev.189373] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 08/06/2020] [Indexed: 12/25/2022]
Abstract
The TGF-β superfamily comprises two distinct branches: the Activin/Nodal and BMP pathways. During development, signaling by this superfamily regulates a variety of embryological processes, and it has a conserved role in patterning the dorsal-ventral body axis. Recent studies show that BMP signaling establishes the dorsal-ventral axis in some mollusks. However, previous pharmacological inhibition studies in the annelid Capitella teleta, a sister clade to the mollusks, suggests that the dorsal-ventral axis is patterned via Activin/Nodal signaling. Here, we determine the role of both the Activin/Nodal and BMP pathways as they function in Capitella axis patterning. Antisense morpholino oligonucleotides were targeted to Ct-Smad2/3 and Ct-Smad1/5/8, transcription factors specific to the Activin/Nodal and BMP pathways, respectively. Following microinjection of zygotes, resulting morphant larvae were scored for axial anomalies. We demonstrate that the Activin/Nodal pathway of the TGF-β superfamily, but not the BMP pathway, is the primary dorsal-ventral patterning signal in Capitella. These results demonstrate variation in the molecular control of axis patterning across spiralians, despite sharing a conserved cleavage program. We suggest that these findings represent an example of developmental system drift. Summary: Morpholino knockdown experiments in the annelid Capitella teleta demonstrate that the dorsal-ventral axis is primarily patterned by the Activin/Nodal pathway of the TGF-β superfamily, rather than by the BMP pathway.
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Affiliation(s)
- Alexis R Lanza
- Whitney Laboratory for Marine Bioscience, University of Florida, 9505 Ocean Shore Boulevard, St Augustine, FL 32080-8610, USA
| | - Elaine C Seaver
- Whitney Laboratory for Marine Bioscience, University of Florida, 9505 Ocean Shore Boulevard, St Augustine, FL 32080-8610, USA
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Kumar S, Tumu SC, Helm C, Hausen H. The development of early pioneer neurons in the annelid Malacoceros fuliginosus. BMC Evol Biol 2020; 20:117. [PMID: 32928118 PMCID: PMC7489019 DOI: 10.1186/s12862-020-01680-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 08/27/2020] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Nervous system development is an interplay of many processes: the formation of individual neurons, which depends on whole-body and local patterning processes, and the coordinated growth of neurites and synapse formation. While knowledge of neural patterning in several animal groups is increasing, data on pioneer neurons that create the early axonal scaffold are scarce. Here we studied the first steps of nervous system development in the annelid Malacoceros fuliginosus. RESULTS We performed a dense expression profiling of a broad set of neural genes. We found that SoxB expression begins at 4 h postfertilization, and shortly later, the neuronal progenitors can be identified at the anterior and the posterior pole by the transient and dynamic expression of proneural genes. At 9 hpf, the first neuronal cells start differentiating, and we provide a detailed description of axonal outgrowth of the pioneer neurons that create the primary neuronal scaffold. Tracing back the clonal origin of the ventral nerve cord pioneer neuron revealed that it is a descendant of the blastomere 2d (2d221), which after 7 cleavages starts expressing Neurogenin, Acheate-Scute and NeuroD. CONCLUSIONS We propose that an anterior and posterior origin of the nervous system is ancestral in annelids. We suggest that closer examination of the first pioneer neurons will be valuable in better understanding of nervous system development in spirally cleaving animals, to determine the potential role of cell-intrinsic properties in neuronal specification and to resolve the evolution of nervous systems.
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Affiliation(s)
- Suman Kumar
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Sharat Chandra Tumu
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Conrad Helm
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway.,Present Address: Johann-Friedrich-Blumenbach Institute for Zoology and Anthropology, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Harald Hausen
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway.
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Sur A, Renfro A, Bergmann PJ, Meyer NP. Investigating cellular and molecular mechanisms of neurogenesis in Capitella teleta sheds light on the ancestor of Annelida. BMC Evol Biol 2020; 20:84. [PMID: 32664907 PMCID: PMC7362552 DOI: 10.1186/s12862-020-01636-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 06/03/2020] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Diverse architectures of nervous systems (NSs) such as a plexus in cnidarians or a more centralized nervous system (CNS) in insects and vertebrates are present across Metazoa, but it is unclear what selection pressures drove evolution and diversification of NSs. One underlying aspect of this diversity lies in the cellular and molecular mechanisms driving neurogenesis, i.e. generation of neurons from neural precursor cells (NPCs). In cnidarians, vertebrates, and arthropods, homologs of SoxB and bHLH proneural genes control different steps of neurogenesis, suggesting that some neurogenic mechanisms may be conserved. However, data are lacking for spiralian taxa. RESULTS To that end, we characterized NPCs and their daughters at different stages of neurogenesis in the spiralian annelid Capitella teleta. We assessed cellular division patterns in the neuroectoderm using static and pulse-chase labeling with thymidine analogs (EdU and BrdU), which enabled identification of NPCs that underwent multiple rounds of division. Actively-dividing brain NPCs were found to be apically-localized, whereas actively-dividing NPCs for the ventral nerve cord (VNC) were found apically, basally, and closer to the ventral midline. We used lineage tracing to characterize the changing boundary of the trunk neuroectoderm. Finally, to start to generate a genetic hierarchy, we performed double-fluorescent in-situ hybridization (FISH) and single-FISH plus EdU labeling for neurogenic gene homologs. In the brain and VNC, Ct-soxB1 and Ct-neurogenin were expressed in a large proportion of apically-localized, EdU+ NPCs. In contrast, Ct-ash1 was expressed in a small subset of apically-localized, EdU+ NPCs and subsurface, EdU- cells, but not in Ct-neuroD+ or Ct-elav1+ cells, which also were subsurface. CONCLUSIONS Our data suggest a putative genetic hierarchy with Ct-soxB1 and Ct-neurogenin at the top, followed by Ct-ash1, then Ct-neuroD, and finally Ct-elav1. Comparison of our data with that from Platynereis dumerilii revealed expression of neurogenin homologs in proliferating NPCs in annelids, which appears different than the expression of vertebrate neurogenin homologs in cells that are exiting the cell cycle. Furthermore, differences between neurogenesis in the head versus trunk of C. teleta suggest that these two tissues may be independent developmental modules, possibly with differing evolutionary trajectories.
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Affiliation(s)
- A. Sur
- Department of Biology, Clark University, 950 Main Street, Worcester, MA 01610 USA
| | - A. Renfro
- Department of Biology, Clark University, 950 Main Street, Worcester, MA 01610 USA
| | - P. J. Bergmann
- Department of Biology, Clark University, 950 Main Street, Worcester, MA 01610 USA
| | - N. P. Meyer
- Department of Biology, Clark University, 950 Main Street, Worcester, MA 01610 USA
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Kostyuchenko RP, Kozin VV. Morphallaxis versus Epimorphosis? Cellular and Molecular Aspects of Regeneration and Asexual Reproduction in Annelids. BIOL BULL+ 2020. [DOI: 10.1134/s1062359020030048] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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11
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Lyons DC, Perry KJ, Batzel G, Henry JQ. BMP signaling plays a role in anterior-neural/head development, but not organizer activity, in the gastropod Crepidula fornicata. Dev Biol 2020; 463:135-157. [PMID: 32389712 DOI: 10.1016/j.ydbio.2020.04.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 04/21/2020] [Accepted: 04/23/2020] [Indexed: 02/06/2023]
Abstract
BMP signaling is involved in many aspects of metazoan development, with two of the most conserved functions being to pattern the dorsal-ventral axis and to specify neural versus epidermal fates. An active area of research within developmental biology asks how BMP signaling was modified over evolution to build disparate body plans. Animals belonging to the superclade Spiralia/Lophotrochozoa are excellent experimental subjects for studying the evolution of BMP signaling because a highly conserved, stereotyped early cleavage program precedes the emergence of distinct body plans. In this study we examine the role of BMP signaling in one representative, the slipper snail Crepidula fornicata. We find that mRNAs encoding BMP pathway components (including the BMP ligand decapentaplegic, and BMP antagonists chordin and noggin-like proteins) are not asymmetrically localized along the dorsal-ventral axis in the early embryo, as they are in other species. Furthermore, when BMP signaling is perturbed by adding ectopic recombinant BMP4 protein, or by treating embryos with the selective Activin receptor-like kinase-2 (ALK-2) inhibitor Dorsomorphin Homolog 1 (DMH1), we observe no obvious effects on dorsal-ventral patterning within the posterior (post-trochal) region of the embryo. Instead, we see effects on head development and the balance between neural and epidermal fates specifically within the anterior, pre-trochal tissue derived from the 1q1 lineage. Our experiments define a window of BMP signaling sensitivity that ends at approximately 44-48 hours post fertilization, which occurs well after organizer activity has ended and after the dorsal-ventral axis has been determined. When embryos were exposed to BMP4 protein during this window, we observed morphogenetic defects leading to the separation of the anterior, 1q lineage from the rest of the embryo. The 1q-derived organoid remained largely undifferentiated and was radialized, while the post-trochal portion of the embryo developed relatively normally and exhibited clear signs of dorsal-ventral patterning. When embryos were exposed to DMH1 during the same time interval, we observed defects in the head, including protrusion of the apical plate, enlarged cerebral ganglia and ectopic ocelli, but otherwise the larvae appeared normal. No defects in shell development were noted following DMH1 treatments. The varied roles of BMP signaling in the development of several other spiralians have recently been examined. We discuss our results in this context, and highlight the diversity of developmental mechanisms within spiral-cleaving animals.
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Affiliation(s)
- Deirdre C Lyons
- Scripps Institution of Oceanography, U.C. San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.
| | - Kimberly J Perry
- University of Illinois, Department of Cell & Developmental Biology, 601 S. Goodwin Ave., Urbana, IL, 61801, USA
| | - Grant Batzel
- Scripps Institution of Oceanography, U.C. San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA
| | - Jonathan Q Henry
- University of Illinois, Department of Cell & Developmental Biology, 601 S. Goodwin Ave., Urbana, IL, 61801, USA.
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