Gene expression during echinoderm metamorphosis

Zygote ◽  
1999 ◽  
Vol 8 (S1) ◽  
pp. S48-S49
Author(s):  
Gregory A. Wray
Keyword(s):  
Sea Urchins ◽  
Cell Types ◽  
Small Populations ◽  
Important Process ◽  
Structural Genes ◽  
Planktonic Larva ◽  
Anatomical Changes ◽  
Preparatory Phase ◽  
Swimming Larva ◽  
Complete Process

Metamorphosis is a remarkable process in echinoderms, transforming a bilaterally symmetrical planktonic larva into a radially symmetrical benthic adult. This shift in habitat involves functional and anatomical changes in virtually every organ system (Bury, 1895; MacBride, 1914; Okazaki, 1975). Although metamorphosis is a crucial process in echinoderm development, we know relatively little about it. Furthermore, most of what we do know concerns sea urchins, and even less information is available about metamorphosis in other echinoderms. We have examined the expression of regulatory and structural genes during metamorphosis in several different echinoderm species (Lowe & Wray, 1997 and unpublished results). These data, together with those from several recent studies concerning additional genes (reviewed in Wray & Lowe, 2000), are beginning to shed new light on this complex and important process in echinoderm development.The overt transformation from swimming larva to settled juvenile is quite rapid in echinoderms (Cameron & Hinegardner, 1978), requiring less than half an hour in many species. The complete process of metamorphosis takes much longer, however (Okazaki, 1975; Gosselin & Jangoux, 1998). Extensive preparations begin several days to weeks before settlement (MacBride, 1914; Okazaki, 1975), depending upon the species and upon environmental conditions (Strathmann et al., 1992). During this preparatory phase, initially small populations of ectodermal and mesodermal cells fated to become the adult proliferate, differentiate and undergo complex morphogenetic movements to form the imaginal rudiment (MacBride, 1914; Okazaki, 1975). The rudiment is more complex than the larva in several important ways: it contains a greater number of cell types, it is the first place where true tissues form, and it contains the first well-organised nervous system (Okazaki, 1975; Chia & Burke, 1978).

scholarly journals Single cell RNA sequencing of the Strongylocentrotus purpuratus larva reveals the blueprint of major cell types and nervous system of a non-chordate deuterostome

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Periklis Paganos ◽  
Danila Voronov ◽  
Jacob M Musser ◽  
Detlev Arendt ◽  
Maria Ina Arnone
Keyword(s):  
Single Cell ◽  
Rna Sequencing ◽  
Sea Urchin ◽  
Regulatory Networks ◽  
Sea Urchins ◽  
Neuronal Cell ◽  
Cell Types ◽  
Molecular Fingerprint ◽  
Larval Body ◽  
Single Cell Rna Sequencing

Identifying the molecular fingerprint of organismal cell types is key for understanding their function and evolution. Here, we use single cell RNA sequencing (scRNA-seq) to survey the cell types of the sea urchin early pluteus larva, representing an important developmental transition from non-feeding to feeding larva. We identify 21 distinct cell clusters, representing cells of the digestive, skeletal, immune, and nervous systems. Further subclustering of these reveal a highly detailed portrait of cell diversity across the larva, including the identification of neuronal cell types. We then validate important gene regulatory networks driving sea urchin development and reveal new domains of activity within the larval body. Focusing on neurons that co-express Pdx-1 and Brn1/2/4, we identify an unprecedented number of genes shared by this population of neurons in sea urchin and vertebrate endocrine pancreatic cells. Using differential expression results from Pdx-1 knockdown experiments, we show that Pdx1 is necessary for the acquisition of the neuronal identity of these cells. We hypothesize that a network similar to the one orchestrated by Pdx1 in the sea urchin neurons was active in an ancestral cell type and then inherited by neuronal and pancreatic developmental lineages in sea urchins and vertebrates.

scholarly journals Hydrozoan sperm-specific H2B histone variants stabilize chromatin and block transcription without enhancing chromatin condensation

2021 ◽  
Author(s):  
Anna Torok ◽  
Martin JG Browne ◽  
Jordina C Vilar ◽  
Indu Patwal ◽  
Timothy Q DuBuc ◽  
...  
Keyword(s):  
Sea Urchins ◽  
Chromatin Condensation ◽  
Ectopic Expression ◽  
Cell Types ◽  
Histone Variants ◽  
Sperm Chromatin ◽  
Chromatin Compaction ◽  
Cycle Arrest

Many animals achieve sperm chromatin compaction and stabilisation during spermatogenesis by replacing canonical histones with sperm nuclear basic proteins (SNBPs) such as protamines. A number of animals including hydrozoan cnidarians and echinoid sea urchins lack protamines and have instead evolved a distinctive family of sperm-specific histone H2Bs (spH2Bs) with extended N-termini rich in SPKK-related motifs. Sperm packaging in echinoids such as sea urchins is regulated by spH2Bs and their sperm is negatively buoyant for fertilization on the sea floor. Hydroid cnidarians also package sperm with spH2Bs but undertake broadcast spawning and their sperm properties are poorly characterised. We show that sperm chromatin from the hydroid Hydractinia possesses higher stability than its somatic equivalent, with reduced accessibility of sperm chromatin to transposase Tn5 integration in vivo and to endonucleases in vitro. However, nuclear dimensions are only moderately reduced in mature Hydractinia sperm compared to other cell types. Ectopic expression of spH2B in the background of H2B knockdown resulted in downregulation of global transcription and cell cycle arrest in embryos without altering their nuclear density. Taken together, spH2B variants containing SPKK-related motifs act to stabilise chromatin and silence transcription in Hydractinia sperm without significant chromatin compaction. This is consistent with a contribution of spH2B to sperm buoyancy as a reproductive adaptation.

scholarly journals Functional and anatomical relationships between the medial precentral cortex, dorsal striatum, and head direction cell circuitry. II. Neuroanatomical studies

2019 ◽  
Vol 121 (2) ◽  
pp. 371-395 ◽  
Author(s):  
Max L. Mehlman ◽  
Shawn S. Winter ◽  
Jeffrey S. Taube
Keyword(s):  
Limbic System ◽  
Dorsal Striatum ◽  
Cell Types ◽  
Spatial Processing ◽  
Small Populations ◽  
Head Direction ◽  
Functional Relationships ◽  
Anatomical Basis ◽  
Direct Input ◽  
Self Motion

An animal’s directional heading within its environment is encoded by the activity of head direction (HD) cells. In rodents, these neurons are found primarily within the limbic system in the interconnected structures that form the limbic HD circuit. In our accompanying report in this issue, we describe two HD cell populations located outside of this circuit in the medial precentral cortex (PrCM) and dorsal striatum (DS). These extralimbic areas receive their HD signals from the limbic system but do not provide critical input or feedback to limbic HD cells (Mehlman ML, Winter SS, Valerio S, Taube JS. J Neurophysiol 121: 350–370, 2019.). In this report, we complement our previous lesion and recording experiments with a series of neuroanatomical tracing studies in rats designed to examine patterns of connectivity between the PrCM, DS, limbic HD circuit, and related spatial processing circuitry. Retrograde tracing revealed that the DS receives direct input from numerous structures known to contain HD cells and/or other spatially tuned cell types. Importantly, these projections preferentially target and converge within the most medial portion of the DS, the same area in which we previously recorded HD cells. The PrCM receives direct input from a subset of these spatial processing structures. Anterograde tracing identified indirect pathways that could permit the PrCM and DS to convey self-motion information to the limbic HD circuit. These tracing studies reveal the anatomical basis for the functional relationships observed in our lesion and recording experiments. Collectively, these findings expand our understanding of how spatial processing circuitry functionally and anatomically extends beyond the limbic system into the PrCM and DS. NEW & NOTEWORTHY Head direction (HD) cells are located primarily within the limbic system, but small populations of extralimbic HD cells are found in the medial precentral cortex (PrCM) and dorsal striatum (DS). The neuroanatomical tracing experiments reported here explored the pathways capable of transmitting the HD signal to these extralimbic areas. We found that projections arising from numerous spatial processing structures converge within portions of the PrCM and DS that contain HD cells.

scholarly journals Ciliary and rhabdomeric photoreceptor-cell circuits form a spectral depth gauge in marine zooplankton

2018 ◽  
Author(s):  
Csaba Verasztó ◽  
Martin Gühmann ◽  
Huiyong Jia ◽  
Vinoth Babu Veedin Rajan ◽  
Luis A. Bezares-Calderón ◽  
...  
Keyword(s):  
Photoreceptor Cell ◽  
Uv Light ◽  
Functional Integration ◽  
Photoreceptor Cells ◽  
Cell Types ◽  
Planktonic Larva ◽  
Marine Zooplankton ◽  
Rhabdomeric Photoreceptor ◽  
Depth Gauge ◽  
Rhabdomeric Photoreceptor Cells

AbstractCiliary and rhabdomeric photoreceptor cells represent two main lines of photoreceptor evolution in animals. The two photoreceptor-cell types coexist in some animals, however how they functionally integrate is unknown. We used connectomics to map synaptic paths between ciliary and rhabdomeric photoreceptors in the planktonic larva of the annelid Platynereis and found that ciliary photoreceptors are presynaptic to the rhabdomeric circuit. The behaviors mediated by the ciliary and rhabdomeric cells also interact hierarchically. The ciliary photoreceptors are UV-sensitive and mediate downward swimming to non-directional UV light, a behavior absent in ciliary-opsin knockouts. UV avoidance antagonizes positive phototaxis mediated by the rhabdomeric eyes so that vertical swimming direction is determined by the ratio of blue/UV light. Since this ratio increases with depth, Platynereis larvae may use it as a depth gauge during planktonic migration. Our results revealed a functional integration of ciliary and rhabdomeric photoreceptors with implications for eye and photoreceptor evolution.

Presence and distribution of specific prosome antigens change as a function of embryonic development and tissue-type differentiation in Pleurodeles waltl

1988 ◽  
Vol 90 (4) ◽  
pp. 555-567 ◽  
Author(s):  
J.K. Pal ◽  
P. Gounon ◽  
M.F. Grossi de Sa ◽  
K. Scherrer
Keyword(s):  
Protein Complexes ◽  
Cell Types ◽  
Immunoblot Analysis ◽  
Tissue Type ◽  
Animal Pole ◽  
Development And Differentiation ◽  
A Cell ◽  
Pleurodeles Waltl ◽  
Rna Protein Complexes ◽  
Swimming Larva

The prosomes, biochemically well characterized small RNA-protein complexes, found associated with mRNA in all eukaryotic cells tested, have been identified as maternal components in sea urchin and chick embryos. In this study, we investigated their presence and cytolocalization in the oocytes and embryos of Pleurodeles waltl by immunoblot analysis and immunofluorescence, using monoclonal antibodies prepared against duck prosome proteins. Of the four antibodies tested, three recognized the corresponding antigens in oocyte total protein extracts. Immunofluorescence analysis, using the three prosomal antibodies, demonstrated a drastic change in the localization of the prosome antigens, which changed from the cytoplasm to the nucleus during oogenesis. In the nucleus, in diplotene stages, prosomal antigens appeared to be associated with the lampbrush chromosomes and the nuclear matrix. During embryogenesis, the subcellular distribution of the prosome antigens was a function of development and differentiation: in the cleavage stages up to the mid-blastula they were localized in the cytoplasm and on the plasma membrane, while in the late blastula, gastrula and neurula they were in the nucleus. Interestingly, one of the prosome antigens, p31K, was found to be in a different location in certain cells in the animal pole of the mid-blastula and was absent in the neural tissue in the neurula. In still later stages, in the free-swimming larva, all three antigens were localized in the cytoplasm, specifically in certain cell types in the epidermal tissues. Furthermore, they were sectorially distributed in the cytoplasm. These data taken together indicate the possible presence of tissue-type-specific prosome antigens in Pleurodeles. Differentiation-dependent subcellular localization of the prosome antigens suggests a cell-compartment-related multiple function of prosomes.

scholarly journals Developmental gene regulatory networks in sea urchins and what we can learn from them

F1000Research ◽  
2016 ◽  
Vol 5 ◽  
pp. 203 ◽  
Author(s):  
Megan L. Martik ◽  
Deirdre C. Lyons ◽  
David R. McClay
Keyword(s):  
Transcription Factors ◽  
Gene Regulatory Network ◽  
Sea Urchin ◽  
Network Model ◽  
Regulatory Network ◽  
Regulatory Networks ◽  
Sea Urchins ◽  
Cell Types ◽  
Zygotic Transcription ◽  
Gene Regulatory

Sea urchin embryos begin zygotic transcription shortly after the egg is fertilized.  Throughout the cleavage stages a series of transcription factors are activated and, along with signaling through a number of pathways, at least 15 different cell types are specified by the beginning of gastrulation.  Experimentally, perturbation of contributing transcription factors, signals and receptors and their molecular consequences enabled the assembly of an extensive gene regulatory network model.  That effort, pioneered and led by Eric Davidson and his laboratory, with many additional insights provided by other laboratories, provided the sea urchin community with a valuable resource.  Here we describe the approaches used to enable the assembly of an advanced gene regulatory network model describing molecular diversification during early development.  We then provide examples to show how a relatively advanced authenticated network can be used as a tool for discovery of how diverse developmental mechanisms are controlled and work.

The origin of spicule-forming cells in a ‘primitive’ sea urchin (Eucidaris tribuloides) which appears to lack primary mesenchyme cells

Development ◽  
1988 ◽  
Vol 103 (2) ◽  
pp. 305-315 ◽  
Author(s):  
G.A. Wray ◽  
D.R. McClay
Keyword(s):  
Sea Urchin ◽  
Sea Urchins ◽  
Cell Lineage ◽  
Cell Types ◽  
Morphological Evidence ◽  
Specific Gene ◽  
Apparent Paradox ◽  
Mesenchyme Cells ◽  
Lineage Specific Gene ◽  
Primary Mesenchyme Cells

The calcareous larval skeleton of euechinoid sea urchins is synthesized by primary mesenchyme cells which ingress prior to gastrulation. In embryos of the cidaroid sea urchin Eucidaris tribuloides, no mesenchyme cells ingress before gastrulation, yet larvae later contain skeletons. This apparent paradox is resolved by immunochemical, cell lineage and morphological evidence showing that spicule-forming cells of Eucidaris are homologous to primary mesenchyme cells of euechinoids. In particular, these two cell types share expression of two cell lineage-specific gene products, are derived from the same cellular precursors, the micromeres, and undergo a similar migratory phase prior to skeletogenesis. Despite these similarities, there are far fewer spicule-forming cells in Eucidaris than in typical euechinoids and they assume a different pattern during spiculogenesis. The homology between Eucidaris spicule-forming cells and euechinoid primary mesenchyme cells indicates that a heterochrony in the time of spicule-forming cell ingression has occurred since the divergence of their respective lineages.

scholarly journals Ciliary and rhabdomeric photoreceptor-cell circuits form a spectral depth gauge in marine zooplankton

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Csaba Verasztó ◽  
Martin Gühmann ◽  
Huiyong Jia ◽  
Vinoth Babu Veedin Rajan ◽  
Luis A Bezares-Calderón ◽  
...  
Keyword(s):  
Photoreceptor Cell ◽  
Uv Light ◽  
Functional Integration ◽  
Photoreceptor Cells ◽  
Cell Types ◽  
Planktonic Larva ◽  
Marine Zooplankton ◽  
Rhabdomeric Photoreceptor ◽  
Depth Gauge ◽  
Rhabdomeric Photoreceptor Cells

Ciliary and rhabdomeric photoreceptor cells represent two main lines of photoreceptor-cell evolution in animals. The two cell types coexist in some animals, however how these cells functionally integrate is unknown. We used connectomics to map synaptic paths between ciliary and rhabdomeric photoreceptors in the planktonic larva of the annelid Platynereis and found that ciliary photoreceptors are presynaptic to the rhabdomeric circuit. The behaviors mediated by the ciliary and rhabdomeric cells also interact hierarchically. The ciliary photoreceptors are UV-sensitive and mediate downward swimming in non-directional UV light, a behavior absent in ciliary-opsin knockout larvae. UV avoidance overrides positive phototaxis mediated by the rhabdomeric eyes such that vertical swimming direction is determined by the ratio of blue/UV light. Since this ratio increases with depth, Platynereis larvae may use it as a depth gauge during vertical migration. Our results revealed a functional integration of ciliary and rhabdomeric photoreceptor cells in a zooplankton larva.

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