The Experts below are selected from a list of 927 Experts worldwide ranked by ideXlab platform
Bernd Schierwater - One of the best experts on this subject based on the ideXlab platform.
-
Additional file 1: of Innate immunity in the simplest animals â placozoans
2019Co-Authors: Kai Kamm, Bernd Schierwater, Rob DesalleAbstract:Figure S1. TIR/SEFIR-domain containing proteins in Trichoplax sp. H2. Table S1. Possible candidates for the extracellular part of a hypothetical bipartite TLR-like receptor in Trichoplax sp. H2. Table S2. The TLR pathway related gene repertoire in Trichoplax sp. H2 apart from TIR-domain containing genes. (PDF 83 kb
-
Additional file 4: of Innate immunity in the simplest animals â placozoans
2019Co-Authors: Kai Kamm, Bernd Schierwater, Rob DesalleAbstract:Dataset S3. Spreadsheet containing the protein domain summary and the locus_tags of: A The Trichoplax sp. H2 scavenger receptors B The Trichoplax sp. H2 arrestins C The Trichoplax sp. H2 lectin-like secreted proteins (CTLD, FReD or C1q containing) D The Trichoplax sp. H2 NOD-like receptors. (XLSX 32 kb
-
Innate immunity in the simplest animals – placozoans
BMC, 2019Co-Authors: Kai Kamm, Bernd Schierwater, Rob DesalleAbstract:Abstract Background Innate immunity provides the core recognition system in animals for preventing infection, but also plays an important role in managing the relationship between an animal host and its symbiont. Most of our knowledge about innate immunity stems from a few animal model systems, but substantial variation between metazoan phyla has been revealed by comparative genomic studies. The exploration of more taxa is still needed to better understand the evolution of immunity related mechanisms. Placozoans are morphologically the simplest organized metazoans and the association between these enigmatic animals and their rickettsial endosymbionts has recently been elucidated. Our analyses of the novel placozoan nuclear genome of Trichoplax sp. H2 and its associated rickettsial endosymbiont genome clearly pointed to a mutualistic and co-evolutionary relationship. This discovery raises the question of how the placozoan holobiont manages symbiosis and, conversely, how it defends against harmful microorganisms. In this study, we examined the annotated genome of Trichoplax sp. H2 for the presence of genes involved in innate immune recognition and downstream signaling. Results A rich repertoire of genes belonging to the Toll-like and NOD-like receptor pathways, to scavenger receptors and to secreted fibrinogen-related domain genes was identified in the genome of Trichoplax sp. H2. Nevertheless, the innate immunity related pathways in placozoans deviate in several instances from well investigated vertebrates and invertebrates. While true Toll- and NOD-like receptors are absent, the presence of many genes of the downstream signaling cascade suggests at least primordial Toll-like receptor signaling in Placozoa. An abundance of scavenger receptors, fibrinogen-related domain genes and Apaf-1 genes clearly constitutes an expansion of the immunity related gene repertoire specific to Placozoa. Conclusions The found wealth of immunity related genes present in Placozoa is surprising and quite striking in light of the extremely simple placozoan body plan and their sparse cell type makeup. Research is warranted to reveal how Placozoa utilize this immune repertoire to manage and maintain their associated microbiota as well as to fend-off pathogens
-
Trichoplax genomes reveal profound admixture and suggest stable wild populations without bisexual reproduction.
Scientific reports, 2018Co-Authors: Kai Kamm, Peter F. Stadler, Hans-jürgen Osigus, Rob Desalle, Bernd SchierwaterAbstract:The phylum Placozoa officially consists of only a single described species, Trichoplax adhaerens, although several lineages can be separated by molecular markers, geographical distributions and environmental demands. The placozoan 16S haplotype H2 (Trichoplax sp. H2) is the most robust and cosmopolitan lineage of placozoans found to date. In this study, its genome was found to be distinct but highly related to the Trichoplax adhaerens reference genome, for remarkably unique reasons. The pattern of variation and allele distribution between the two lineages suggests that both originate from a single interbreeding event in the wild, dating back at least several decades ago, and both seem not to have engaged in sexual reproduction since. We conclude that populations of certain placozoan haplotypes remain stable for long periods without bisexual reproduction. Furthermore, allelic variation within and between the two Trichoplax lineages indicates that successful bisexual reproduction between related placozoan lineages might serve to either counter accumulated negative somatic mutations or to cope with changing environmental conditions. On the other hand, enrichment of neutral or beneficial somatic mutations by vegetative reproduction, combined with rare sexual reproduction, could instantaneously boost genetic variation, generating novel ecotypes and eventually species.
-
Molecular 16S rDNA diagnostics for the genera Hoilungia and Trichoplax.
2018Co-Authors: Michael Eitel, Frederique Varoqueaux, Hans-jürgen Osigus, Warren R. Francis, Jean Daraspe, Stefan Krebs, Sergio Vargas, Helmut Blum, Gray A. Williams, Bernd SchierwaterAbstract:Molecular 16S rDNA diagnostics for the genera Hoilungia and Trichoplax.
Carolyn L Smith - One of the best experts on this subject based on the ideXlab platform.
-
early metazoan origin and multiple losses of a novel clade of rim presynaptic calcium channel scaffolding protein homologs
Genome Biology and Evolution, 2020Co-Authors: Thomas Piekut, Carolyn L Smith, Julia Gauberg, Alicia N. Harracksingh, Yuen Yan Wong, Sarah E Walker, Christopher Lowden, Haiying M Cheng, Brian B Novogradac, Gaynor E SpencerAbstract:The precise localization of CaV2 voltage-gated calcium channels at the synapse active zone requires various interacting proteins, of which, Rab3-interacting molecule or RIM is considered particularly important. In vertebrates, RIM interacts with CaV2 channels in vitro via a PDZ domain that binds to the extreme C-termini of the channels at acidic ligand motifs of D/E-D/E/H-WC-COOH, and knockout of RIM in vertebrates and invertebrates disrupts CaV2 channel synaptic localization and synapse function. Here, we describe a previously uncharacterized clade of RIM proteins bearing domain architectures homologous to those of known RIM homologs, but with some notable differences including key amino acids associated with PDZ domain ligand specificity. This novel RIM emerged near the stem lineage of metazoans and underwent extensive losses, but is retained in select animals including the early-diverging placozoan Trichoplax adhaerens, and molluscs. RNA expression and localization studies in Trichoplax and the mollusc snail Lymnaea stagnalis indicate differential regional/tissue type expression, but overlapping expression in single isolated neurons from Lymnaea. Ctenophores, the most early-diverging animals with synapses, are unique among animals with nervous systems in that they lack the canonical RIM, bearing only the newly identified homolog. Through phylogenetic analysis, we find that CaV2 channel D/E-D/E/H-WC-COOH like PDZ ligand motifs were present in the common ancestor of cnidarians and bilaterians, and delineate some deeply conserved C-terminal structures that distinguish CaV1 from CaV2 channels, and CaV1/CaV2 from CaV3 channels.
-
early metazoan origin and multiple losses of a novel clade of rim pre synaptic calcium channel scaffolding protein homologues
bioRxiv, 2020Co-Authors: Thomas Piekut, Carolyn L Smith, Julia Gauberg, Alicia N. Harracksingh, Yuen Yan Wong, Sarah E Walker, Christopher Lowden, Haiying M Cheng, Gaynor E Spencer, Adriano SenatoreAbstract:The precise localization of CaV2 voltage-gated calcium channels at the synapse active zone requires various interacting proteins, of which, Rab3 interacting molecule or RIM is considered particularly important. In vertebrates, RIM interacts with CaV2 channels in vitro via a PDZ domain that binds to the extreme C-termini of the channels at acidic ligand motifs of D/E-D/E/H-WC-COOH, and knockout of RIM in vertebrates and invertebrates disrupts CaV2 channel synaptic localization and synapse function. Here, we describe a previously uncharacterized clade of RIM proteins bearing homologous domain architectures as known RIM homologues, but some notable differences including key amino acids associated with PDZ domain ligand specificity. This novel RIM emerged near the stem lineage of metazoans and underwent extensive losses, but is retained in select animals including the early-diverging placozoan Trichoplax adhaerens, and molluscs. RNA expression and localization studies in Trichoplax and the mollusc snail Lymnaea stagnalis indicate differential regional/tissue type expression, but overlapping expression in single isolated neurons from Lymnaea. Ctenophores, the most early-diverging animals with synapses, are unique among animals with nervous systems in that they lack the canonical RIM, bearing only the newly identified homologue. Through phylogenetic analysis, we find that CaV2 channel D/E-D/E/H-WC-COOH like PDZ ligand motifs were present the common ancestor of cnidarians and bilaterians. We also delineate some deeply conserved C-terminal structures that distinguish CaV1 from CaV2 channels, and CaV1/CaV2 from CaV3 channels.
-
Insights into the evolution of digestive systems from studies of Trichoplax adhaerens
Cell and Tissue Research, 2019Co-Authors: Carolyn L Smith, T. D. MayorovaAbstract:Trichoplax , a member of the phylum Placozoa, is a tiny ciliated marine animal that glides on surfaces feeding on algae and cyanobacteria. It stands out from other animals in that it lacks an internal digestive system and, instead, digests food trapped under its lower surface. Here we review recent work on the phenotypes of its six cell types and their roles in digestion and feeding behavior. Phylogenomic analyses place Placozoa as sister to Eumetazoa, the clade that includes Cnidaria and Bilateria. Comparing the phenotypes of cells in Trichoplax to those of cells in the digestive epithelia of Eumetazoa allows us to make inferences about the cell types and mode of feeding of their ancestors. From our increasingly mechanistic understanding of feeding in Trichoplax , we get a glimpse into how primitive animals may have hunted and consumed food prior to the evolution of neurons, muscles, and internal digestive systems.
-
The ventral epithelium of Trichoplax adhaerens deploys in distinct patterns cells that secrete digestive enzymes, mucus or diverse neuropeptides.
Biology open, 2019Co-Authors: Tatiana D. Mayorova, Thomas S. Reese, Katherine Hammar, Christine A. Winters, Carolyn L SmithAbstract:The disk-shaped millimeter-sized marine animal, Trichoplax adhaerens, is notable because of its small number of cell types and primitive mode of feeding. It glides on substrates propelled by beating cilia on its lower surface and periodically pauses to feed on underlying microorganisms, which it digests externally. Here, a combination of advanced electron and light microscopic techniques are used to take a closer look at its secretory cell types and their roles in locomotion and feeding. We identify digestive enzymes in lipophils, a cell type implicated in external digestion and distributed uniformly throughout the ventral epithelium except for a narrow zone near its edge. We find three morphologically distinct types of gland cell. The most prevalent contains and secretes mucus, which is shown to be involved in adhesion and gliding. Half of the mucocytes are arrayed in a tight row around the edge of the ventral epithelium while the rest are scattered further inside, in the region containing lipophils. The secretory granules in mucocytes at the edge label with an antibody against a neuropeptide that was reported to arrest ciliary beating during feeding. A second type of gland cell is arrayed in a narrow row just inside the row of mucocytes while a third is located more centrally. Our maps of the positions of the structurally distinct secretory cell types provide a foundation for further characterization of the multiple peptidergic cell types in Trichoplax and the microscopic techniques we introduce provide tools for carrying out these studies.
-
Cells containing aragonite crystals mediate responses to gravity in Trichoplax adhaerens (Placozoa), an animal lacking neurons and synapses.
PloS one, 2018Co-Authors: Tatiana D. Mayorova, Carolyn L Smith, Katherine Hammar, Christine A. Winters, Natalia B. Pivovarova, Maria A. Aronova, Richard D. Leapman, Thomas S. ReeseAbstract:Trichoplax adhaerens has only six cell types. The function as well as the structure of crystal cells, the least numerous cell type, presented an enigma. Crystal cells are arrayed around the perimeter of the animal and each contains a birefringent crystal. Crystal cells resemble lithocytes in other animals so we looked for evidence they are gravity sensors. Confocal microscopy showed that their cup-shaped nuclei are oriented toward the edge of the animal, and that the crystal shifts downward under the influence of gravity. Some animals spontaneously lack crystal cells and these animals behaved differently upon being tilted vertically than animals with a typical number of crystal cells. EM revealed crystal cell contacts with fiber cells and epithelial cells but these contacts lacked features of synapses. EM spectroscopic analyses showed that crystals consist of the aragonite form of calcium carbonate. We thus provide behavioral evidence that Trichoplax are able to sense gravity, and that crystal cells are likely to be their gravity receptors. Moreover, because placozoans are thought to have evolved during Ediacaran or Cryogenian eras associated with aragonite seas, and their crystals are made of aragonite, they may have acquired gravity sensors during this early era.
Thomas S. Reese - One of the best experts on this subject based on the ideXlab platform.
-
The ventral epithelium of Trichoplax adhaerens deploys in distinct patterns cells that secrete digestive enzymes, mucus or diverse neuropeptides.
Biology open, 2019Co-Authors: Tatiana D. Mayorova, Thomas S. Reese, Katherine Hammar, Christine A. Winters, Carolyn L SmithAbstract:The disk-shaped millimeter-sized marine animal, Trichoplax adhaerens, is notable because of its small number of cell types and primitive mode of feeding. It glides on substrates propelled by beating cilia on its lower surface and periodically pauses to feed on underlying microorganisms, which it digests externally. Here, a combination of advanced electron and light microscopic techniques are used to take a closer look at its secretory cell types and their roles in locomotion and feeding. We identify digestive enzymes in lipophils, a cell type implicated in external digestion and distributed uniformly throughout the ventral epithelium except for a narrow zone near its edge. We find three morphologically distinct types of gland cell. The most prevalent contains and secretes mucus, which is shown to be involved in adhesion and gliding. Half of the mucocytes are arrayed in a tight row around the edge of the ventral epithelium while the rest are scattered further inside, in the region containing lipophils. The secretory granules in mucocytes at the edge label with an antibody against a neuropeptide that was reported to arrest ciliary beating during feeding. A second type of gland cell is arrayed in a narrow row just inside the row of mucocytes while a third is located more centrally. Our maps of the positions of the structurally distinct secretory cell types provide a foundation for further characterization of the multiple peptidergic cell types in Trichoplax and the microscopic techniques we introduce provide tools for carrying out these studies.
-
Cells containing aragonite crystals mediate responses to gravity in Trichoplax adhaerens (Placozoa), an animal lacking neurons and synapses.
PloS one, 2018Co-Authors: Tatiana D. Mayorova, Carolyn L Smith, Katherine Hammar, Christine A. Winters, Natalia B. Pivovarova, Maria A. Aronova, Richard D. Leapman, Thomas S. ReeseAbstract:Trichoplax adhaerens has only six cell types. The function as well as the structure of crystal cells, the least numerous cell type, presented an enigma. Crystal cells are arrayed around the perimeter of the animal and each contains a birefringent crystal. Crystal cells resemble lithocytes in other animals so we looked for evidence they are gravity sensors. Confocal microscopy showed that their cup-shaped nuclei are oriented toward the edge of the animal, and that the crystal shifts downward under the influence of gravity. Some animals spontaneously lack crystal cells and these animals behaved differently upon being tilted vertically than animals with a typical number of crystal cells. EM revealed crystal cell contacts with fiber cells and epithelial cells but these contacts lacked features of synapses. EM spectroscopic analyses showed that crystals consist of the aragonite form of calcium carbonate. We thus provide behavioral evidence that Trichoplax are able to sense gravity, and that crystal cells are likely to be their gravity receptors. Moreover, because placozoans are thought to have evolved during Ediacaran or Cryogenian eras associated with aragonite seas, and their crystals are made of aragonite, they may have acquired gravity sensors during this early era.
-
How crystal cells may be activated when tilted.
2018Co-Authors: Tatiana D. Mayorova, Carolyn L Smith, Katherine Hammar, Christine A. Winters, Natalia B. Pivovarova, Maria A. Aronova, Richard D. Leapman, Thomas S. ReeseAbstract:Possible mechanism of selective crystal cell activation in Trichoplax upon being tilted vertically. Schematic cross-section of Trichoplax attached to horizontal (a) or vertical (b) substrates, and en face view of animal on a vertical substrate (c). Cup-shaped nuclei (blue) are directed to the edge of the animal, regardless of its orientation with respect to gravity, while crystals move under the influence of gravity. Crystals in animals on a horizontal surface (a) generally remain in the nuclear cup, but when the surface is tilted vertically (b), crystals on the down side of Trichoplax fall out of the cup (red outline). We postulate that pressure exerted by the crystal on the plasma membrane activates mechanosensitive receptors in the membrane, which in turn causes the crystal cell to transmit a signal (red brackets). En face view (c) illustrates the distribution of activated crystal cells (red outlines and brackets) in an animal on a vertical substrate.
-
Neuropeptidergic integration of behavior in Trichoplax adhaerens, an animal without synapses.
The Journal of experimental biology, 2017Co-Authors: Adriano Senatore, Thomas S. Reese, Carolyn L SmithAbstract:Trichoplax adhaerens is a flat, millimeter-sized marine animal that adheres to surfaces and grazes on algae. Trichoplax displays a repertoire of different feeding behaviors despite the apparent absence of a true nervous system with electrical or chemical synapses. It glides along surfaces to find food, propelled by beating cilia on cells at its ventral surface, and pauses during feeding by arresting ciliary beating. We found that when endomorphin-like peptides are applied to an animal, ciliary beating is arrested, mimicking natural feeding pauses. Antibodies against these neuropeptides label cells that express the neurosecretory proteins and voltage-gated calcium channels implicated in regulated secretion. These cells are embedded in the ventral epithelium, where they comprise only 4% of the total, and are concentrated around the edge of the animal. Each bears a cilium likely to be chemosensory and used to detect algae. Trichoplax pausing during feeding or spontaneously in the absence of food often induce their neighbors to pause as well, even neighbors not in direct contact. Pausing behavior propagates from animal to animal across distances much greater than the signal that diffuses from just one animal, so we presume that the peptides secreted from one animal elicit secretion from nearby animals. Signal amplification by peptide-induced peptide secretion explains how a small number of sensory secretory cells lacking processes and synapses can evoke a wave of peptide secretion across the entire animal to globally arrest ciliary beating and allow pausing during feeding.
-
RESEARCH ARTICLE Coordinated Feeding Behavior in Trichoplax, an Animal without Synapses
2016Co-Authors: Carolyn L Smith, Natalia Pivovarova, Thomas S. ReeseAbstract:Trichoplax is a small disk-shaped marine metazoan that adheres to substrates and loco-motes by ciliary gliding. Despite having only six cell types and lacking synapses Trichoplax coordinates a complex sequence of behaviors culminating in external digestion of algae. We combine live cell imaging with electron microscopy to show how this is accomplished. When Trichoplax glides over a patch of algae, its cilia stop beating so it ceases moving. A subset of one of the cell types, lipophils, simultaneously secretes granules whose content rapidly lyses algae. This secretion is accurately targeted, as only lipophils located near algae release granules. The animal pauses while the algal content is ingested, and then resumes gliding. Global control of gliding is coordinated with precise local control of lipophil secretion suggesting the presence of mechanisms for cellular communication and integration
Adriano Senatore - One of the best experts on this subject based on the ideXlab platform.
-
conserved biophysical features of the cav2 presynaptic ca2 channel homologue from the early diverging animal Trichoplax adhaerens
Journal of Biological Chemistry, 2020Co-Authors: Julia Gauberg, Wassim Elkhatib, Thomas Piekut, Salsabil Abdallah, Alicia N. Harracksingh, Elise F. Stanley, Adriano SenatoreAbstract:The dominant role of CaV2 voltage-gated calcium channels for driving neurotransmitter release is broadly conserved. Given the overlapping functional properties of CaV2 and CaV1 channels, and less so CaV3 channels, it is unclear why there have not been major shifts toward dependence on other CaV channels for synaptic transmission. Here, we provide a structural and functional profile of the CaV2 channel cloned from the early-diverging animal Trichoplax adhaerens, which lacks a nervous system but possesses single gene homologues for CaV1-CaV3 channels. Remarkably, the highly divergent channel possesses similar features as human CaV2.1 and other CaV2 channels, including high voltage-activated currents that are larger in external Ba2+ than in Ca2+; voltage-dependent kinetics of activation, inactivation, and deactivation; and bimodal recovery from inactivation. Altogether, the functional profile of Trichoplax CaV2 suggests that the core features of presynaptic CaV2 channels were established early during animal evolution, after CaV1 and CaV2 channels emerged via proposed gene duplication from an ancestral CaV1/2 type channel. The Trichoplax channel was relatively insensitive to mammalian CaV2 channel blockers ω-agatoxin-IVA and ω-conotoxin-GVIA and to metal cation blockers Cd2+ and Ni2+. Also absent was the capacity for voltage-dependent G-protein inhibition by co-expressed Trichoplax Gβγ subunits, which nevertheless inhibited the human CaV2.1 channel, suggesting that this modulatory capacity evolved via changes in channel sequence/structure, and not G proteins. Last, the Trichoplax channel was immunolocalized in cells that express an endomorphin-like peptide implicated in cell signaling and locomotive behavior and other likely secretory cells, suggesting contributions to regulated exocytosis.
-
Functional Studies of Trichoplax adhaerens Voltage-Gated Calcium Channel Activity.
Methods in molecular biology (Clifton N.J.), 2020Co-Authors: Julia Gauberg, Adriano Senatore, Andreas HeylandAbstract:Trichoplax adhaerens is a member of the phylum Placozoa, an enigmatic group of benthic animals with remarkably simple morphology. While initial work on these organisms has primarily focused on their morphology and the development of genomic resources, Trichoplax has received increased attention as a model for studying the evolution of nervous and sensory systems. This work is motivated by the fact that Trichoplax features distinct behaviours and responses to environmental stimuli. Therefore, much progress has been made in recent years on the molecular, cellular, and behavioral understanding of this organism. Methods outlined here provide hands-on approaches to cutting edge molecular and cellular techniques to record cellular activities in Trichoplax.
-
early metazoan origin and multiple losses of a novel clade of rim pre synaptic calcium channel scaffolding protein homologues
bioRxiv, 2020Co-Authors: Thomas Piekut, Carolyn L Smith, Julia Gauberg, Alicia N. Harracksingh, Yuen Yan Wong, Sarah E Walker, Christopher Lowden, Haiying M Cheng, Gaynor E Spencer, Adriano SenatoreAbstract:The precise localization of CaV2 voltage-gated calcium channels at the synapse active zone requires various interacting proteins, of which, Rab3 interacting molecule or RIM is considered particularly important. In vertebrates, RIM interacts with CaV2 channels in vitro via a PDZ domain that binds to the extreme C-termini of the channels at acidic ligand motifs of D/E-D/E/H-WC-COOH, and knockout of RIM in vertebrates and invertebrates disrupts CaV2 channel synaptic localization and synapse function. Here, we describe a previously uncharacterized clade of RIM proteins bearing homologous domain architectures as known RIM homologues, but some notable differences including key amino acids associated with PDZ domain ligand specificity. This novel RIM emerged near the stem lineage of metazoans and underwent extensive losses, but is retained in select animals including the early-diverging placozoan Trichoplax adhaerens, and molluscs. RNA expression and localization studies in Trichoplax and the mollusc snail Lymnaea stagnalis indicate differential regional/tissue type expression, but overlapping expression in single isolated neurons from Lymnaea. Ctenophores, the most early-diverging animals with synapses, are unique among animals with nervous systems in that they lack the canonical RIM, bearing only the newly identified homologue. Through phylogenetic analysis, we find that CaV2 channel D/E-D/E/H-WC-COOH like PDZ ligand motifs were present the common ancestor of cnidarians and bilaterians. We also delineate some deeply conserved C-terminal structures that distinguish CaV1 from CaV2 channels, and CaV1/CaV2 from CaV3 channels.
-
Neuropeptidergic integration of behavior in Trichoplax adhaerens, an animal without synapses.
The Journal of experimental biology, 2017Co-Authors: Adriano Senatore, Thomas S. Reese, Carolyn L SmithAbstract:Trichoplax adhaerens is a flat, millimeter-sized marine animal that adheres to surfaces and grazes on algae. Trichoplax displays a repertoire of different feeding behaviors despite the apparent absence of a true nervous system with electrical or chemical synapses. It glides along surfaces to find food, propelled by beating cilia on cells at its ventral surface, and pauses during feeding by arresting ciliary beating. We found that when endomorphin-like peptides are applied to an animal, ciliary beating is arrested, mimicking natural feeding pauses. Antibodies against these neuropeptides label cells that express the neurosecretory proteins and voltage-gated calcium channels implicated in regulated secretion. These cells are embedded in the ventral epithelium, where they comprise only 4% of the total, and are concentrated around the edge of the animal. Each bears a cilium likely to be chemosensory and used to detect algae. Trichoplax pausing during feeding or spontaneously in the absence of food often induce their neighbors to pause as well, even neighbors not in direct contact. Pausing behavior propagates from animal to animal across distances much greater than the signal that diffuses from just one animal, so we presume that the peptides secreted from one animal elicit secretion from nearby animals. Signal amplification by peptide-induced peptide secretion explains how a small number of sensory secretory cells lacking processes and synapses can evoke a wave of peptide secretion across the entire animal to globally arrest ciliary beating and allow pausing during feeding.
Jürg Spring - One of the best experts on this subject based on the ideXlab platform.
-
Expression pattern of the homeobox gene Not in the basal metazoan Trichoplax adhaerens
Gene expression patterns : GEP, 2004Co-Authors: Cosimo Martinelli, Jürg SpringAbstract:The homeobox gene Not is highly conserved in Xenopus, chicken and zebrafish with an apparent role in notochord formation, which inspired the name of this distinct subfamily. Interestingly, Not genes are also well conserved in animals without notochord such as sea urchins, Drosophila or even Hydra, but appear to be highly derived in mammals. A search for homeobox genes in the placozoan Trichoplax adhaerens, one of the simplest organisms available today, revealed only two homeobox genes: a Not homologue and the previously described gene Trox-2, which is most similar to the Gsx subfamily of the Hox/ParaHox cluster genes. Not has a unique expression profile in Trichoplax. It is highly expressed in folds of intact animals and in the wounds of regenerating animals. The dynamic expression pattern of Trichoplax Not is discussed in comparison with the invariable expression pattern of Trox-2 and the putative secreted protein Secp1. The high sequence conservation of Not from Trichoplax to lower vertebrates, but not to mammals, represents a rare example of an apparent gene decay in the lineage leading to humans.
-
Distinct expression patterns of the two T-box homologues Brachyury and Tbx2/3 in the placozoan Trichoplax adhaerens
Development Genes and Evolution, 2003Co-Authors: Cosimo Martinelli, Jürg SpringAbstract:Trichoplax adhaerens is the only species known from the phylum Placozoa with one of the simplest metazoan body plans. In the small disc-like organism an upper and a lower epithelium can be distinguished with a less compact third cell layer in between. When Trichoplax was first described in 1883, the relation of these three cell layers with ectoderm, endoderm and mesoderm of higher animals was discussed. Still, little is known about embryonic development of Trichoplax , however, genes thought to be specific for mesoderm in bilaterian animals turned out to be already present in non-bilaterians. Searching for a Brachyury homologue, two members of the T-box gene family were isolated from Trichoplax , Brachyury and a Tbx2/3 homologue. The T-box genes encode a transcription factor family characterized by the DNA-binding T-box domain. T-box genes have been found in all metazoans so far investigated, but in contrast to other transcription factors such as the homeobox family, T-box genes are not present in plants or fungi. The distinct expression patterns of two T-box genes in Trichoplax point to non-redundant functions already present at the beginning of animal evolution. Since the expression patterns derived by in situ hybridization do not overlap with anatomical structures, it can be concluded that this simple animal has more than the four cell types described in the literature. This hidden complexity and the unresolved position in relation to Porifera, Cnidaria, Ctenophora and Bilateria highlight the necessity of the inclusion of Trichoplax in studies of comparative evolutionary and developmental biology.
-
distinct expression patterns of the two t box homologues brachyury and tbx2 3 in the placozoan Trichoplax adhaerens
Development Genes and Evolution, 2003Co-Authors: Cosimo Martinelli, Jürg SpringAbstract:Trichoplax adhaerens is the only species known from the phylum Placozoa with one of the simplest metazoan body plans. In the small disc-like organism an upper and a lower epithelium can be distinguished with a less compact third cell layer in between. When Trichoplax was first described in 1883, the relation of these three cell layers with ectoderm, endoderm and mesoderm of higher animals was discussed. Still, little is known about embryonic development of Trichoplax, however, genes thought to be specific for mesoderm in bilaterian animals turned out to be already present in non-bilaterians. Searching for a Brachyury homologue, two members of the T-box gene family were isolated from Trichoplax, Brachyury and a Tbx2/3 homologue. The T-box genes encode a transcription factor family characterized by the DNA-binding T-box domain. T-box genes have been found in all metazoans so far investigated, but in contrast to other transcription factors such as the homeobox family, T-box genes are not present in plants or fungi. The distinct expression patterns of two T-box genes in Trichoplax point to non-redundant functions already present at the beginning of animal evolution. Since the expression patterns derived by in situ hybridization do not overlap with anatomical structures, it can be concluded that this simple animal has more than the four cell types described in the literature. This hidden complexity and the unresolved position in relation to Porifera, Cnidaria, Ctenophora and Bilateria highlight the necessity of the inclusion of Trichoplax in studies of comparative evolutionary and developmental biology.
