Biology subjects

Technau, U.

Publications and source records attributed to Technau, U..

15 recordsLinked to original sources

bioRxiv2026

From promiscuity to specialization: The origin of cholinergic and monoaminergic signaling is pre-bilaterian

The emergence of chemical neurotransmission was key to the evolution of nervous systems, yet when the different transmitter systems arose remains unclear. Biogenic amines (here, acetylcholine and the monoamines) have been reported in non-bilaterian animals and even outside Metazoa, but their physiological role has only recently begun to be resolved, and phylogenetic surveys of the bilaterian machinery have restricted dedicated monoaminergic signaling to Bilateria. Combining targeted metabolomics, molecular phylogenies, structural modeling and binding-affinity prediction, single-cell expression analysis and immunochemistry, we show that cholinergic and monoaminergic signaling predate Bilateria. We detect acetylcholine, dopamine, histamine, adrenaline, tyramine, 2-phenylethylamine and tryptamine in a sponge and two cnidarians, and identify broad-specificity enzymes and transporters able to produce and load them. These genes are co-expressed in both neuronal and non-neuronal cell types, indicating that amine signaling was never confined to the nervous system. Two Hydra vulgaris muscarinic receptor orthologs retain a fully conserved orthosteric site and are predicted to bind acetylcholine as strongly as their bilaterian counterparts, and muscle-type nicotinic receptor subunits are co-expressed with Rapsyn-related genes in cnidarian muscle cells, placing cholinergic neuromuscular signaling in the cnidarian-bilaterian ancestor. Specialization came later in Bilateria, where gene duplications produced substrate-specific enzymes (ChAT, TH, TPH), dedicated vesicular transporters (VAChT, VMAT) and ligand-selective receptors. Biogenic amine signaling is thus not a bilaterian innovation but an ancient mode of cellular communication that evolved from generalist to specialist machinery.

evolutionary biology↗

bioRxiv2025

Notch coordinates self-organization of germ layers and axial polarity in cnidarian gastruloids

Dissociation and reaggregation experiments in several animal systems have revealed the stunning capacity of self-organization. Reaggregated early gastrula cells (here called gastruloids) of the sea anemone Nematostella vectensis are able to regenerate with only little delay whole organisms that are virtually indistinguishable from normal developing polyps. However, the molecular control underlying the restoration of body axis and germ layers remains largely unknown. To address this, we established a standardized protocol, which reproducibly generates gastruloids developing into polys with a single body axis. Here, we show that committed mesodermal and endodermal cells are sorted out to the surface of the aggregate, where mesodermal cells form clusters of about 30 cells. At a critical time point, one mesodermal cluster immigrates, along with peripherally attached endodermal cells. Thereby, the inner germ layer and the oral-aboral axis is established in one and the same process. Functional studies demonstrated that this polarization of the endodermal cells requires a feedback loop of Notch and Wnt signaling. The dissociation of the early embryo disrupts Notch signaling in the endodermal cells, which leads to transient adoption of an endomesodermal profile, marked by the expression of the mesodermal cadherin1 until the boundaries between the germ layer identities are re-established. Our results highlight distinct morphogenetic behaviors of mesodermal and endodermal cells and the hitherto unknown role of Notch signaling in germ layer boundary formation in self-organizing gastruloids. Conservation of Notch-mediated boundary formation between endoderm and mesoderm mirrors bilaterian mechanisms, demonstrating how adoption of ancestral regulatory networks governing morphogenesis likely enabled the diversification of metazoan body plans.

developmental biology↗

bioRxiv2025

Loss of Twist impairs tentacle development and induces epithelial neoplasia in the sea anemone Nematostella vectensis

The basic helix-loop helix transcription factor Twist plays diverse roles in mesodermal development across bilaterians, but its function in cnidarians remains unclear. Here, we investigate the role of Twist in tentacle morphogenesis and tissue homeostasis in the sea anemone Nematostella vectensis. Using a CRISPR/Cas9 generated knockout, we show that twist mutants exhibit impaired secondary tentacle formation, reduced proliferation in budding tentacles. Cross-sections reveal that mutants also lack micronemes, which are incomplete mesenteries that demarcate tentacle boundaries-suggesting defects in spatial patterning. We demonstrate that twist expression is regulated by Wnt, BMP, and Notch signalling but is independent of MAPK and Hedgehog pathways. Loss of Twist disrupts expression of mesodermal transcription factors paraxis and tbx15 and perturbs the TOR-FGF signalling feedback loop necessary for normal tentacle growth. In addition to the impaired tentacle formation phenotype, juvenile or adult mutants develop epithelial neoplasms at the level of the pharynx, with tentacle-like molecular and morphological profiles, indicating a role for Twist in maintaining tissue homeostasis at the oral pole. Together, our findings reveal that Twist integrates major signalling pathways to regulate secondary tentacle patterning and maintain spatial tissue organisation in the diploblastic Nematostella vectensis.

developmental biology↗

bioRxiv2025

Phagocytosis repurposed: infection strategies in a globalmarine diatom-parasite interaction

Microbial host-parasite interactions shape global biogeochemical cycles, yet their cellular and evolutionary mechanisms remain poorly understood. Here, we developed a novel model pathosystem to explore the interaction between the globally distributed eukaryotic microparasite, Pirsonia, and its host, the bloom-forming diatom, Coscinodiscus. Culture conditions recapitulated Pirsonias rapid life cycle in vitro and live-cell imaging enabled quantitative assessments of infection dynamics and host mortality. To investigate the genetic basis of this interaction, we assembled the Pirsonia genome and identified unique genetic innovations relative to their oomycete relatives. Time-resolved dual RNA-Seq enabled tracking of parasite gene expression through the infection cycle and revealed an upregulation of an expanded multi-gene family of integrin-like proteins in Pirsonia zoospores, analogous to the variable surface proteins in other parasitic lineages. Genes upregulated during infection were associated with cytoskeletal dynamics and drug inhibition assays confirmed that actin is required for host infection, consistent with the presence of parasitic pseudopodia on infected hosts. The dependence on both actin-based phagocytic mechanisms and parasitic-like surface proteins highlights Pirsonias intermediate state between predator and parasite, providing new insights into the evolution of parasite strategies and the complex cellular interactions controlling parasitic shunts in marine trophic networks.

evolutionary biology↗

bioRxiv2025

Functional analysis of ligand-gated chloride channels in a cnidarian sheds light on the evolution of inhibitory signalling

{psi}-aminobutyric acid (GABA) is the predominant inhibitory transmitter in the vertebrate nervous system. Fast inhibitory signalling is mediated by type A GABA receptors (GABAARs), which form pentameric ligand-gated ion channels. While GABA is also present in plants and prokaryotes, it is unknown when it was first used for fast neuronal transmission. Cnidaria represent a sister group to all Bilateria and possess a variety of putative GABAARs, none of which has been functionally characterized. In this study, we surveyed putative inhibitory ion channel receptors from the model cnidarians Nematostella and Hydra. Phylogenetic analysis revealed a surprising complexity of these receptors. The majority formed a cnidarian-specific radiation with some receptors forming a basal clade. We functionally analyzed seven putative Nematostella GABAARs of this radiation and found that none was activated by GABA or glycine, whereas three were activated by glutamate. Using site-directed mutagenesis, we identified a lysine residue in the canonical ligand-binding pocket that is important for activation by glutamate. Our results identified a group of inhibitory ion channel receptors in Cnidaria that uses glutamate as a ligand. Moreover, they suggest that inhibitory ion channel receptors in Cnidaria massively diversified, which may have been instrumental in the evolution of complex behaviors and sensory processing by the cnidarian nervous system. This work lays the foundation for understanding the diversity and evolution of inhibitory receptors in Cnidaria and the evolution of inhibitory signalling in animal nervous systems.

neuroscience↗

bioRxiv2024

Notch, beta-catenin and MAPK signaling segregate endoderm and mesoderm in the diploblast Nematostella vectensis

Cnidaria are typically considered diploblastic (i.e. consisting of two germ layers) in contrast to their triploblastic sister clade, the Bilateria. However, a recent study suggested that sea anemones and other cnidarians have three segregated germ layer identities, corresponding to the bilaterian germ layers1. Here, we investigated, how the three germ layer identities are specified during early development of the sea anemone Nematostella vectensis. First, the mesodermal territory is specified at the animal pole at 6 hours postfertilization, followed by the specification of a ring of endodermal territory between mesoderm and ectoderm. We then assessed the role of {beta}-catenin, MAPK and Notch signaling pathways during mesoderm and endoderm formation. Our results show that the mesoderm is initiated by MAPK signaling and simultaneously restricted to the future oral side by mutually exclusive nuclear {beta}-catenin signaling. The mesodermal cells then express the Delta ligand, while the ectodermal cells express the Notch receptor. Inhibition of Notch signaling as well as ectopic expression of the Notch intracellular domain showed that endodermal tissue identity is induced by Notch signaling at the boundary between mesoderm and ectoderm. We propose a new model that outlines the different steps leading to the segregation of mesoderm and endoderm identities in Nematostella, confirming the presence of 3 distinct germ layer identities in this cnidarian. Notably, the observed crosstalk of MAPK, {beta}-catenin and Notch signaling in the specification of three germ layers in Nematostella is highly reminiscent to early stage gastrulae of sea urchins suggesting that triploblasty may predate the split of cnidarians and bilaterians.

developmental biology↗

bioRxiv2023

Nanos2+ cells give rise to germline and somatic lineages in the sea anemone Nematostella vectensis

In all animals, stem cell populations of varying potency facilitate regeneration and tissue homeostasis. Notably, germline stem cells in both vertebrates and invertebrates express highly conserved RNA-binding proteins, such as nanos, vasa and piwi. Interestingly, in animals, which are capable of whole-body regeneration, such as poriferans, hydrozoans and planarians, these genes are also expressed in somatic multi- and pluripotent stem cells, which led to the proposal that they had an ancestral role in all stem cells. While multi- and pluripotent interstitial stem cells have been identified in hydrozoans, they have not unambiguously been demonstrated in other cnidarian classes. Therefore, it is currently unclear if these stem cell systems share a common evolutionary origin or have been adapted individually in different lineages as homoplasy. We therefore aimed to characterize stem cells expressing conserved stem cell marker genes in the sea anemone Nematostella vectensis, to gain insight of shared traits governing the regulation of this enigmatic cell type. Through single cell transcriptomics, we identify cell populations expressing the germline associated markers piwi1 and nanos2 in the soma and germline. Transgenic reporter genes reveal a lineage giving rise to somatic cells, consistent with a role as a multipotent stem cell population. Cell proliferation studies show that a fraction of nanos2+ reporter cells are cycling and CRISPR/Cas9 mediated gene knockout show that nanos2+ progenitor cells are indispensable for male and female germline maintenance in Nematostella. This suggests nanos and piwi genes have a conserved role in somatic and germline stem cells in cnidarians.

developmental biology↗

bioRxiv2023

A cell-type atlas from a scyphozoan jellyfish Aurelia coerulea (formerly sp.1) provides insights into changes of cell-type diversity in the transition from polyps to medusae

The life cycle of most medusozoan cnidarians is marked by the metagenesis from the asexually reproducing sessile polyp and the sexually reproducing motile medusa. At present it is unknown to what extent this drastic morphological transformation is accompanied by molecular changes in the cell type composition. Here, we provide a single cell transcriptome atlas of the cosmopolitan scyphozoan Aurelia coerulea focusing on changes in individual cell states during the transition from polyp to medusa. Notably, this transition is marked by an increase in cell type diversity, including an expansion of neural subtypes and the appearance of striated muscles. We find that two families of neuronal lineages are specified by homologous transcription factors in the sea anemone Nematostella vectensis and Aurelia coerulea, suggesting an origin in the common ancestor of medusozoans and anthozoans about 500 Myr ago. Our analysis suggests that gene duplications might be drivers for the increase of cellular complexity during the evolution of cnidarian neuroglandular lineages and highlight the close relationship of neurons and muscles. One key medusozoan-specific cell type is the striated muscle in the subumbrella. Evaluating muscle types by fibre anatomy and gene expression validation of their individual molecular profiles made it possible for the first time to investigate transcriptome differences between smooth and striated muscles. Although smooth and striated muscles are phenotypically different, both have a similar regulation of the contractile complex, reminiscent to the regulation of smooth muscles in bilaterians. This is in contrast to bilaterian striated muscles, where the regulation of muscle contraction involves Ca2+ binding troponins and their interaction with Tropomyosin. This suggests that smooth muscle contraction regulation is ancestral and the use of troponins in striated muscles only evolved in bilaterians. TeaserSingle cell transcriptome atlas across the jellyfish life cycle reveals emergence of novel medusa-specific cell types associated with expression of medusa-specific paralogs.

evolutionary biology↗

bioRxiv2023

Large-scale deorphanization of Nematostella vectensis neuropeptide GPCRs supports the independent expansion of bilaterian and cnidarian peptidergic systems

Neuropeptides are ancient signaling molecules in animals but only few peptide receptors are known outside bilaterians. Cnidarians possess a large number of G protein-coupled receptors (GPCRs) - the most common receptors of bilaterian neuropeptides - but most of these remain orphan with no known ligands. We searched for neuropeptides in the sea anemone Nematostella vectensis and created a library of 64 peptides derived from 33 precursors. In a large-scale pharmacological screen with these peptides and 161 N. vectensis GPCRs, we identified 31 receptors specifically activated by one of 14 peptides. Mapping GPCR and neuropeptide expression to single-cell sequencing data revealed how cnidarian tissues are extensively connected by multilayer peptidergic networks. Phylogenetic analysis identified no direct orthology to bilaterian peptidergic systems and supports the independent expansion of neuropeptide signaling in cnidarians from a few ancestral peptide-receptor pairs.

neuroscience↗

bioRxiv2022

Single cell transcriptomics identifies conserved regulators of neurosecretory lineages

Communication in bilaterian nervous systems is mediated by electrical and secreted signals, however, the evolutionary origin and relation of neurons to other secretory cell types has not been elucidated. Here we use developmental single cell RNA-sequencing in the cnidarian Nematostella vectensis, representing an early evolutionary lineage with a simple nervous system. Validated by transgenics, we demonstrate that neurons, stinging cells, and gland cells arise from a common multipotent progenitor population. We identify the conserved transcription factor gene SoxC as a key upstream regulator of all neurosecretory lineages and demonstrate that SoxC knockdown eliminates both neuronal and secretory cell types. While in vertebrates and many other bilaterians neurogenesis is largely restricted to early developmental stages, we show that in the sea anemone differentiation of neurosecretory cells is maintained throughout all life stages, and follows the same molecular trajectories from embryo to adulthood, ensuring lifelong homeostasis of neurosecretory cell lineages.

developmental biology↗

bioRxiv2020

Sea anemone genomes reveal ancestral metazoan chromosomal macrosynteny

Draft genome sequences of non-bilaterian species have provided important insights into the evolution of the metazoan gene repertoire. However, there is little information about the evolution of gene clusters, genome architectures and karyotypes during animal evolution. In this regard, slowly evolving anthozoan Cnidaria, the sister group of Bilateria, are particularly informative. Here we report chromosome-level genome assemblies of two related cnidarians, the sea anemones Nematostella vectensis and Scolanthus callimorphus. We find a robust set of 15 chromosomes with a clear one-to-one correspondence between the two species. Both sea anemone genomes show remarkable chromosomal conservation with other cnidarians, several bilaterians and the sponge Ephydatia muelleri, allowing us to reconstruct ancestral cnidarian and metazoan chromosomal blocks, consisting of at least 19 and 16 ancestral linkage groups, respectively. We show that, in contrast to Bilateria, the Hox and NK clusters of investigated cnidarians are largely disintegrated, despite the presence of staggered hox/gbx expression in Nematostella. This loss of microsynteny conservation may be facilitated by shorter distances between cis-regulatory sequences and their cognate transcriptional start sites. In line with that, we find no clear evidence for topologically associated domains, suggesting fundamental differences in long-range gene regulation compared to vertebrates. These data suggest that large sets of ancestral metazoan genes have been retained in ancestral linkage groups of some extant lineages, yet, higher order gene regulation with associated 3D architecture may have evolved only after the cnidarian-bilaterian split.

genomics↗

bioRxiv2020

β-catenin dependent axial patterning in Cnidaria and Bilateria uses similar regulatory logic

In animals, body axis patterning is based on the concentration-dependent interpretation of graded morphogen signals, which enables correct positioning of the anatomical structures. The most ancient axis patterning system acting across animal phyla relies on {beta}-catenin signaling, which directs gastrulation, and patterns the main body axis. However, within Bilateria, the patterning logic varies significantly between protostomes and deuterostomes. To deduce the ancestral principles of {beta}-catenin dependent axial patterning, we investigated the oral-aboral axis patterning in the sea anemone Nematostella - a member of the bilaterian sister group Cnidaria. Here we elucidate the regulatory logic by which more orally expressed {beta}-catenin targets repress more aborally expressed {beta}- catenin targets, and progressively restrict the initially global, maternally provided aboral identity. Similar regulatory logic of {beta}-catenin-dependent patterning in Nematostella and deuterostomes suggests a common evolutionary origin of these processes.

developmental biology↗

bioRxiv2020

Muscle cell type diversification driven by extensive gene duplications

The evolutionary mechanisms underlying the emergence of new cell types are still unclear. Here, we address the origin and diversification of muscle cells in the diploblastic sea anemone Nematostella vectensis. We discern two fast and two slow-contracting muscle cell populations in Nematostella differing by extensive sets of paralogous genes. The regulatory gene set of the slow cnidarian muscles and the bilaterian cardiac muscle are remarkably similar. By contrast, the two fast muscles differ substantially from each other, while driving the same set of paralogous structural protein genes. Our data suggest that extensive gene duplications and co-option of individual effector modules may have played an important role in cell type diversification during metazoan evolution. One Sentence SummaryThe study of the simple sea anemone suggests a molecular mechanism for cell type evolution and morphological complexity.

developmental biology↗

bioRxiv2018

Cadherin switch marks germ layer formation in the diploblastic sea anemone Nematostella vectensis

Morphogenesis is a shape-building process during development of multicellular organisms. During this process the establishment and modulation of cell-cell contacts play an important role. Cadherins, the major cell adhesion molecules, form adherens junctions connecting ephithelial cells. Numerous studies in Bilateria have shown that cadherins are associated with the regulation of cell differentiation, cell shape changes, cell migration and tissue morphogenesis. To date, the role of Cadherins in non-bilaterians is unknown. Here, we study the expression and the function of two paralogous classical cadherins, cadherin1 and cadherin3, in the diploblastic animal, the sea anemone Nematostella vectensis. We show that a cadherin switch is accompanying the formation of germ layers. Using specific antibodies, we show that both cadherins are localized to adherens junctions at apical and basal positions in ectoderm and endoderm. During gastrulation, partial EMT of endodermal cells is marked by a step-wise downregulation of cadherin3 and upregulation of cadherin1. Knockdown experiments show that both cadherins are required for maintenance of tissue integrity and tissue morphogenesis. This demonstrates that cnidarians convergently use cadherins to differentially control morphogenetic events during development.

developmental biology↗

bioRxiv2018

The genome of the jellyfish Clytia hemisphaerica and the evolution of the cnidarian life-cycle

Jellyfish (medusae) are a distinctive life-cycle stage of medusozoan cnidarians. They are major marine predators, with integrated neurosensory, muscular and organ systems. The genetic foundations of this complex form are largely unknown. We report the draft genome of the hydrozoan jellyfish Clytia hemisphaerica and use multiple transcriptomes to determine gene use across life-cycle stages. Medusa, planula larva and polyp are each characterised by distinct transcriptome signatures reflecting abrupt life cycle transitions, and all deploy a mixture of phylogenetically old and new genes. Medusa specific transcription factors, including many with bilaterian orthologs, associate with diverse neurosensory structures. Compared to Clytia, the polyp-only hydrozoan Hydra has lost many of the medusa-expressed transcription factors, despite similar overall rates of gene content and sequence evolution. Absence of expression and gene loss among Clytia orthologs of genes patterning the anthozoan aboral pole, secondary axis and endomesoderm support simplification of planulae and polyps in Hydrozoa, including loss of bilateral symmetry. Consequently, although the polyp and planula are generally considered the ancestral cnidarian forms, in Clytia the medusa maximally deploys ancestral cnidarian-bilaterian transcription factor gene complexity.

evolutionary biology↗