Biology subjects

Kenny, N. J.

Publications and source records attributed to Kenny, N. J..

15 recordsLinked to original sources

bioRxiv2025

The genome of the charismatic sea star Linckia laevigata

Linckia laevigata is a tropical sea star commonly found throughout the Indian and Pacific Oceans, and is one of the top ten-most collected invertebrates, often encountered in the aquarium trade. It has been the subject of investigations into population structure, biodiversity and ecology, particularly regarding gene flow among populations throughout its range, the status of different colour morphs and its relationship with its putative sister species, L. multifora. Here we present and describe a high-quality genome assembly for L. laevigata. Our assembly is 585.97 Mb in length, with a scaffold N50 of 3 Mb. The genome has a typical repeat (36.99%) and GC content (41.33%), when compared with other echinoderm datasets. Our genome annotation recovers 16,178 genes, with high (89.4%) recovery of the metazoan BUSCO set. This novel resource will provide a model organism for studying the biogeography of the tropical Indo-West Pacific region, and more specifically facilitate the investigation of a range of sea star traits at the genomic level. SignificanceSea stars remain poorly characterised at a genomic level. Data from the charismatic tropical sea star Linckia laevigata will enable future studies into the biology, population structure and evolution of these ecologically important species.

genetics↗

bioRxiv2024

The Regulatory Logic of Planarian Stem Cell Differentiation

Cell type identity is determined by gene regulatory networks (GRNs), comprising the expression of specific transcription factors (TFs) regulating target genes (TGs) via binding to open chromatin regions (OCRs). The regulatory logic of differentiation includes factors specific to one or multiple cell types, functioning in a combinatorial fashion. Classic approaches of GRN discovery used perturbational data to elucidate TF-TG links, but are laborious and not scalable across the tree of life. Single cell transcriptomics has emerged as a revolutionary approach to study gene expression with cell type resolution, but incorporating perturbational data is challenging. Planarians, with their pluripotent neoblast stem cells continuously giving rise to all cell types, offer an ideal model to attempt this integration. Despite extensive single cell transcriptomic studies, the transcriptional and chromatin regulation at the cell type level remains unexplored. Here, we investigate the regulatory logic of planarian stem cell differentiation by obtaining an organism-level integration of single cell transcriptomics and single cell accessibility data. We identify specific open chromatin profiles for major differentiated cell types and analyse their transcriptomic landscape, revealing distinct gene modules expressed in individual types and combinations of them. Integrated analysis unveils gene networks reflecting known TF interactions in each type and identifies TFs potentially driving differentiation across multiple cell types. To validate our predictions, we combined TF knockdown RNAi experiments with single cell transcriptomics. We focus on hnf4, a TF known to be expressed in gut phagocytes, and confirm its influence on other types, including parenchymal cells. Our results demonstrate high overlap between predicted targets and experimentally-validated differentially-regulated genes. Overall, our study integrates TFs, TGs and OCRs to reveal the regulatory logic of planarian stem cell differentiation, showcasing that the combination of single cell methods and perturbational studies will be key for characterising GRNs widely.

systems biology↗

bioRxiv2024

Independent origins of spicules reconcile the evolutionary history of sponges

Sponges (Porifera) play a critical role in global biogeochemical processes. However, their evolutionary timeline remains unclear hampering our understanding of Neoproterozoic paleoecology. Molecular data suggest a Tonian or Cryogenian origin, while the oldest confirmed sponge fossils, represented by siliceous spicules, date to the Ediacaran. To understand this 150-million-year discrepancy, we compiled a new phylogenomic dataset, revised fossil evidence, derived a new dated sponge phylogeny, and tested whether ancestral sponges were aspiculated or not. We infer the last common sponge ancestor to have been early Ediacaran in age and aspiculated. Siliceous spicules evolved independently at least four times, and calcareous spicules at least two times in crown sponges. We performed a diversification rate analysis showing that siliceous spicules did not drive species radiations. Our study reconciles molecular and fossil evidence, indicating that while sponges emerged in the early Ediacaran, they are largely absent from the Neoproterozoic fossil record because they had not yet evolved spicules. TeaserSponges emerged in the Precambrian, were soft-bodied and did not produce mineralized spicules, which emerged multiple times independently.

evolutionary biology↗

bioRxiv2024

The Hydractinia cell atlas reveals cellular and molecular principles of cnidarian coloniality

Coloniality is a widespread growth form in cnidarians, tunicates, and bryozoans, among others. Despite being modular, composed of multiple zooids and supporting tissues, colonies function as a single physiological unit. A major question in the biology of colonies is the cellular mechanism of generating structurally and functionally distinct colony parts. The cnidarian Hydractinia establishes colonies with different types of zooids (polyps), interconnected by a gastrovascular system that is attached to the substrate and known as stolons. We obtained single cell transcriptomic profiles of [~]200K Hydractinia cells, including isolated stolons and two polyp types. We characterised the major Hydractinia cell types and quantified their abundance across colony parts. Overall, we find that distinct colony parts are characterised primarily by distinct combinations of shared cell types and to a lesser extent by part-specific cell types. Therefore, we propose that both cell type combinations, as well as rarer cell type innovations, have been the main mechanism in the evolution of coloniality in cnidarians. We identified cell type-specific transcription factors (TFs) and gene networks expressed within these cell types. Notably, we discovered a previously unidentified, stolon-specific cell type, which expresses enzymes related to biomineralization and chitin synthesis, reminiscent of molluscan shell matrix proteins that may represent a crucial adaptation to the animals habitat. In summary, the Hydractinia cell atlas elucidates the fundamental cellular and molecular mechanisms underlying coloniality.

systems biology↗

bioRxiv2022

A single amino acid change drives left- right asymmetry in Bilateria

Asymmetries are essential for proper organization and function of organ systems. Genetic studies in deuterostomes have shown signaling through the Nodal/Smad2 pathway plays a key, conserved role in the establishment of body asymmetries. While Nodal signaling is required for the establishment of left-right asymmetry (LRA) across bilaterian species, little is known about the regulation of Nodal signaling in spiralians. Here, we identified orthologs of the egf-cfc gene, a master regulator of the Nodal pathway in vertebrates, in several invertebrate species, the first evidence of its presence in non-deuterostomes. Our functional experiments indicate that despite being present, egf-cfc does not play a role in the establishment LRA in gastropods. However, experiments in zebrafish suggest that a single amino acid mutation in the egf-cfc gene in the deuterostome common ancestor was the necessary step in inducing a gain-of-function in LRA regulation. This study shows that that the egf-cfc gene likely appeared in the bilaterian stem lineage, before being adopted as a master mechanism to regulate the Nodal pathway and the establishment of LRA in deuterostomes.

developmental biology↗

bioRxiv2022

An atlas of spider development at single-cell resolution provides new insights into arthropod embryogenesis

Spiders are a diverse order of chelicerates that diverged from other arthropods over 500 million years ago. Research on spider embryogenesis, particular studies using the common house spider Parasteatoda tepidariorum, has made important contributions to understanding the evolution of animal development, including axis formation, segmentation, and patterning. However, we lack knowledge about the cells that build spider embryos, their gene expression profiles and fate. Single-cell transcriptomic analyses have been revolutionary in describing these complex landscapes of cellular genetics in a range of animals. Therefore, we carried out single-cell RNA sequencing of P. tepidariorum embryos at stages 7, 8 and 9, which encompass the establishment and patterning of the body plan, and initial differentiation of many tissues and organs. We identified 20 cell clusters, from 18.5k cells, which were marked by many developmental toolkit genes, as well as a plethora of genes not previously investigated. There were differences in the cell cycle transcriptional signatures, suggestive of different proliferation dynamics, which related to distinctions between endodermal and some mesodermal clusters, compared with ectodermal clusters. We found many Hox genes were markers of cell clusters, and Hox gene ohnologs often were present in different clusters. This provided additional evidence of sub- and/or neo-functionalisation of these important developmental genes after the whole genome duplication in the arachnopulmonate ancestor (spiders, scorpions, and allies). We also examined the spatial expression of marker genes for each cluster to generate a comprehensive cell atlas of these embryonic stages. This revealed new insights into the cellular basis and genetic regulation of head patterning, hematopoiesis, limb development, gut development, and posterior segmentation. This atlas will serve as a platform for future analysis of spider cell specification and fate, and studying the evolution of these processes among animals at cellular resolution.

developmental biology↗

bioRxiv2020

Striking parallels between dorsoventral patterning in Drosophila and Gryllus reveal a complex evolutionary history behind a model gene regulatory network

Dorsoventral pattering relies on Toll and BMP signalling in all insects studied so far, with variations in the relative contributions of both pathways. Drosophila and the beetle Tribolium share extensive dependence on Toll, while representatives of more distantly related lineages like the wasp Nasonia and bug Oncopeltus rely more strongly on BMP signalling. Here, we show that in the cricket Gryllus bimaculatus, an evolutionarily distant outgroup, Toll has, like in Drosophila, a direct patterning role for the ventral half of the embryo. In addition Toll polarizes BMP signalling, although this does not involve the conserved BMP inhibitor Sog/Chordin. Finally, Toll activation relies on ovarian patterning mechanisms with striking similarity to Drosophila. Our data suggest two surprising hypotheses: 1) that Tolls patterning function in Gryllus and Drosophila is the result of convergent evolution or 2) a Drosophila-like system arose early in insect evolution, and was extensively altered in multiple independent lineages.

evolutionary biology↗

bioRxiv2020

Single individual structural variant detection uncovers widespread hemizygosity in molluscs

The advent of complete genomic sequencing has opened a window into genomic phenomena obscured by fragmented assemblies. A good example of these is the existence of hemizygous regions of autosomal chromosomes, which can result in marked differences in gene content between individuals within species. While these hemizygous regions, and presence/absence variation of genes that can result, are well known in plants, firm evidence has only recently emerged for their existence in metazoans. Here we use recently published, complete genomes from wild-caught molluscs to investigate the prevalence of hemizygosity and pan-genomes across a well-known and ecologically important clade. We show that hemizygous regions are widespread in mollusc genomes, not clustered in individual chromosomes, and often contain genes linked to transposition, DNA repair and stress response. With targeted investigations of HSP70-12 and C1qDC, we also show how individual gene families are distributed within pan-genomes. This work suggests that pan-genomes are widespread across the conchiferan Mollusca, and represent useful tools for genomic evolution, allowing the maintenance of additional genetic diversity within the population. As genomic sequencing and re-sequencing becomes more routine, the prevalence of hemizygosity, and its impact on selection and adaptation, are key targets for research across the tree of life.

genomics↗

bioRxiv2020

ACME dissociation: a versatile cell fixation-dissociation method for single-cell transcriptomics

Single-cell sequencing technologies are revolutionizing biology, but are limited by the need to dissociate fresh samples that can only be fixed at later stages. We present ACME (ACetic-MEthanol) dissociation, a cell dissociation approach that fixes cells as they are being dissociated. ACME-dissociated cells have high RNA integrity, can be cryopreserved multiple times, can be sorted by Fluorescence-Activated Cell Sorting (FACS) and are permeable, enabling combinatorial single-cell transcriptomic approaches. As a proof of principle, we have performed SPLiT-seq with ACME cells to obtain around ∼34K single cell transcriptomes from two planarian species and identified all previously described cell types in similar proportions. ACME is based on affordable reagents, can be done in most laboratories and even in the field, and thus will accelerate our knowledge of cell types across the tree of life.Competing Interest StatementThe authors have declared no competing interest.View Full Text

systems biology↗

bioRxiv2020

The genomic basis of animal origins: a chromosomal perspective from the sponge Ephydatia muelleri

The genomes of non-bilaterian metazoans are key to understanding the molecular basis of early animal evolution. However, a full comprehension of how animal-specific traits such as nervous systems arose is hindered by the scarcity and fragmented nature of genomes from key taxa, such as Porifera. Ephydatia muelleri is a freshwater sponge found across the northern hemisphere. Here we present its 326 Mb genome, assembled to high contiguity (N50: 9.88 Mb) with 23 chromosomes on 24 scaffolds. Our analyses reveal a metazoan-typical genome architecture, with highly shared synteny across Metazoa, and suggest that adaptation to the extreme temperatures and conditions found in freshwater often involves gene duplication. The pancontinental distribution and ready laboratory culture of E. muelleri make this a highly practical model system, which with RNAseq, DNA methylation and bacterial amplicon data spanning its development and range allows exploration of genomic changes both within sponges and in early animal evolution.

evolutionary biology↗

bioRxiv2020

The Gene-Rich Genome of the Scallop Pecten maximus

BackgroundThe King Scallop, Pecten maximus, is distributed in shallow waters along the Atlantic coast of Europe. It forms the basis of a valuable commercial fishery and its ubiquity means that it plays a key role in coastal ecosystems and food webs. Like other filter feeding bivalves it can accumulate potent phytotoxins, to which it has evolved some immunity. The molecular origins of this immunity are of interest to evolutionary biologists, pharmaceutical companies and fisheries management. FindingsHere we report the genome sequencing of this species, conducted as part of the Wellcome Sanger 25 Genomes Project. This genome was assembled from PacBio reads and scaffolded with 10x Chromium and Hi-C data, and its 3,983 scaffolds have an N50 of 44.8 Mb (longest scaffold 60.1 Mb), with 92% of the assembly sequence contained in 19 scaffolds, corresponding to the 19 chromosomes found in this species. The total assembly spans 918.3 Mb, and is the best-scaffolded marine bivalve genome published to date, exhibiting 95.5% recovery of the metazoan BUSCO set. Gene annotation resulted in 67,741 gene models. Analysis of gene content revealed large numbers of gene duplicates, as previously seen in bivalves, with little gene loss, in comparison with the sequenced genomes of other marine bivalve species. ConclusionsThe genome assembly of Pecten maximus and its annotated gene set provide a high-quality platform for a wide range of investigations, including studies on such disparate topics as shell biomineralization, pigmentation, vision and resistance to algal toxins. As a result of our findings we highlight the sodium channel gene Nav1, known as a gene conferring resistance to saxitoxin and tetrodotoxin, as a candidate for further studies investigating immunity to domoic acid.

genomics↗

bioRxiv2018

Freshwater Adaptation at the Molecular Scale in the Unique Sponges of Lake Baikal

Freshwater sponges (Spongillida) are a unique lineage of demosponges that secondarily colonized lakes and rivers and are now found ubiquitously in these ecosystems. They developed specific adaptations to freshwater systems, including the ability to survive extreme thermal ranges, long-lasting dessication, anoxia, and resistance to a variety of pollutants. While spongillids have colonized all freshwater systems, the family Lubomirskiidae is endemic to Lake Baikal, and plays a range of key roles in this ecosystem. Our work compares the genomic content and microbiome of individuals of three species of the Lubomirskiidae, providing hypotheses for how molecular evolution has allowed them to adapt to their unique environments. We have sequenced deep (>92% of the metazoan Benchmarking Universal Single-Copy Orthologs (BUSCO) set) transcriptomes from three species of Lubomirskiidae and a draft genome resource for Lubomirskia baikalensis. We note Baikal sponges contain unicellular algal and bacterial symbionts, as well as the dinoflagellate Gyrodinium. We investigated molecular evolution, gene duplication and novelty in freshwater sponges compared to marine lineages. Sixty one orthogroups have consilient evidence of positive selection. Transporters (e.g. zinc transporter-2), transcription factors (aristaless-related homeobox) and structural proteins (for example actin-3), alongside other genes, are under strong evolutionary pressure in freshwater, with duplication driving novelty across the Spongillida, but especially in the Lubomirskiidae. This addition to knowledge of freshwater sponge genetics provides a range of tools for understanding the molecular biology and, in the future, the ecology (for example, colonization and migration patterns) of these key species.

zoology↗

bioRxiv2018

Warm Temperatures, Cool Sponges: The Effect of Increased Temperatures on the Antarctic Sponge Isodictya sp.

Although the cellular and molecular responses to exposure to relatively high temperatures (acute thermal stress or heat shock) have been studied previously, only sparse empirical evidence of how it affects cold-water species is available. As climate change becomes more pronounced in areas such as the Western Antarctic Peninsula, it has become crucial to understand the capacity of these species to respond to thermal stress. Here we use the Antarctic sponge Isodictya sp. to investigate how sessile organisms (particularly Porifera) can adjust to acute short-term heat stress, by exposing this species to 3 and 5 {degrees}C for 4 hours, corresponding to predicted temperatures under high-end 2080 IPCC-SRES scenarios. Assembling a de novo reference transcriptome (90,188 contigs, >93.7% metazoan BUSCO genes) we have begun to discern the molecular componentry employed by Isodictya to adjust to environmental insult. Our initial analyses suggest that TGF-{beta}, ubiquitin and hedgehog cascades are involved, alongside other genes. However, the degree and type of response changed little from 3 to 5 {degrees}C, suggesting that even moderate rises in temperature could cause stress at the limits of this organisms capacity. Given the importance of sponges to Antarctic ecosystems, our findings are vital for discerning the consequences of increases in Antarctic ocean temperature on these and other species.

genomics↗

bioRxiv2017

Ancestrally Shared Regenerative Mechanisms Across the Metazoa: A Transcriptomic Case Study in the Demosponge Halisarca caerulea

Regeneration is an essential process for all multicellular organisms, allowing them to recover effectively from internal and external injury. This process has been studied extensively in a medical context in vertebrates, with pathways often investigated mechanistically, both to derive increased understanding and as potential drug targets for therapy. Several species from other parts of the metazoan tree of life, noted for their regenerative prowess, have previously been targeted for study. This allows us to understand their regenerative mechanisms and see how they could be adapted for use in medicine. Species in clades such as Hydra, planarians and echinoderms can regenerate large portions of their body, the former two clades being able to completely regenerate from even a small portion of their somatic tissue. Less well-documented for their regenerative abilities are sponges. This is surprising, as they are both one of the earliest-branching extant metazoan phyla on Earth, and are rapidly able to respond to injury. Their sessile lifestyle, lack of an external protective layer, inability to respond to predation and filter-feeding strategy all mean that regeneration is often required. In particular the demosponge genus Halisarca has been noted for its fast cell turnover and ability to quickly adjust its cell kinetic properties to repair damage through regeneration. However, while the rate and structure of regeneration in sponges has begun to be investigated, the molecular mechanisms behind this ability are yet to be catalogued.\n\nHere we describe the assembly of a reference transcriptome for Halisarca caerulea, along with additional transcriptomes noting response to injury before, shortly following (2 hrs post-), and 12 hrs after trauma. RNAseq reads were assembled using Trinity, annotated, and samples compared, to allow initial insight into the transcriptomic basis of sponge regenerative processes. These resources are deep, with our reference assembly containing more than 92.6% of the BUSCO Metazoa set of genes, and well-assembled (N50s of 836, 957, 1,688 and 2,032 for untreated, 2h, 12h and reference transcriptomes respectively), and therefore represent excellent initial resources as a bedrock for future study. The generation of transcriptomic resources from sponges before and following deliberate damage has allowed us to study particular pathways within this species responsible for repairing damage. We note particularly the involvement of the Wnt cascades in this process in this species, and detail the contents of this cascade, along with cell cycle, extracellular matrix and apoptosis-linked genes in this work.\n\nThis resource represents an excellent starting point for the continued development of this knowledge, given H. caeruleas ability to regenerate and position as an outgroup for comparing the process of regeneration across metazoan lineages. With this resource in place, we can begin to infer the regenerative capacity of the common ancestor of all extant animal life, and unravel the elements of regeneration in an often-overlooked clade.

genomics↗

bioRxiv2017

A novel role for Ets4 in axis specification and cell migration in the spider Parasteatoda tepidariorum

Organizers play important roles during the embryonic development of many animals. The most famous example is the Spemann organizer that sets up embryonic axes in amphibian embryos.\n\nIn spiders, a group of BMP secreting mesenchymal cells (the cumulus) functions as an organizer of the dorsoventral axis. Similar to experiments performed with the Spemann organizer, transplantation of the cumulus is able to induce a secondary axis in spiders.\n\nDespite the importance of this structure, it is unknown which factors are needed to activate cumulus specific gene expression.\n\nTo address this question, we performed a transcriptomic analysis of early embryonic development in the spider Parasteatoda tepidariorum. Through this work, we found that the transcription factor Pt-Ets4 is needed for cumulus integrity, dorsoventral patterning and for the activation of Pt-hunchback and Pt-twist expression. Furthermore, ectopic expression of Pt-Ets4 is sufficient to induce cell delamination and migration by inducing a mesoderm-like cell fate.

developmental biology↗