Highly conserved and extremely evolvable: BMP signalling in secondary axis patterning of Cnidaria and Bilateria.

Bilateria encompass the vast majority of the animal phyla. As the name states, they are bilaterally symmetric, that is with a morphologically clear main body axis connecting their anterior and posterior ends, a second axis running between their dorsal and ventral surfaces, and with a left side being roughly a mirror image of their right side. Bone morphogenetic protein (BMP) signalling has widely conserved functions in the formation and patterning of the second, dorso-ventral (DV) body axis, albeit to different extents in different bilaterian species. Whilst initial findings in the fruit fly Drosophila and the frog Xenopus highlighted similarities amongst these evolutionarily very distant species, more recent analyses featuring other models revealed considerable diversity in the mechanisms underlying dorsoventral patterning. In fact, as phylogenetic sampling becomes broader, we find that this axis patterning system is so evolvable that even its core components can be deployed differently or lost in different model organisms. In this review, we will try to highlight the diversity of ways by which BMP signalling controls bilaterality in different animals, some of which do not belong to Bilateria. Future research combining functional analyses and modelling is bound to give us some understanding as to where the limits to the extent of the evolvability of BMP-dependent axial patterning may lie.

Diurnal and circadian regulation of opsin-like transcripts in the eyeless cnidarian Hydra.

Opsins play a key role in the ability to sense light both in image-forming vision and in non-visual photoreception (NVP). These modalities, in most animal phyla, share the photoreceptor protein: an opsin-based protein binding a light-sensitive chromophore by a lysine (Lys) residue. So far, visual and non-visual opsins have been discovered throughout the Metazoa phyla, including the photoresponsive Hydra, an eyeless cnidarian considered the evolutionary sister species to bilaterians. To verify whether light influences and modulates opsin gene expression in Hydra, we utilized four expression sequence tags, similar to two classic opsins (SW rhodopsin and SW blue-sensitive opsin) and two non-visual opsins (melanopsin and peropsin), in investigating the expression patterns during both diurnal and circadian time, by means of a quantitative RT-PCR. The expression levels of all four genes fluctuated along the light hours of diurnal cycle with respect to the darkness one and, in constant dark condition of the circadian cycle, they increased. The monophasic behavior in the L12:D12 cycle turned into a triphasic expression profile during the continuous darkness condition. Consequently, while the diurnal opsin-like expression revealed a close dependence on light hours, the highest transcript levels were found in darkness, leading us to novel hypothesis that in Hydra, an "internal" biological rhythm autonomously supplies the opsins expression during the circadian time. In conclusion, in Hydra, both diurnal and circadian rhythms apparently regulate the expression of the so-called visual and non-visual opsins, as already demonstrated in higher invertebrate and vertebrate species. Our data confirm that Hydra is a suitable model for studying ancestral precursor of both visual and NVP, providing useful hints on the evolution of visual and photosensory systems.

Jellyfishes-Significant Marine Resources with Potential in the Wound-Healing Process: A Review.

The wound-healing process is a significant area of interest in the medical field, and it is influenced by both external and patient-specific factors. The aim of this review paper is to highlight the proven wound-healing potential of the biocompounds found in jellyfish (such as polysaccharide compounds, collagen, collagen peptides and amino acids). There are aspects of the wound-healing process that can benefit from polysaccharides (JSPs) and collagen-based materials, as these materials have been shown to limit exposure to bacteria and promote tissue regeneration. A second demonstrated benefit of jellyfish-derived biocompounds is their immunostimulatory effects on growth factors such as (TNF-α), (IFN-γ) and (TGF), which are involved in wound healing. A third benefit of collagens and polysaccharides (JSP) is their antioxidant action. Aspects related to chronic wound care are specifically addressed, and within this general theme, molecular pathways related to tissue regeneration are explored in depth. Only distinct varieties of jellyfish that are specifically enriched in the biocompounds involved in these pathways and live in European marine habitats are presented. The advantages of jellyfish collagens over mammalian collagens are highlighted by the fact that jellyfish collagens are not considered transmitters of diseases (spongiform encephalopathy) or various allergic reactions. Jellyfish collagen extracts stimulate an immune response in vivo without inducing allergic complications. More studies are needed to explore more varieties of jellyfish that can be exploited for their biocomponents, which may be useful in wound healing.

Characterization of the Biophysical Properties and Cell Adhesion Interactions of Marine Invertebrate Collagen from Rhizostoma pulmo.

Collagen is the most ubiquitous biomacromolecule found in the animal kingdom and is commonly used as a biomaterial in regenerative medicine therapies and biomedical research. The collagens used in these applications are typically derived from mammalian sources which poses sociological issues due to widespread religious constraints, rising ethical concern over animal rights and the continuous risk of zoonotic disease transmission. These issues have led to increasing research into alternative collagen sources, of which marine collagens, in particular from jellyfish, have emerged as a promising resource. This study provides a characterization of the biophysical properties and cell adhesion interactions of collagen derived from the jellyfish Rhizostoma pulmo (JCol). Circular dichroism spectroscopy and atomic force microscopy were used to observe the triple-helical conformation and fibrillar morphology of JCol. Heparin-affinity chromatography was also used to demonstrate the ability of JCol to bind to immobilized heparin. Cell adhesion assays using integrin blocking antibodies and HT-1080 human fibrosarcoma cells revealed that adhesion to JCol is primarily performed via ß1 integrins, with the exception of α2ß1 integrin. It was also shown that heparan sulfate binding plays a much greater role in fibroblast and mesenchymal stromal cell adhesion to JCol than for type I mammalian collagen (rat tail collagen). Overall, this study highlights the similarities and differences between collagens from mammalian and jellyfish origins, which should be considered when utilizing alternative collagen sources for biomedical research.

Myxozoans (Cnidaria) do not Retain Key Oxygen-Sensing and Homeostasis Toolkit Genes.

For aerobic organisms, both the hypoxia-inducible factor pathway and the mitochondrial genomes are key players in regulating oxygen homeostasis. Recent work has suggested that these mechanisms are not as highly conserved as previously thought, prompting more surveys across animal taxonomic levels, which would permit testing of hypotheses about the ecological conditions facilitating evolutionary loss of such genes. The Phylum Cnidaria is known to harbor wide variation in mitochondrial chromosome morphology, including an extreme example, in the Myxozoa, of mitochondrial genome loss. Because myxozoans are obligate endoparasites, frequently encountering hypoxic environments, we hypothesize that variation in environmental oxygen availability could be a key determinant in the evolution of metabolic gene networks associated with oxygen-sensing, hypoxia-response, and energy production. Here, we surveyed genomes and transcriptomes across 46 cnidarian species for the presence of HIF pathway members, as well as for an assortment of hypoxia, mitochondrial, and stress-response toolkit genes. We find that presence of the HIF pathway, as well as number of genes associated with mitochondria, hypoxia, and stress response, do not vary in parallel to mitochondrial genome morphology. More interestingly, we uncover evidence that myxozoans have lost the canonical HIF pathway repression machinery, potentially altering HIF pathway functionality to work under the specific conditions of their parasitic lifestyles. In addition, relative to other cnidarians, myxozoans show loss of large proportions of genes associated with the mitochondrion and involved in response to hypoxia and general stress. Our results provide additional evidence that the HIF regulatory machinery is evolutionarily labile and that variations in the canonical system have evolved in many animal groups.

Neuropeptides and degenerin/epithelial Na+ channels: a relationship from mammals to cnidarians.

Ion channels of the degenerin (DEG)/epithelial Na+ channel (ENaC) family serve diverse functions ranging from mechanosensation over Na+ reabsorption to H+ sensing and neurotransmission. However, several diverse DEG/ENaCs interact with neuropeptides; some are directly activated, whereas others are modulated by neuropeptides. Two questions arise: does this interaction have a common structural basis and does it have an ancient origin? Current evidence suggests that RFamide neuropeptides activate the FMRFamide-activated Na+ channels (FaNaCs) of invertebrates via binding to a pocket at the external face of their large extracellular domain. It is likely that RFamides might activate DEG/ENaCs from the freshwater polyp Hydra (the HyNaCs) via binding to a similar pocket, although there is not yet any experimental evidence. In contrast, RFamide neuropeptides modulate acid-sensing ion channels (ASICs) from vertebrates via binding to a central cavity enclosed by ß-sheets of the extracellular domain. Dynorphin opioid peptides, for their part, bind to the acidic pocket of ASICs, which might be evolutionarily related to the peptide binding pocket of FaNaCs, but instead of opening the channels they work as antagonists to stabilize its closed state. Moreover, peptides interacting with DEG/ENaCs from animals of different phyla, although having similar sequences, are evolutionarily unrelated to each other. Collectively, it appears that despite a seemingly similar interaction with similar peptides, the interaction of DEG/ENaCs with neuropeptides has diverse structural bases and many origins.

Cloning of Metalloproteinase 17 Genes from Oriental Giant Jellyfish Nemopilema nomurai (Scyphozoa: Rhizostomeae).

We previously demonstrated that Nemopilema nomurai jellyfish venom metalloproteinases (JVMPs) play a key role in the toxicities induced by N. nomurai venom (NnV), including dermotoxicity, cytotoxicity, and lethality. In this study, we identified two full-length JVMP cDNA and genomic DNA sequences: JVMP17-1 and JVMP17-2. The full-length cDNA of JVMP17-1 and 17-2 contains 1614 and 1578 nucleotides (nt) that encode 536 and 525 amino acids, respectively. Putative peptidoglycan (PG) binding, zinc-dependent metalloproteinase, and hemopexin domains were identified. BLAST analysis of JVMP17-1 showed 42, 41, 37, and 37% identity with Hydra vulgaris, Acropora digitifera, Megachile rotundata, and Apis mellifera venom metalloproteinases, respectively. JVMP17-2 shared 38 and 36% identity with H. vulgaris and A. digitifera, respectively. Alignment results of JVMP17-1 and 17-2 with other metalloproteinases suggest that the PG domain, the tissue inhibitor of metalloproteinase (TIMP)-binding surfaces, active sites, and metal (ion)-binding sites are highly conserved. The present study reports the gene cloning of metalloproteinase enzymes from jellyfish species for the first time. We hope these results can expand our knowledge of metalloproteinase components and their roles in the pathogenesis of jellyfish envenomation.

Studying of Molecular Regulation of Developmental Processes of Lower Metazoans Exemplified by Cnidaria Using High-Throughput Sequencing.

A unique set of features and characteristics of species of the Cnidaria phylum is the one reason that makes them a model for a various studies. The plasticity of a life cycle and the processes of cell differentiation and development of an integral multicellular organism associated with it are of a specific scientific interest. A new stage of development of molecular genetic methods, including methods for high-throughput genome, transcriptome, and epigenome sequencing, both at the level of the whole organism and at the level of individual cells, makes it possible to obtain a detailed picture of the development of these animals. This review examines some modern approaches and advances in the reconstruction of the processes of ontogenesis of cnidarians by studying the regulatory signal transduction pathways and their interactions.

Cloning and characterization of Thioredoxin 1 from the Cnidarian Hydra.

Thioredoxins, small disulphide-containing redox proteins, play an important role in the regulation of cellular thiol redox balance through their disulfide reductase activity. In this study, we have identified, cloned, purified and characterized thioredoxin 1 (HvTrx1) from the Cnidarian Hydra vulgaris Ind-Pune. Bioinformatics analysis revealed that HvTrx1 contains an evolutionarily conserved catalytic active site Cys-Gly-Pro-Cys and shows a closer phylogenetic relationship with vertebrate Trx1. Optimum pH and temperature for enzyme activity of purified HvTrx1 was found to be pH 7.0 and 25°C, respectively. Enzyme activity decreased significantly at acidic or alkaline pH as well as at higher temperatures. HvTrx1 was found to be expressed ubiquitously in whole mount in situ hybridization. Treatment of Hydra with hydrogen peroxide (H2O2), a highly reactive oxidizing agent, led to a significant increase in gene expression and enzyme activity of Trx1. Further experiments using PX12, an inhibitor of Trx1, indicated that Trx1 plays an important role in regeneration in Hydra. Finally, by using growth assay in Escherichia coli and wound healing assay in human colon cancer cells, we demonstrate that HvTrx1 is functionally active in both prokaryotic and eukaryotic heterologous systems.

Cnidarian Pattern Recognition Receptor Repertoires Reflect Both Phylogeny and Life History Traits.

Pattern recognition receptors (PRRs) are evolutionarily ancient and crucial components of innate immunity, recognizing danger-associated molecular patterns (DAMPs) and activating host defenses. Basal non-bilaterian animals such as cnidarians must rely solely on innate immunity to defend themselves from pathogens. By investigating cnidarian PRR repertoires we can gain insight into the evolution of innate immunity in these basal animals. Here we utilize the increasing amount of available genomic resources within Cnidaria to survey the PRR repertoires and downstream immune pathway completeness within 15 cnidarian species spanning two major cnidarian clades, Anthozoa and Medusozoa. Overall, we find that anthozoans possess prototypical PRRs, while medusozoans appear to lack these immune proteins. Additionally, anthozoans consistently had higher numbers of PRRs across all four classes relative to medusozoans, a trend largely driven by expansions in NOD-like receptors and C-type lectins. Symbiotic, sessile, and colonial cnidarians also have expanded PRR repertoires relative to their non-symbiotic, mobile, and solitary counterparts. Interestingly, cnidarians seem to lack key components of mammalian innate immune pathways, though similar to PRR numbers, anthozoans possess more complete immune pathways than medusozoans. Together, our data indicate that anthozoans have greater immune specificity than medusozoans, which we hypothesize to be due to life history traits common within Anthozoa. Overall, this investigation reveals important insights into the evolution of innate immune proteins within these basal animals.

Phylogenetic and Selection Analysis of an Expanded Family of Putatively Pore-Forming Jellyfish Toxins (Cnidaria: Medusozoa).

Many jellyfish species are known to cause a painful sting, but box jellyfish (class Cubozoa) are a well-known danger to humans due to exceptionally potent venoms. Cubozoan toxicity has been attributed to the presence and abundance of cnidarian-specific pore-forming toxins called jellyfish toxins (JFTs), which are highly hemolytic and cardiotoxic. However, JFTs have also been found in other cnidarians outside of Cubozoa, and no comprehensive analysis of their phylogenetic distribution has been conducted to date. Here, we present a thorough annotation of JFTs from 147 cnidarian transcriptomes and document 111 novel putative JFTs from over 20 species within Medusozoa. Phylogenetic analyses show that JFTs form two distinct clades, which we call JFT-1 and JFT-2. JFT-1 includes all known potent cubozoan toxins, as well as hydrozoan and scyphozoan representatives, some of which were derived from medically relevant species. JFT-2 contains primarily uncharacterized JFTs. Although our analyses detected broad purifying selection across JFTs, we found that a subset of cubozoan JFT-1 sequences are influenced by gene-wide episodic positive selection compared with homologous toxins from other taxonomic groups. This suggests that duplication followed by neofunctionalization or subfunctionalization as a potential mechanism for the highly potent venom in cubozoans. Additionally, published RNA-seq data from several medusozoan species indicate that JFTs are differentially expressed, spatially and temporally, between functionally distinct tissues. Overall, our findings suggest a complex evolutionary history of JFTs involving duplication and selection that may have led to functional diversification, including variability in toxin potency and specificity.

Sterol Composition of Sponges, Cnidarians, Arthropods, Mollusks, and Echinoderms from the Deep Northwest Atlantic: A Comparison with Shallow Coastal Gulf of Mexico.

Triterpenoid biosynthesis is generally anaerobic in bacteria and aerobic in Eukarya. The major class of triterpenoids in bacteria, the hopanoids, is different to that in Eukarya, the lanostanoids, and their 4,4,14-demethylated derivatives, sterols. In the deep sea, the prokaryotic contribution to primary productivity has been suggested to be higher because local environmental conditions prevent classic photosynthetic processes from occurring. Sterols have been used as trophic biomarkers because primary producers have different compositions, and they are incorporated in primary consumer tissues. In the present study, we inferred food supply to deep sea, sponges, cnidarians, mollusks, crustaceans, and echinoderms from euphotic zone production which is driven by phytoplankton eukaryotic autotrophy. Sterol composition was obtained by gas chromatography and mass spectrometry. Moreover, we compared the sterol composition of three phyla (i.e., Porifera, Cnidaria, and Echinodermata) collected between a deep and cold-water region and a shallow tropical area. We hypothesized that the sterol composition of shallow tropical benthic organisms would better reflect their photoautotrophic sources independently of the taxonomy. Shallow tropical sponges and cnidarians from environments showed plant and zooxanthellae sterols in their tissues, while their deep-sea counterparts showed phytoplankton and zooplankton sterols. In contrast, echinoids, a class of echinoderms, the most complex phylum along with hemichordates and chordates (deuterostomes), did not show significant differences in their sterol profile, suggesting that cholesterol synthesis is present in deuterostomes other than chordates.

Transcriptomic Analysis of Four Cerianthid (Cnidaria, Ceriantharia) Venoms.

Tube anemones, or cerianthids, are a phylogenetically informative group of cnidarians with complex life histories, including a pelagic larval stage and tube-dwelling adult stage, both known to utilize venom in stinging-cell rich tentacles. Cnidarians are an entirely venomous group that utilize their proteinaceous-dominated toxins to capture prey and defend against predators, in addition to several other ecological functions, including intraspecific interactions. At present there are no studies describing the venom for any species within cerianthids. Given their unique development, ecology, and distinct phylogenetic-placement within Cnidaria, our objective is to evaluate the venom-like gene diversity of four species of cerianthids from newly collected transcriptomic data. We identified 525 venom-like genes between all four species. The venom-gene profile for each species was dominated by enzymatic protein and peptide families, which is consistent with previous findings in other cnidarian venoms. However, we found few toxins that are typical of sea anemones and corals, and furthermore, three of the four species express toxin-like genes closely related to potent pore-forming toxins in box jellyfish. Our study is the first to provide a survey of the putative venom composition of cerianthids and contributes to our general understanding of the diversity of cnidarian toxins.

The Complicated Evolutionary Diversification of the Mpeg-1/Perforin-2 Family in Cnidarians.

The invertebrate innate immune system is surprisingly complex, yet our knowledge is limited to a few select model systems. One understudied group is the phylum Cnidaria (corals, sea anemones, etc.). Cnidarians are the sister group to Bilateria and by studying their innate immunity repertoire, a better understanding of the ancestral state can be gained. Corals in particular have evolved a highly diverse innate immune system that can uncover evolutionarily basal functions of conserved genes and proteins. One rudimentary function of the innate immune system is defense against harmful bacteria using pore forming proteins. Macrophage expressed gene 1/Perforin-2 protein (Mpeg-1/P2) is a particularly important pore forming molecule as demonstrated by previous studies in humans and mice, and limited studies in non-bilaterians. However, in cnidarians, little is known about Mpeg-1/P2. In this perspective article, we will summarize the current state of knowledge of Mpeg-1/P2 in invertebrates, analyze identified Mpeg-1/P2 homologs in cnidarians, and demonstrate the evolutionary diversity of this gene family using phylogenetic analysis. We will also show that Mpeg-1 is upregulated in one species of stony coral in response to lipopolysaccharides and downregulated in another species of stony coral in response to white band disease. This data presents evidence that Mpeg-1/P2 is conserved in cnidarians and we hypothesize that it plays an important role in cnidarian innate immunity. We propose that future research focus on the function of Mpeg-1/P2 family in cnidarians to identify its primary role in innate immunity and beyond.

Cell-free scaffold from jellyfish Cassiopea andromeda (Cnidaria; Scyphozoa) for skin tissue engineering.

Disruption of the continuous cutaneous membrane in the integumentary system is considered a health problem of high cost for any nation. Several attempts have been made for developing skin substitutes in order to restore injured tissue including autologous implants and the use of scaffolds based on synthetic and natural materials. Current biomaterials used for skin tissue repair include several scaffold matrices types, synthetic or natural, absorbable, degradable or non-degradable polymers, porous or dense scaffolds, and cells capsulated in hydrogels or spheroids systems so forth. These materials have advantages and disadvantages and its use will depend on the desired application. Recently, marine organisms such as jellyfish have attracted renewed interest, because both its composition and structure resemble the architecture of human dermic tissue. In this context, the present study aims to generate scaffolds from Cassiopea andromeda (C. andromeda), with application in skin tissue engineering, using a decellularization process. The obtained scaffold was studied by infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry analysis (DSC), and scanning electron microscopy (SEM). Crystal violet staining and DNA quantification assessed decellularization effectiveness while the biocompatibility of scaffold was determined with human dermic fibroblasts. Results indicated that the decellularization process reduce native cell population leading to 70% reduction in DNA content. In addition, SEM showed that the macro and microstructure of the collagen I-based scaffold were preserved allowing good adhesion and proliferation of human dermic fibroblasts. The C. andromeda scaffold mimics human skin and therefore represents great potential for skin tissue engineering.

What lies beneath: Hydra provides cnidarian perspectives into the evolution of FGFR docking proteins.

Across the Bilateria, FGF/FGFR signaling is critical for normal development, and in both Drosophila and vertebrates, docking proteins are required to connect activated FGFRs with downstream pathways. While vertebrates use Frs2 to dock FGFR to the RAS/MAPK or PI3K pathways, the unrelated protein, downstream of FGFR (Dof/stumps/heartbroken), fulfills the corresponding function in Drosophila. To better understand the evolution of the signaling pathway downstream of FGFR, the available sequence databases were screened to identify Frs2, Dof, and other key pathway components in phyla that diverged early in animal evolution. While Frs2 homologues were detected only in members of the Bilateria, canonical Dof sequences (containing Dof, ankyrin, and SH2/SH3 domains) were present in cnidarians as well as bilaterians (but not in other animals or holozoans), correlating with the appearance of FGFR. Although these data suggested that Dof coupling might be ancestral, gene expression analysis in the cnidarian Hydra revealed that Dof is not upregulated in the zone of strong FGFRa and FGFRb expression at the bud base, where FGFR signaling controls detachment. In contrast, transcripts encoding other, known elements of FGFR signaling in Bilateria, namely the FGFR adaptors Grb2 and Crkl, which are acting downstream of Dof (and Frs2), as well as the guanyl nucleotide exchange factor Sos, and the tyrosine phosphatase Csw/Shp2, were strongly upregulated at the bud base. Our expression analysis, thus, identified transcriptional upregulation of known elements of FGFR signaling at the Hydra bud base indicating a highly conserved toolkit. Lack of transcriptional Dof upregulation raises the interesting question, whether Hydra FGFR signaling requires either of the docking proteins known from Bilateria.

Size and density of upside-down jellyfish, Cassiopea sp., and their impact on benthic fluxes in a Caribbean lagoon.

Anthropogenic disturbances may be increasing jellyfish populations globally. Epibenthic jellyfish are ideal organisms for studying this phenomenon due to their sessile lifestyle, broad geographic distribution, and prevalence in near-shore coastal environments. There are few studies, however, that have documented epibenthic jellyfish abundance and measured their impact on ecological processes in tropical ecosystems. In this study, the density and size of the upside-down jellyfish (Cassiopea spp.) were measured in Codrington Lagoon, Barbuda. A sediment core incubation study, with and without Cassiopea, also was performed to determine their impact on benthic oxygen and nutrient fluxes. Densities of Cassiopea were 24-168 m-2, among the highest reported values in the literature. Under illuminated conditions, Cassiopea increased oxygen production >300% compared to sediment alone, and they changed sediments from net heterotrophy to net autotrophy. Cassiopea increased benthic ammonium uptake, but reduced nitrate uptake, suggesting they can significantly alter nitrogen cycling. Future studies should quantify the abundance of Cassiopea and measure their impacts on ecosystem processes, in order to further determine how anthropogenic-related changes may be altering the function of tropical coastal ecosystems.

Dynamic Evolution of the Cthrc1 Genes, a Newly Defined Collagen-Like Family.

Collagen triple helix repeat containing protein 1 (Cthrc1) is a secreted glycoprotein reported to regulate collagen deposition and to be linked to the Transforming growth factor ß/Bone morphogenetic protein and the Wnt/planar cell polarity pathways. It was first identified as being induced upon injury to rat arteries and was found to be highly expressed in multiple human cancer types. Here, we explore the phylogenetic and evolutionary trends of this metazoan gene family, previously studied only in vertebrates. We identify Cthrc1 orthologs in two distant cnidarian species, the sea anemone Nematostella vectensis and the hydrozoan Clytia hemisphaerica, both of which harbor multiple copies of this gene. We find that Cthrc1 clade-specific diversification occurred multiple times in cnidarians as well as in most metazoan clades where we detected this gene. Many other groups, such as arthropods and nematodes, have entirely lost this gene family. Most vertebrates display a single highly conserved gene, and we show that the sequence evolutionary rate of Cthrc1 drastically decreased within the gnathostome lineage. Interestingly, this reduction coincided with the origin of its conserved upstream neighboring gene, Frizzled 6 (FZD6), which in mice has been shown to functionally interact with Cthrc1. Structural modeling methods further reveal that the yet uncharacterized C-terminal domain of Cthrc1 is similar in structure to the globular C1q superfamily domain, also found in the C-termini of collagens VIII and X. Thus, our studies show that the Cthrc1 genes are a collagen-like family with a variable short collagen triple helix domain and a highly conserved C-terminal domain structure resembling the C1q family.

Boundary maintenance in the ancestral metazoan Hydra depends on histone acetylation.

Much of boundary formation during development remains to be understood, despite being a defining feature of many animal taxa. Axial patterning of Hydra, a member of the ancient phylum Cnidaria which diverged prior to the bilaterian radiation, involves a steady-state of production and loss of tissue, and is dependent on an organizer located in the upper part of the head. We show that the sharp boundary separating tissue in the body column from head and foot tissue depends on histone acetylation. Histone deacetylation disrupts the boundary by affecting numerous developmental genes including Wnt components and prevents stem cells from entering the position dependent differentiation program. Overall, our results suggest that reversible histone acetylation is an ancient regulatory mechanism for partitioning the body axis into domains with specific identity, which was present in the common ancestor of cnidarians and bilaterians, at least 600 million years ago.

сWnt signaling modulation results in a change of the colony architecture in a hydrozoan.

At the polyp stage, most hydrozoan cnidarians form highly elaborate colonies with a variety of branching patterns, which makes them excellent models for studying the evolutionary mechanisms of body plan diversification. At the same time, molecular mechanisms underlying the robust patterning of the architecturally complex hydrozoan colonies remain unexplored. Using non-model hydrozoan Dynamena pumila we showed that the key components of the Wnt/ß-catenin (cWnt) pathway (ß-catenin, TCF) and the cWnt-responsive gene, brachyury 2, are involved in specification and patterning of the developing colony shoots. Strikingly, pharmacological modulation of the cWnt pathway leads to radical modification of the monopodially branching colony of Dynamena which acquire branching patterns typical for colonies of other hydrozoan species. Our results suggest that modulation of the cWnt signaling is the driving force promoting the evolution of the vast variety of the body plans in hydrozoan colonies and offer an intriguing possibility that the involvement of the cWnt pathway in the regulation of branching morphogenesis might represent an ancestral feature predating the cnidarian-bilaterian split.