Stimulation of protein (collagen) synthesis in sponge cells by a cardiac myotrophin-related molecule from Suberites domuncula

Collagenic architecture and morphotraits in a marine basal metazoan as a model for bioinspired applied research

In some Porifera (Demospongiae: Keratosa), prototypes of the connective system are almost exclusively based on collagenic networks. We studied the topographic distribution, spatial layout, microtraits, and/or morphogenesis of these collagenic structures in Ircinia retidermata (Dictyoceratida: Irciniidae). Analyses were carried out on a clonal strain from sustainable experimental mariculture by using light and scanning electron microscopy. Histology revealed new insights on the widely diversified and complex hierarchical assemblage of collagenic structures. Key evolutionary novelties in the organization of sponge connective system were found out. The aquiferous canals are shaped as corrugate‐like pipelines conferring plasticity to the water circulation system. Compact clusters of elongated cells are putatively involved in a nutrient transferring system. Knob‐ended filaments are characterized by a banding pattern and micro‐components. Ectosome and outer endosome districts are the active fibrogenetic areas, where exogenous material constitutes an axial condensation nucleus for the ensuing morphogenesis. The new data can be useful to understand not only the evolutionary novelties occurring in the target taxon but also the morpho‐functional significance of its adaptive collagenic anatomical traits. In addition, data may give insights on both marine collagen sustainable applied researches along with evolutionary and phylogenetic analyses, thus highlighting sponges as a key renewable source for inspired biomaterials. Therefore, we also promote bioresources sustainable exploitation with the aim to provide new donors of marine collagen, thereby supporting conservation of wild populations/species.

Hierarchical architecture of sponge spicules: biocatalytic and structure-directing activity of silicatein proteins as model for bioinspired applications

Since the first description of the silicateins, a group of enzymes that mediate the formation of the amorphous, hydrated biosilica of the skeleton of the siliceous sponges, much progress has been achieved in the understanding of this biomineralization process. These discoveries include, beside the proof of the enzymatic nature of the sponge biosilica formation, the dual property of the enzyme, to act both as a structure-forming and structure-guiding protein, and the demonstration that the initial product of silicatein is a soft, gel-like material that has to undergo a maturation process during which it achieves its favorable physical-chemical properties allowing the development of various technological or medical applications. This process comprises the hardening of the material by the removal of water and ions, its cast-molding to specific morphologies, as well as the fusion of the biosilica nanoparticles through a biosintering mechanism. The discovery that the enzymatically formed biosilica is morphogenetically active and printable also opens new applications in rapid prototyping and three-dimensional bioprinting of customized scaffolds/implants for biomedical use.

Modeling biosilicification at subcellular scales

Biosilicification occurs in many organisms. Sponges and diatoms are major examples of them. In this chapter, we introduce a modeling approach that describes several biological mechanisms controlling silicification. Modeling biosilicification is a typical multiscale problem where processes at very different temporal and spatial scales need to be coupled: processes at the molecular level, physiological processes at the subcellular and cellular level, etc. In biosilicification morphology plays a fundamental role, and a spatiotemporal model is required. In the case of sponges, a particle simulation based on diffusion-limited aggregation is presented here. This model can describe fractal properties of silica aggregates in first steps of deposition on an organic template. In the case of diatoms, a reaction-diffusion model is introduced which can describe the concentrations of chemical components and has the possibility to include polymerization chain of reactions.

Biosilica: Molecular Biology, Biochemistry and Function in Demosponges as well as its Applied Aspects for Tissue Engineering

Biomineralization, biosilicification in particular (i.e. the formation of biogenic silica, SiO(2)), has become an exciting source of inspiration for the development of novel bionic approaches following 'nature as model'. Siliceous sponges are unique among silica-forming organisms in their ability to catalyze silica formation using a specific enzyme termed silicatein. In this study, we review the present state of knowledge on silicatein-mediated 'biosilica' formation in marine demosponges, the involvement of further molecules in silica metabolism and their potential applications in nano-biotechnology and bio-medicine. While most forms of multicellular life have developed a calcium-based skeleton, a few specialized organisms complement their body plan with silica. Only sponges (phylum Porifera) are able to polymerize silica enzymatically mediated in order to generate massive siliceous skeletal elements (spicules) during a unique reaction, at ambient temperature and pressure. During this biomineralization process (i.e. biosilicification), hydrated, amorphous silica is deposited within highly specialized sponge cells, ultimately resulting in structures that range in size from micrometres to metres. This peculiar phenomenon has been comprehensively studied in recent years, and in several approaches, the molecular background was explored to create tools that might be employed for novel bioinspired biotechnological and biomedical applications. Thus, it was discovered that spiculogenesis is mediated by the enzyme silicatein and starts intracellularly. The resulting silica nanoparticles fuse and subsequently form concentric lamellar layers around a central protein filament, consisting of silicatein and the scaffold protein silintaphin-1. Once the growing spicule is extruded into the extracellular space, it obtains final size and shape. Again, this process is mediated by silicatein and silintaphin-1/silintaphin-1, in combination with other molecules such as galectin and collagen. The molecular toolbox generated so far allows the fabrication of novel micro- and nano-structured composites, contributing to the economical and sustainable synthesis of biomaterials with unique characteristics. In this context, first bioinspired approaches implement recombinant silicatein and silintaphin-1 for applications in the field of biomedicine (biosilica-mediated regeneration of tooth and bone defects) with promising results.

Mechanisms of cardiogenesis in cardiovascular progenitor cells

Self-renewing cells of the vertebrate heart have become a major subject of interest in the past decade. However, many researchers had a hard time to argue against the orthodox textbook view that defines the heart as a postmitotic organ. Once the scientific community agreed on the existence of self-renewing cells in the vertebrate heart, their origin was again put on trial when transdifferentiation, dedifferentiation, and reprogramming could no longer be excluded as potential sources of self-renewal in the adult organ. Additionally, the presence of self-renewing pluripotent cells in the peripheral blood challenges the concept of tissue-specific stem and progenitor cells. Leaving these unsolved problems aside, it seems very desirable to learn about the basic biology of this unique cell type. Thus, we shall here paint a picture of cardiovascular progenitor cells including the current knowledge about their origin, basic nature, and the molecular mechanisms guiding proliferation and differentiation into somatic cells of the heart.

Interaction of the retinoic acid signaling pathway with spicule formation in the marine sponge Suberites domuncula through activation of bone morphogenetic protein-1

BACKGROUND

The formation of the spicules in siliceous sponges involves the formation of cylinder-like structures in the extraspicular space, composed of the enzyme silicatein and the calcium-dependent lectin.

SCOPE OF REVIEW

Molecular cloning of the cDNAs (carotene dioxygenase, retinal dehydrogenase, and BMB-1 [bone morphogenic protein-1]) from the demosponge Suberites domuncula was performed. These tools were used to understand the retinoid metabolism in the animal by qRT-PCR, immunoblotting and TEM.

MAJOR CONCLUSIONS

We demonstrate that silintaphin-2, a silicatein-interacting protein, is processed from a longer-sized 15-kDa precursor to a truncated, shorter-sized 13kDa calcium-binding protein via proteolytic cleavage at the dipeptide Ala↓Asp, mediated by BMP-1. The expression of this protease as well as the expression of two key enzymes of the carotinoid metabolism, the β,β-carotene-15,15'-dioxygenase and the retinal dehydrogenase/reductase, were found to be strongly up-regulated by retinoic acid. Hence retinoic acid turned out to be a key factor in skeletogenesis in the most ancient still existing metazoans, the sponges.

GENERAL SIGNIFICANCE

It is shown that retinoic acid regulates the formation of the organic cylinder that surrounds the axis of the spicules and enables, as a scaffold, the radial apposition of new silica layers and hence the growth of the spicules.

Inorganic polymeric phosphate/polyphosphate as an inducer of alkaline phosphatase and a modulator of intracellular Ca2+ level in osteoblasts (SaOS-2 cells) in vitro

Inorganic polymeric phosphate is a physiological polymer that accumulates in bone cells. In the present study osteoblast-like SaOS-2 cells were exposed to this polymer, complexed in a 2:1 stoichiometric ratio with Ca(2+), polyP (Ca(2+) salt). At a concentration of 100 μM, polyP (Ca(2+) salt) caused a strong increase in the activity of the alkaline phosphatase and also an induction of the steady-state expression of the gene encoding this enzyme. Comparative experiments showed that polyP (Ca(2+) salt) can efficiently replace β-glycerophosphate in the in vitro hydroxyapatite (HA) biomineralization assay. In the presence of polyP (Ca(2+) salt) the cells extensively form HA crystallites, which remain intimately associated with or covered by the plasma membrane. Only the tips of the crystallites are directly exposed to the extracellular space. Element mapping by scanning electron microscopy/energy-dispersive X-ray spectroscopy coupled to a silicon drift detector supported the finding that organic material was dispersed within the crystallites. Finally, polyP (Ca(2+) salt) was found to cause an increase in the intracellular Ca(2+) level, while polyP, as well as inorganic phosphate (P(i)) or Ca(2+) alone, had no effect at the concentrations used. These findings are compatible with the assumption that polyP (Ca(2+) salt) is locally, on the surface of the SaOS-2 cells, hydrolyzed to P(i) and Ca(2+). We conclude that the inorganic polymer polyP (Ca(2+) salt) in concert with a second inorganic, and physiologically occurring, polymer, biosilica, activates osteoblasts and impairs the maturation of osteoclasts.

Biosilica-based strategies for treatment of osteoporosis and other bone diseases

Osteoporosis is a common disease in later life, which has become a growing public health problem. This degenerative bone disease primarily affects postmenopausal women, but also men may suffer from reduced bone mineral density. The development of prophylactic treatments and medications of osteoporosis has become an urgent issue due to the increasing proportion of the elderly in the population. Apart from medical/hormonal treatments, current strategies for prophylaxis of osteoporosis are primarily based on calcium supplementation as a main constituent of bone hydroxyapatite mineral. Despite previous reports suggesting an essential role in skeletal growth and development, the significance of the trace element silicon in human bone formation has attracted major scientific interest only rather recently. The interest in silicon has been further increased by the latest discoveries in the field of biosilicification, the formation of the inorganic silica skeleton of the oldest still extant animals on Earth, the sponges, which revealed new insights in the biological function of this element. Sponges make use of silicon to build up their inorganic skeleton which consists of biogenously formed polymeric silica (biosilica). The formation of biosilica is mediated by specific enzymes, silicateins, which have been isolated, characterized, and expressed in a recombinant way. Epidemiological studies revealed that dietary silicon reduces the risk of osteoporosis and other bone diseases. Recent results allowed for the first time to understand the molecular mechanism underlying the protective effect of silicic acid/biosilica against osteoporosis. Biosilica was shown to modulate the ratio of expression of two cytokines involved in bone formation-RANKL and osteoprotegerin. Hence, biosilica has been proposed to have a potential in prophylaxis and therapy of osteoporosis and related bone diseases.

The stem cell system in demosponges: insights into the origin of somatic stem cells

The stem cell system is one of the unique systems that have evolved only in multicellular organisms. Major questions about this system include what type(s) of stem cells are involved (pluri-, multi- or uni-potent stem cells), and how the self-renewal and differentiation of stem cells are regulated. To understand the origin of the stem cell system in metazoans and to get insights into the ancestral stem cell itself, it is important to discover the molecular and cellular mechanisms of the stem cell system in sponges (Porifera), the evolutionarily oldest extant metazoans. Histological studies here provided a body of evidence that archeocytes are the stem cells in sponges, and recent molecular studies of sponges, especially the finding of the expression of Piwi homologues in archeocytes and choanocytes in a freshwater sponge, Ephydatia fluviatilis, have provided critical insights into the stem cell system in demosponges. Here I introduce archeocytes and discuss (i) modes of archeocyte differentiation, (ii) our current model of the stem cell system in sponges composed of both archeocytes and choanocytes based on our molecular analysis and previous microscopic studies suggesting the maintenance of pluripotency in choanocytes, (iii) the inference that the Piwi and piRNA function in maintaining stem cells (which also give rise to gametes) may have already been achieved in the ancestral metazoan, and (iv) possible hypotheses about how the migrating stem cells arose in the urmetazoan (protometazoan) and about the evolutionary origin of germline cells in the urbilaterian (protobilaterian).

An overview of silica in biology: its chemistry and recent technological advances

Biomineralisation is widespread in the biological world and occurs in bacteria, single-celled protists, plants, invertebrates and vertebrates. Minerals formed in the biological environment often show unusual physical properties (e.g. strength, degree of hydration) and often have structures that exhibit order on many length scales. Biosilica, found in single cell organisms through to higher plants and primitive animals (sponges), is formed from an environment that is undersaturated with respect to silicon and under conditions of around neutral pH and low temperature, ca. 4-40 degrees C. Formation of the mineral may occur intra- or extra-cellularly, and specific biochemical locations for mineral deposition that include lipids, proteins and carbohydrates are known. In most cases, the formation of the mineral phase is linked to cellular processes, understanding of which could lead to the design of new materials for biomedical, optical and other applications. This Chapter briefly describes the occurrence of silica in biology including known roles for the mineral phase, the chemistry of the material, the associated biomolecules and some recent applications of this knowledge in materials chemistry.The terminology which is used in this and other contributions within this volume is as follows: Si: the chemical symbol for the element and the generic term used when the nature of the specific silicon compound is not known. Si(OH) ( 4 ): orthosilicic acid, the fundamental building block used in the formation of silicas. SiO ( 2 ) x nH ( 2 ) O or SiO ( 2-x ) (OH) ( 2x ) x 2H ( 2 ) O: amorphous, hydrated, polymerised material. Oligomerisation: the formation of dimers and small oligomers from orthosilicic acid by removal of water. For example, 2Si(OH)(4) <--> (HO)(3)Si-O-Si(OH)(3) + H(2)O Polymerisation: the mutual condensation of silicic acid to give molecularly coherent units of increasing size. Organosilicon compound: must contain silicon covalently bonded to carbon within a distinct chemical species Silane: a compound having silicon atom(s) and organic chemical groups often connected through an oxygen linkage; e.g. tetrethoxy or tetramethoxysilane Silanol: hydroxyl group bonded to silicon atom Silicate: a chemically specific ion having negative charge (e.g. [Formula: see text]), term also used to describe salts (e.g. sodium silicate Na(2)SiO(3)) Opal: the term used to describe the gem-stone and often used to describe the type of amorphous silica produced by biological organisms. The two are similar in structure at the molecular level (disordered or amorphous), but at higher levels of structural organisation are distinct from one another.

Analysis of the axial filament in spicules of the demosponge Geodia cydonium: Different silicatein composition in microscleres (asters) and megascleres (oxeas and triaenes)

The skeleton of the siliceous sponges (Porifera: Hexactinellida and Demospongiae) is supported by spicules composed of bio-silica. In the axial canals of megascleres, harboring the axial filaments, three isoforms of the enzyme silicatein (-alpha, -beta and -gamma) have been identified until now, using the demosponges Tethya aurantium and Suberites domuncula. Here we describe the composition of the proteinaceous components of the axial filament from small spicules, the microscleres, in the demosponge Geodia cydonium that possesses megascleres and microscleres. The morphology of the different spicule types is described. Also in G. cydonium the synthesis of the spicules starts intracellularly and they are subsequently extruded to the extracellular space. In contrast to the composition of the silicateins in the megascleres (isoforms: -alpha, -beta and -gamma), the axial filaments of the microscleres contain only one form of silicatein, termed silicatein-alpha/beta, with a size of 25kDa. Silicatein-alpha/beta undergoes three phosphorylation steps. The gene encoding silicatein-alpha/beta was identified and found to comprise the same characteristic sites, described previously for silicateins-alpha or -beta. It is hypothesized, that the different composition of the axial filaments, with respect to silicateins, contributes to the morphology of the different types of spicules.

Regional and modular expression of morphogenetic factors in the demosponge Lubomirskia baicalensis

Some sponges [phylum Porifera], e.g. the demosponges Lubomirskia baicalensis or Axinella polypoides, show an arborescent growth form. In the freshwater sponge L. baicalensis this morphotype is seen mostly in depths below 4m while in more shallow regions it grows as a crust. The different growth forms are determined in nature very likely by water current and/or light. The branches of this species are composed of modules, arranged along the apical-basal axis. The modules are delimited by a precise architecture of the spicule bundles; longitudinal bundles originate from the apex of the earlier module, while at the basis of each module these bundles are cross-linked by traverse bundles under formation of annuli. Genes encoding putative morphogenetic factors, myotrophin and epidermal growth factor (EGF)-like molecules, and one gene of an antagonist for the Wnt signaling pathway, the soluble frizzled molecule, have been identified and characterized. Their expression levels as well as those of silicatein, one major spicule-forming molecule, have been studied in the crusts and the modules. The data revealed that at the apices of each module higher level of expression of myotrophin and EGF can be detected, while the base of each module is characterized by a high steady-state expression level of soluble frizzled molecule. These results suggest that module formation in L. baicalensis is controlled by a tuned interaction of agonistic (e.g., myotrophin and EGF) as well as antagonistic morphogenetic factors (e.g., soluble frizzled molecule).

Enzymatic production of biosilica glass using enzymes from sponges: basic aspects and application in nanobiotechnology (material sciences and medicine)

Biomineralization, biosilicification in particular (i.e. the formation of biogenic silica, SiO2), has become an exciting source of inspiration for the development of novel bionic approaches following "nature as model". Siliceous sponges are unique among silica forming organisms in their ability to catalyze silica formation using a specific enzyme termed silicatein. In this study, we review the present state of knowledge on silicatein-mediated "biosilica" formation in marine sponges, the involvement of further molecules in silica metabolism and their potential application in nanobiotechnology and medicine.

The stem cell concept in sponges (Porifera): Metazoan traits

Sponges are considered the oldest living animal group and provide important insights into the earliest evolutionary processes in the Metazoa. This paper reviews the evidence that sponge stem cells have essential roles in cellular specialization, embryogenesis and Bauplan formation. Data indicate that sponge archaeocytes not only represent germ cells but also totipotent stem cells. Marker genes have been identified which are expressed in totipotent stem cells and gemmule cells. Furthermore, genes are described for the three main cell lineages in sponge, which share a common origin from archaeocytes and result in the differentiation of skeletal, epithelial, and contractile cells.

Co-expression and functional interaction of silicatein with galectin: matrix-guided formation of siliceous spicules in the marine demosponge Suberites domuncula

Sponges (phylum Porifera) of the class of Demospongiae are stabilized by a siliceous skeleton. It is composed of silica needles (spicules), which provide the morphogenetic scaffold of these metazoans. In the center of the spicules there is an axial filament that consists predominantly of silicatein, an enzyme that catalyzes the synthesis of biosilica. By differential display of transcripts we identified additional proteins involved in silica formation. Two genes were isolated from the marine demosponge Suberites domuncula; one codes for a galectin and the other for a fibrillar collagen. The galectin forms aggregates to which silicatein molecules bind. The extent of the silicatein-mediated silica formation strongly increased if associated with the galectin. By applying a new and mild extraction procedure that avoids hydrogen fluoride treatment, native axial filaments were extracted from spicules of S. domuncula. These filaments contained, in addition to silicatein, the galectin and a few other proteins. Immunogold electron microscopic studies underscored the role of these additional proteins, in particular that of galectin, in spiculogenesis. Galectin, in addition to silicatein, presumably forms in the axial canal as well as on the surface of the spicules an organized net-like matrix. In the extraspicular space most of these complexes are arranged concentrically around the spicules. Taken together, these additional proteins, working together with silicatein, may also be relevant for potential (nano)-biotechnological applications of silicatein in the formation of surface coatings. Finally, we propose a scheme that outlines the matrix (galectin/silicatein)-guided appositional growth of spicules through centripetal and centrifugal synthesis and deposition of biosilica.

Evolution of the heart from bacteria to man

This review provides an overview of the evolutionary path to the mammalian heart from the beginnings of life (about four billion years ago ) to the present. Essential tools for cellular homeostasis and for extracting and burning energy are still in use and essentially unchanged since the appearance of the eukaryotes. The primitive coelom, characteristic of early multicellular organisms ( approximately 800 million years ago), is lined by endoderm and is a passive receptacle for gas exchange, feeding, and sexual reproduction. The cells around this structure express genes homologous to NKX2.5/tinman, and gradual specialization of this "gastroderm" results in the appearance of mesoderm in the phylum Bilateria, which will produce the first primitive cardiac myocytes. Investment of the coelom by these mesodermal cells forms a "gastrovascular" structure. Further evolution of this structure in the bilaterian branches Ecdysoa (Drosophila) and Deuterostoma (amphioxus) culminate in a peristaltic tubular heart, without valves, without blood vessels or blood, but featuring a single layer of contracting mesoderm. The appearance of Chordata and subsequently the vertebrates is accompanied by a rapid structural diversification of this primitive linear heart: looping, unidirectional circulation, an enclosed vasculature, and the conduction system. A later innovation is the parallel circulation to the lungs, followed by the appearance of septa and the four-chambered heart in reptiles, birds, and mammals. With differentiation of the cardiac chambers, regional specialization of the proteins in the cardiac myocyte can be detected in the teleost fish and amphibians. In mammals, growth constraints are placed on the heart, presumably to accommodate the constraints of the body plan and the thoracic cavity, and adult cardiac myocytes lose the ability to re-enter the cell cycle on demand. Mammalian cardiac myocyte innervation betrays the ancient link between the heart, the gut, and reproduction: the vagus nerve controlling heart rate emanates from centers in the central nervous system regulating feeding and affective behavior.

Expression pattern of the Brachyury and Tbx2 homologues from the sponge Suberites domuncula

BACKGROUND INFORMATION

T-box transcription factors are a large family of transcriptional regulators involved in many aspects of embryonic development. In a previous report, we described the isolation and genomic characterization of two T-box genes from the siliceous sponge Suberites domuncula: a Brachyury homologue, Sd-Bra, and a Tbx2 homologue, Sd-Tbx2. Elucidation of the genomic structure of Sd-Bra allowed us to demonstrate the existence of two different isoforms, resulting from alternative splicing. Moreover, we demonstrated that the shorter isoform exists in two different glycosylation states.

RESULTS

In the present study, we demonstrate a differential subcellular localization of the three Sd-Bra isoforms, suggesting that its differential nuclear import could be an important mechanism for its functional regulation. Furthermore, we demonstrate that Sd-Tbx2 exists only in one isoform, which is mainly localized in the nucleus. The pattern of expression of Sd-Bra and Sd-Tbx2 genes is analysed in sponge tissue, in gemmules and in cultured cells.

CONCLUSION

These results suggest a conserved role for Sd-Bra in the control of morphogenetic movements through the regulation of cell-adhesion properties and the involvement of Sd-Tbx2 in the determination of cell identity in the early stages of differentiation, reminiscent of the function of Tbx2-3-4-5 in vertebrates during limb specification. Also, the fact that a Brachyury and a Tbx2 homologue exist in S. domuncula suggests that the first divergence from the ancestral Brachyury-like gene might be a Tbx2-like gene and not a Tbrain-like gene as had been previously suggested.

Approaches for a sustainable use of the bioactive potential in sponges: analysis of gene clusters, differential display of mRNA and DNA chips

In recent years, analyses of the genome organization of marine sponges have begun that have led to the elucidation of selected genes and gene arrangements that exist in gene clusters (e.g. the receptor tyrosine kinase cluster and the allograft inflammatory factor cluster). Most of these studies were performed with the demosponge Suberites domuncula; but Geodia cydonium (Demospongiae), Aphrocallistes vastus (Hexactinellida) and Sycon raphanus (Calcarea) were also investigated. Both S. domuncula and G. cydonium possess a surprisingly large genome of approximately 1.7 pg DNA per haploid set. Taking the high gene density in these sponges into account and considering that predominantly single-copy DNA exists, the gene number of S. domuncula and G. cydonium was estimated to be approximately 300,000. Presumably, the large gene number in the sponge genome is due to regional gene duplication; so far evidence for a transposition in sponges has been presented. Data indicate that only 0.25 % of the total sponge genome comprises CA/TG microsatellites, and until now also no SINEs/transposable elements have been identified. Due to the rapid progress in the field of molecular biology of sponges the application of sponge genes for expression studies by DNA-array techniques (microarray) has become possible. These achievements will be further supported by the systematic analysis of the expressed genome of sponges; the results will be (partially) released (http://spongebase.uni-mainz.de/cgi-bin/blast/blastserver.cgi). In our efforts employing the results from the analysis of the genome to molecular biotechnology, we applied the technique of differential display of mRNA. One example, the effect of silicate on gene expression in S. domuncula, is outlined here. Future results will allow the identification of the genes involved in the synthesis of bioactive compounds from sponges [Porifera]. This progress will contribute considerably to a fruitful and fast development in the field of molecular marine biotechnology.

Evolution of metazoan cell junction proteins: the scaffold protein MAGI and the transmembrane receptor tetraspanin in the demosponge Suberites domuncula

Until recently the positioning of the sponges (phylum Porifera) within the metazoan systematics was hampered by the lack of molecular evidence for the existence of junctional structures in the surface cell layers. In this study two genes related to the tight junctions are characterized from the demosponge Suberites domuncula: tetraspanin (SDTM4SF), a cell surface receptor, and MAGI (SDMAGI), a MAGUK (membrane-associated guanylate kinase homologue) protein. Especially the MAGI protein is known in other metazoan animal phyla to exist exclusively in tight junctions. The characteristic domains of MAGI proteins (six PDZ domains, two WW domains, and a truncated guanylate kinase motif) are conserved in the sponge protein. The functional analysis of SDMAGI done by in situ hybridization shows its expression in the surface epithelial layers (exopinacoderm and endopinacoderm). Northern blot studies reveal that expression of SDMAGI and SDTM4SF increases after formation of the pinacoderm layer in the animals as well as in primmorphs. These results support earlier notions that sponges contain junctional structures. We conclude that sponges contain epithelia whose cells are organized by cell junctions.

Mineralization of SaOS-2 cells on enzymatically (silicatein) modified bioactive osteoblast-stimulating surfaces

There is a demand for novel bioactive supports in surgery, orthopedics, and tissue engineering. The availability of recombinant silica-synthesizing enzyme (silicatein) opens new possibilities for the synthesis of silica-containing bioactive surfaces under ambient conditions that do not damage biomolecules like proteins. Here it is shown that growth of human osteosarcoma SaOS-2 cells on cluster plates precoated with Type 1 collagen is not affected by additional coating of the plates with the recombinant silicatein and incubation with its enzymatic substrate, tetraethoxysilane (TEOS). However, the enzymatic modification of the plates by biosilica deposition on the protein-coated surface caused a marked increase in calcium phosphate formation of SaOS-2 cells as revealed by alizarin red-S staining to quantify calcium mineral content. The increased occurrence of calcium-phosphate nodules on the modified surface was also observed by scanning electron microscopy. These results suggest that by supporting calcium-phosphate deposition in vitro, biosilica (silicatein)-modified surfaces are potentially bioactive in vivo, by stimulating osteoblast mineralization function.

Matrix-mediated canal formation in primmorphs from the sponge Suberites domuncula involves the expression of a CD36 receptor-ligand system

Sponges (Porifera), represent the phylogenetically oldest metazoan phylum still extant today. Recently, molecular biological studies provided compelling evidence that these animals share basic receptor/ligand systems, especially those involved in bodyplan formation and in immune recognition, with the higher metazoan phyla. An in vitro cell/organ-like culture system, the primmorphs, has been established that consists of proliferating and differentiating cells, but no canals of the aquiferous system. We show that after the transfer of primmorphs from the demosponge Suberites domuncula to a homologous matrix (galectin), canal-like structures are formed in these 3D-cell aggregates. In parallel with the formation of these structures a gene is expressed whose deduced protein falls into the CD36/LIMPII receptor family. The receptor was cloned and found to be strongly expressed after adhesion to the galectin matrix. This process was suppressed if primmorphs were co-incubated with a homologous polypeptide containing the CSVTCG domain, as found in thrombospondin-1 (and related) molecules of vertebrates. In situ hybridization studies revealed that the S. domuncula CD36/LIMPII receptor is localized in the pinacocytes that surround the canals of the sponge. Furthermore, a secondary metabolite from a sponge-associated bacterium was isolated and characterized, the 2-methylthio-1,4-naphthoquinone (MTN). MTN causes inhibition of cell proliferation of vertebrate tumor cells at concentrations of >80 ng/ml. However, doses of only 2 ng are required to potently inhibit angiogenesis in the chick chorio-allantoic membrane assay. At concentrations of 10 ng/ml this compound was also found to suppress the expression of the S. domuncula CD36/LIMPII; this result is a first indication that this secondary metabolite has a conserved functional activity: the suppression of the formation of the circulation system, from sponges to vertebrates.

The molecular basis for the evolution of the metazoan bodyplan: extracellular matrix-mediated morphogenesis in marine demosponges

Molecular data on development/differentiation and on comparative genomics allow insights into the genetic basis of the evolution of a bodyplan. Sponges (phylum Porifera) are animals that are the (still extant) stem group with the hypothetical Urmetazoa as the earliest common ancestor of all metazoans; they possess the basic features of the characteristic metazoan bodyplan also valid for the animals of the crown taxa. Here we describe three homeobox genes from the demosponge Suberites domuncula whose deduced proteins (HOXa1_SUBDO, HOXb1_SUBDO, HOXc1_SUBDO) are to be grouped with the Antennapedia class of homeoproteins (subclasses TIx-Hox11 and NK-2). In addition, a cDNA encoding a LIM/homeobox protein has been isolated which comprises high sequence similarity to the related LIM homeodomain (HD) proteins in its LIM as well as in its HD domains. To elucidate the potential function of these proteins in the sponge a new in vitro system was developed. Primmorphs which are formed from dissociated cells were grown on a homologous galectin matrix. This galectin cDNA was cloned and the recombinant protein was used for the preparation of the matrix. The galectin/polylysine matrix induced in primmorphs the formation of channels, one major morphogenetic process in sponges. Under such conditions the expression of the gene encoding the LIM/homeobox protein is strongly upregulated, while the expression of the other homeobox genes remains unchanged or is even downregulated. Competition experiments with galactosylceramides isolated from S. domuncula were performed. They revealed that a beta-galactosylceramide, named Sdgal-1, prevented the expression of the LIM gene on the galectin matrix, while Sdgal-2, a diglycosylceramide having a terminal alpha-glycosidically linked galactose, caused no effect on the formation of channels in primmorphs or on LIM expression. This study demonstrates for the first time that an extracellular matrix molecule, galectin, induces a morphogenetic process in sponges which is very likely caused by a LIM/homeobox protein. Furthermore, a new model is introduced (galectin-caused channel formation in sponge primmorphs) to investigate basic pathways, thus allowing new insights into the functional molecular evolution of Metazoa.

Porifera a reference phylum for evolution and bioprospecting: the power of marine genomics

The term Urmetazoa, as the hypothetical metazoan ancestor, was introduced to highlight the finding that all metazoan phyla including the Porifera [sponges] derived from one common ancestor. Analyses of sponge genomes, from Demospongiae, Calcarea and Hexactinellida have permitted the reconstruction of the evolutionary trail from Fungi to Metazoa. This has provided evidence that the characteristic evolutionary novelties of Metazoa existing in Porifera share high sequence similarities and in some aspects also functional similarities to related polypeptides found in other metazoan phyla. It is surprising that the genome of Porifera is large and comprises substantially more genes than Protostomia and Deuterostomia. On the basis of solid taxonomy and ecological data, the high value of this phylum for human application becomes obvious especially with regard to the field of chemical ecology and the hope to find novel potential drugs for clinical use. In addition, the benefit of efforts in understanding molecular biodiversity with focus on sponges can be seen in the fact that these animals as "living fossils" allow to stethoscope into the past of our globe especially with respect to the evolution of Metazoa.

Bauplan of Urmetazoa: Basis for Genetic Complexity of Metazoa

Sponges were first grouped to the animal-plants or plant-animals then to the Zoophyta or Mesozoa and finally to the Parazoa. Only after the application of molecular biological techniques was it possible to place the Porifera monophyletically with the other metazoan phyla, justifying a unification of all multicellular animals to only one kingdom, the Metazoa. The first strong support came from the discovery that cell-cell and cell-matrix adhesion molecules that were cloned from sponges and were subsequently expressed share a high DNA sequence and protein function similarity with the corresponding molecules of other metazoans. Besides these evolutionary novelties for Metazoa, sponges also have morphogens and transcription factors in common with other metazoan phyla. Surprisingly, even those elements exist in Porifera, which are characteristic for pattern and axis formation. Recent studies showed that epithelial layers of sponges are sealed against the extracellular milieu through tight-junction proteins. The cell culture system from sponges, the primmorphs, was suitable for understanding morphogenetic events. Finally, stem cell marker genes were isolated, which underscored that sponge cells have the capacity to differentiate. In the relatively short period of time, approximately 200 million years, the basic pathways had to be established that allowed the transition for multicellular organisms to a colonial system through the formation of adhesion molecules; based on the development of a complex immune system and the apoptotic machinery of an integrated system, the Urmetazoa, which evolved approximately 800 million years ago, could be reached. Hence, the Bauplan of the hypothetical Urmetazoa can now be constructed according to genomic regulatory systems similar to those found in higher Metazoa. These data caused a paradigmatic change; the Porifera are complex and simple but by far not primitive.

Biochemistry and cell biology of silica formation in sponges

The main inorganic material forming the skeletal elements in Demospongiae as well as in Hexactinellida, the spicules, is amorphous silica. The spicules occur in the cytoplasm and the extracellular space and also in the nucleus (as silicate crystals) of some sponge cells; the function in the latter compartment is unknown. Recent evidence shows that the formation of spicules is mediated by the enzyme silicatein. The cDNA as well as the gene encoding this enzyme was cloned from Suberites domuncula. The recombinant silicatein catalyzes the synthesis of amorphous silicate using tetraethoxysilane as substrate. The enzyme is dependent on ferric iron. Silicatein also has proteolytic (cathepsin-like) activity. Incubation of primmorphs, a special form of 3D-cell aggregates, with silicon resulted in a strong increase of their size from 1-7 mm to approximately 10 mm. The morphogenetic activity of silicate is underscored by the finding that this ion increases gene expression of silicatein and collagen. Based on these findings, it is concluded that both iron and silicate stimulate the activity of silicatein. Furthermore, it is proposed that the growing spicules are surrounded by the scavenger receptor which might be considered as a docking molecule for the collagen matrix into which the spicules are embedded.

Retinoid X receptor and retinoic acid response in the marine sponge Suberites domuncula

To date no nuclear receptors have been identified or cloned from the phylogenetically oldest metazoan phylum, the Porifera (sponges). We show that retinoic acid causes tissue regression in intact individuals of the demosponge Suberites domuncula and in primmorphs, special three-dimensional cell aggregates. Primmorphs were cultivated on a galectin/poly-L-lysine matrix in order to induce canal formation. In the presence of 1 or 50 micromol l(-1) retinoic acid these canals undergo regression, a process that is reversible. We also cloned the cDNA from S. domuncula encoding the retinoid X receptor (RXR), which displays the two motifs of nuclear hormone receptors, the ligand-binding and the DNA-binding domains, and performed phylogenetic analyses of this receptor. RXR expression undergoes strong upregulation in response to treatment with retinoic acid, whereas the expression of the sponge caspase is not increased. The gene encoding the LIM homeodomain protein was found to be strongly upregulated in response to retinoic acid treatment. These data indicate that the RXR and its ligand retinoic acid play a role in the control of morphogenetic events in sponges.

Origin of metazoan stem cell system in sponges: first approach to establish the model (Suberites domuncula)

It is established that Porifera (sponges) represent the earliest phylum which branched off from the common ancestor of all multicellular animals, the Urmetazoa. In the present study, the hypothesis is tested if, during this transition, pluripotent stem cells were formed which are provided-similar to the totipotent cells (archaeocytes/germ cells)-with a self-renewal capacity. As a model system, primmorphs from the sponge Suberites domuncula were used. These 3D-cell aggregates were cultivated in medium (RPMI 1640/seawater) either lacking silicate and ferric iron or in medium which was supplemented with these 'morphogenetic' factors. As molecular markers for the potential existence of stem cells in primmorphs, two genes which encode proteins found in stem cells of higher metazoan species, were cloned from S. domuncula. First, the noggin gene, which is present in the Spemann organizer of amphibians and whose translation product acts during the formation of dorsal mesoderm derivatives. The second gene encodes the mesenchymal stem cell-like protein. Both cDNAs were used to study their expression in primmorphs in dependence on the incubation conditions. It was found that noggin expression is strongly upregulated in primmorphs kept in the presence of silicate and ferric iron, while the expression of the mesenchymal stem cell-like protein was downregulated. These data are discussed with respect to the existence of stem cells in sponges.

Expression of one sponge Iroquois homeobox gene in primmorphs from Suberites domuncula during canal formation

Sponges (Porifera) represent the evolutionary oldest multicellular animals. They are provided with the basic molecules involved in cell-cell and cell-matrix interactions. We report here the isolation and characterization of a complementary DNA from the sponge Suberites domuncula coding for the sponge homeobox gene, SUBDOIRX-a. The deduced polypeptide with a predicted Mr of 44,375 possesses the highly conserved Iroquois-homeodomain. We applied in situ hybridization to localize Iroquois in the sponge. The expression of this gene is highest in cells adjacent to the canals of the sponge in the medulla region. To study the expression of Iroquois during development, the in vitro primmorph system from S. domuncula was used. During the formation of these three-dimensional aggregates composed of proliferating cells, the expression of Iroquois depends on ferric iron and water current. An increased expression in response to water current is paralleled with the formation of canal-like pores in the primmorphs. It is suggested that Iroquois expression is involved in the formation of the aquiferous system, the canals in sponges and the canal-like structures in primmorphs.

V-1, a protein expressed transiently during murine cerebellar development, regulates actin polymerization via interaction with capping protein

V-1 is a 12-kDa protein consisting of three consecutive ANK repeats, which are believed to serve as the surface for protein-protein interactions. It is thought to have a role in neural development for its temporal profile of expression during murine cerebellar development, but its precise role remains unknown. Here we applied the proteomic approach to search for protein targets that interact with V-1. The V-1 cDNA attached with a tandem affinity purification tag was expressed in the cultured 293T cells, and the protein complex formed within the cells were captured and characterized by mass spectrometry. We detected two polypeptides specifically associated with V-1, which were identified as the alpha and beta subunits of the capping protein (CP, alternatively called CapZ or beta-actinin). CP regulates actin polymerization by capping the barbed end of the actin filament. The V-1.CP complex was detected not only in cultured cells transfected with the V-1 cDNA but also endogenously in cells as well as in murine cerebellar extracts. An analysis of the V-1/CP interaction by surface plasmon resonance spectroscopy showed that V-1 formed a stable complex with the CP heterodimer with a dissociation constant of 1.2 x 10(-7) m and a molecular stoichiometry of approximately 1:1. In addition, V-1 inhibited the CP-regulated actin polymerization in vitro in a dose-dependent manner. Thus, our results suggest that V-1 is a novel component that regulates the dynamics of actin polymerization by interacting with CP and thereby participates in a variety of cellular processes such as actin-driven cell movements and motility during neuronal development.

Caspase-mediated apoptosis in sponges: cloning and function of the phylogenetic oldest apoptotic proteases from Metazoa

Sponges (phylum Porifera) represent the phylogenetically oldest metazoan phylum. These animals have complex cell adhesion and powerful immune systems which allow the formation of a distinct body plan. Consequently, an apoptotic machinery has to be predicted that allows sponges to eliminate unwanted cells accumulating during development. With the marine sponge Geodia cydonium, it is shown that allografts of these animals undergo apoptosis as demonstrated by apoptotic DNA fragmentation. Extracts from allografts contain an enzymic activity characteristic for caspases; as substrate to determine the cleavage activity, Ac-DEVD-AMC was applied. cDNAs encoding predicted caspase-3-related proteins were isolated; they comprise the characteristic structure known from caspases of other metazoan phyla. The two cDNAs are assumed to originate from one gene by alternative splicing; the longer form comprises a caspase recruitment domain (CARD), whereas the shorter one is missing CARD. The expression of sponge caspase genes is up-regulated during allograft rejection. In vivo incubation experiments with Ac-DEVD-CHO (a caspase-3 inhibitor) showed a reduction of apoptotic DNA fragmentation, whereas Ac-LEHD-CHO (an inhibitor of caspase-9) caused no effect. It is concluded, that for the establishment of the metazoan body plan, both the adhesion molecules and the apoptotic molecules (described here) were essential prerequisites.

Cultivation of primmorphs from the marine sponge Suberites domuncula: morphogenetic potential of silicon and iron

Marine demosponges (phylum Porifera) are rich sources for potent bioactive compounds. With the establishment of the primmorph system from sponges, especially from Suberites domuncula, the technology to cultivate sponge cells in vitro improved considerably. This progress was possible after the elucidation that sponges are provided with characteristic metazoan cell adhesion receptors and extracellular matrix molecules which allow their cells a positioning in a complex organization pattern. This review summarizes recent data on the cultivation of sponges in aquaria and--with main emphasis--of primmorphs in vitro. It is outlined that silicon and Fe(+++) contribute substantially to the formation of larger primmorphs (size of 10 mm) as well as of a canal system in primmorphs; canals are probably required for an improved oxygen and food supply. We conclude that the primmorph system will facilitate a sustainable use of sponges in the production of bioactive compounds; it may furthermore allow new and hitherto not feasible insights into basic questions on the origin of Metazoa.

Analysis of the sponge [Porifera] gene repertoire: implications for the evolution of the metazoan body plan

Sponges [phylum Porifera] form the basis of the metazoan kingdom and represent the evolutionary earliest phylum still extant. Hence, as living fossils, they are the taxon closest related to the hypothetical ancestor of all Metazoa, the Urmetazoa. Until recently, it was still unclear whether sponges are provided with a defined body plan. Only after the cloning, expression and functional studies of characteristic metazoan genes, could it be demonstrated that these animals comprise the structural elements which allow the sponge cells to organize themselves according to a body plan. Adhesion molecules involved in cell-cell and cell-matrix interactions have been identified. Among the cell-cell adhesion molecules the aggregation factor (AF) is the prominent particle. It is composed of a core protein that is associated with the adhesion molecules, a 36 kDa as well as a 86 kDa polypeptide. A galectin functions as a linker of the AF to the cell-membrane-associated receptor, the aggregation receptor (AR). The most important extracellular matrix molecules are collagen- and fibronectin-like molecules. These proteins interact with the cell-membrane receptors, the integrins. In addition, a neuronal receptor has been identified, which--together with the identified neuroactive molecules--indicate the existence of a primordial neuronal network already in Porifera. The primmorph system, aggregated cells that retain the capacity to proliferate and differentiate, has been used to demonstrate that a homeobox-containing gene, Iroquois, is expressed during canal formation in primmorphs. The formation of a body plan in sponges is supported by skeletal elements, the spicules, which are composed in Demospongiae as well as in Hexactinellida of amorphous, noncrystalline silica. In Demospongiae the spicule formation is under enzymic control of silicatein. Already at least one morphogen has been identified in sponges, myotrophin, which is likely to be involved in the axis formation. Taken together, these elements support the recent conclusions that sponges are not merely nonorganized cell aggregates, but already complex animals provided with a defined body plan.

Sustainable production of bioactive compounds from sponges: primmorphs as bioreactors

Sponges [phylum Porifera] are a rich source for the isolation of biologically active and pharmacologically valuable compounds with a high potential to become effective drugs for therapeutic use. However, until now, only one compound has been introduced into clinics because of the limited amounts of starting material available for extraction. To overcome this serious problem in line with the rules for a sustainable use of marine resources, the following routes can be pursued; first, chemical synthesis, second, cultivation of sponges in the sea (mariculture), third, growth of sponge specimens in a bioreactor, and fourth, cultivation of sponge cells in vitro in a bioreactor. The main efforts to follow the latter strategy have been undertaken with the marine sponge Suberites domuncula. This species produces compounds that affect neuronal cells, such as quinolinic acid, a well-known neurotoxin, and phospholipids. A sponge cell culture was established after finding that single sponge cells require cell-cell contact in order to retain their telomerase activity, one prerequisite for continuous cell proliferation. The sponge cell culture system, the primmorphs, comprises proliferating cells that have the potency to differentiate. While improving the medium it was found that, besides growth factors, certain ions (e.g. silicate and iron) are essential. In the presence of silicate several genes required for the formation of the extracellular matrix are expressed (silicatein, collagen and myotrophin). Fe3+ is essential for the synthesis of the spicules, and causes an increased expression of the ferritin-, septin- and scavenger receptor genes. Furthermore, high water current is required for growth and canal formation in the primmorphs. The primmorph system has already been successfully used for the production of pharmacologically useful, bioactive compounds, such as avarol or (2'-5')oligoadenylates. Future strategies to improve the sponge cell culture are discussed; these include the elucidation of those genes which control the proliferation phase and the morphogenesis phase, two developmental phases which the cells in primmorphs undergo. In addition, immortalization of sponge cells by transfection with genomic DNA appears to be a promising way, since recent studies underscore the applicability of this technique for sponges.

The hypothetical ancestral animal the Urmetazoa: Telomerase activity in sponges [Porifera]

Sponges (Porifera) represent the lowest metazoan phylum, characterized by a pronounced plasticity in the determination of cell lineages, and they are the closest related taxon to the hypothetical ancestral animal, the Urmetazoa, from which the metazoan lineages diverged. In a first approach to elucidate the molecular mechanisms controlling the switch from the cell lineage with a putative indefinite growth capacity to senescent, somatic cells, the activity of the telomerase as an indicator for immortality has been determined. The studies were performed with the marine demosponges Suberites domuncula and Geodia cydonium, in vivo with tissue but also in vitro using the primmorph system. Primmorphs are formed from dissociated cells which have retained their proliferation potency. It was found that the activity of telomerase in tissue of both sponges is high. Based on this and additional findings it is assumed that the separation of the senescent sponge cell lineage from the immortal germ-/somatic cell lineage is triggered by the loss of contact to cell adhesion factors. First evidence is included which suggests that the final progress of the senescent telomerase- negative cells to cell death is caused by apoptosis.

The Chemokine Networks in Sponges: Potential Roles in Morphogenesis, Immunity and Stem Cell Formation

Porifera (sponges) are now well accepted as the phylum which branched off first from the common ancestor of all metazoans, the Urmetazoa. The transition to the Metazoa became possible because during this phase, cell-cell as well as cell-matrix adhesion molecules evolved which allowed the formation of a colonial stage of animals. The next prerequisite for the evolution to the Urmetazoa was the establishment of an effective immune system which, flanked by apoptosis, allowed the formation of a first level of individuation. In sponges (with the model Suberites domuncula and Geodia cydonium), the main mediators of the immune responses are the chemokines. Since sponges lack a vascular system and consequently blood cells (in the narrow sense), we have used the term chemokines (in a broad sense) to highlight that the complex network of intercellular mediators initiates besides differentiation processes also cell movement. In the present review, the cDNAs encoding the following chemokines were described and the roles of their deduced proteins during self-self and nonself recognition outlined: the allograft inflammatory factor, the glutathione peroxidase, the endothelial-monocyte-activating polypeptide, the pre-B-cell colony-enhancing factor and the myotrophin as well as an enzyme, the (2-5)A synthetase, which is involved in cytokine response in vertebrates. A further step required to reach the evolutionary step of the integrated stage of the Urmetazoa was the acquisition of a stem cell system. In this review, first markers for stem cells (mesenchymal stem cell-like protein) as well as for chemokines involved in the maintenance of stem cells (noggin and glia maturation factor) are described at the molecular level, and a first functional analysis is approached. Taken together, it is outlined that the chemokine network was essential for the establishment of metazoans, which evolved approximately 600 to 800 million years ago.

Evolution of collagens

The extracellular matrix is often defined as the substance that gives multicellular organisms (from plants to vertebrates) their structural integrity, and is intimately involved in their development. Although the general functions of extracellular matrices are comparable, their compositions are quite distinct. One of the specific components of metazoan extracellular matrices is collagen, which is present in organisms ranging from sponges to humans. By comparing data obtained in diploblastic, protostomic, and deuterostomic animals, we have attempted to trace the evolution of collagens and collagen-like proteins. Moreover, the collagen story is closely involved with the emergence and evolution of metazoa. The collagen triple helix is one of numerous modules that arose during the metazoan radiation which permit the formation of large multimodular proteins. One of the advantages of this module is its involvement in oligomerization, in which it acts as a structural organizer that is not only relatively resistant to proteases but also permits the creation of multivalent supramolecular networks.

Iron induces proliferation and morphogenesis in primmorphs from the marine sponge Suberites domuncula

Dissociated cells from marine demosponges retain their proliferation capacity if they are allowed to form special aggregates, the primmorphs. On the basis of incorporation studies and septin gene expression, we show that Fe3+ ions are required for the proliferation of cells in primmorphs from Suberites domuncula. In parallel, Fe3+ induced the expression of ferritin and strongly stimulated the synthesis of spicules. This result is supported by the finding that the enzymatic activity of silicatein, converting organosilicon to silicic acid, depends on Fe3+. Moreover, the expression of a scavenger receptor molecule, possibly involved in the morphology of spicules, depends on the presence of Fe3+. We conclude that iron is an essential factor in proliferative and morphogenetic processes in primmorphs.

Sponge Bcl-2 homologous protein (BHP2-GC) confers distinct stress resistance to human HEK-293 cells

It is established that sponges, the phylogenetically oldest still extant phylum of Metazoa, possess key molecules of the apoptotic pathways, that is members from the Bcl-2 family and a pro-apoptotic molecule with death domains. Here we report on transfection studies of human cells with a sponge gene, GCBHP2. Sponge tissue was exposed to heat shock and tributyltin, which caused an upregulation of gene expression of GCBHP2. The cDNA GCBHP2 was introduced into human HEK-293 cells and mouse NIH-3T3 cells; the stable transfection was confirmed by the identification of the transcripts, by Western blotting as well as by immunofluorescence using antibodies raised against the recombinant polypeptide. HEK-293 cells, transfected with GCBHP2, showed high resistance to serum starvation and tributyltin treatment, compared to mock-transfected cells. In contrast to mock-transfected cells, GCBHP2-transfected cells activated caspase-3 to a lower extent. Thus, sponges contain gene(s) involved in apoptotic pathway(s) displaying their function also in human cells.

Suppression of allograft rejection in the sponge Suberites domuncula by FK506 and expression of genes encoding FK506-binding proteins in allografts

Porifera (sponges) are, evolutionarily, the oldest metazoan phylum. Recent molecular data suggest that these animals possess molecules similar to and homologous with those of the innate and adaptive immune systems of higher Metazoa. Applying the biological system of parabiosis and the technique of differential display of mRNA, two cDNAs encoding putative FK506-binding proteins were isolated. FK506 is successfully used in clinics as a drug to prevent allograft rejection and is toxic to Suberites domuncula cells in vitro at doses above 100ng ml−1. Autograft fusion of transplants from S. domuncula was not affected by FK506. Allograft non-fusion was not affected by FK506 at toxic doses; however, at the non-toxic dose of 20ng ml−1, the allografts fused with each other. It is shown that at the attachment zone in untreated and (particularly drastic) in FK506-treated allografts, expression of the genes encoding the FK506-binding proteins is upregulated. These data indicate that the drug FK506 suppresses allograft rejection in S. domuncula, most probably via interaction with expression of the gene coding for the FK506-binding proteins.

Review: How was metazoan threshold crossed? The hypothetical Urmetazoa

The origin of Metazoa remained--until recently--the most enigmatic of all phylogenetic problems. Sponges [Porifera] as "living fossils", positioned at the base of multicellular animals, have been used to answer basic questions in metazoan evolution by molecular biological techniques. During the last few years, cDNAs/genes coding for informative proteins have been isolated and characterized from sponges, especially from the marine demosponges Suberites domuncula and Geodia cydonium. The analyses of their deduced amino acid sequences allowed a molecular biological resolution of the monophyly of Metazoa. Molecules of the extracellular matrix/basal lamina, with the integrin receptor, fibronectin and galectin as prominent examples, cell-surface receptors (tyrosine kinase receptors), elements of nerve system/sensory cells (metabotropic glutamate receptor), homologs/modules of an immune system [immunoglobulin-like molecules, SRCR- and SCR-repeats, cytokines, (2-5)A synthetase], as well as morphogens (myotrophin) classify the Porifera as true Metazoa. As "living fossils", provided with simple, primordial molecules allowing cell-cell and cell-matrix adhesion, as well as processes of signal transduction as known in a more complex manner from higher Metazoa, sponges also show peculiarities. Tissues of sponges are rich in telomerase activity, suggesting a high plasticity in the determination of cell lineages. It is concluded that molecular biological studies with sponges as models will not only help to understand the evolution to the Metazoa but also the complex, hierarchical regulatory network of cells in higher Metazoa [reviewed in Progress in Molecular Subcellular Biology, vols. 19, 21 (1998) Springer Verlag]. The hypothetical ancestral animal, the Urmetazoa, from which the metazoan lineages diverged (more than 600 MYA), may have had the following characteristics: cell adhesion molecules with intracellular signal transduction pathways, morphogens/growth factors forming gradients, a functional immune system, and a primordial nerve cell/receptor system.

Expression of silicatein and collagen genes in the marine sponge Suberites domuncula is controlled by silicate and myotrophin

The major skeletal elements in the (Porifera) sponges, are spicules formed from inorganic material. The spicules in the Demospongiae class are composed of hydrated, amorphous silica. Recently an enzyme, silicatein, which polymerizes alkoxide substrates to silica was described from the sponge Tethya aurantia. In the present study the cDNA encoding silicatein was isolated from the sponge Suberites domuncula. The deduced polypeptide comprises 331 amino acids and has a calculated size of Mr 36 306. This cDNA was used as a probe to study the potential role of silicate on the expression of the silicatein gene. For these studies, primmorphs, a special form of aggregates composed of proliferating cells, have been used. It was found that after increasing the concentration of soluble silicate in the seawater medium from around 1 microM to approximately 60 microM, this gene is strongly upregulated. Without additional silicate only a very weak expression could be measured. Because silica as well as collagen are required for the formation of spicules, the expression of the gene encoding collagen was measured in parallel. It was also found that the level of transcripts for collagen strongly increases in the presence of 60 microM soluble silicate. In addition, it is demonstrated that the expression of collagen is also upregulated in those primmorphs which were treated with recombinant myotrophin obtained from the same sponge. Myotrophin, however, had no effect on the expression of silicatein. From these data we conclude that silicate influences the expression of the enzyme silicatein and also the expression of collagen, (via the mediator myotrophin).