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PubMed2005

Use of hydra for chronic toxicity assessment of waters intended for human consumption.

Methods developed with the cnidarian, Hydra attenuata (Pallas), have proven effective for screening acute toxicity in aqueous samples, whereas their use in revealing (sub)chronic toxic effects have had mitigated success. We therefore sought to explore manifestations of hydra mortality and abnormal morphological changes, as well as the reproductive capacity of hydras to further enhance the bioassay sensitivity and to assess (sub)chronic toxicity. These parameters were recorded following the onset of experiments after 8, 12 and 19-21 days of hydra exposure. Results obtained with potable waters (30 brands of bottled waters and artesian waters from 9 wells) showed chronic sublethal and lethal effects or reproduction rate inhibition for most samples. The effectiveness of the hydra toxicity test was demonstrated in comparison with other widely used bioassays. Our previous and present investigations suggest that hydra is a reliable and relevant test organism for the assessment of acute and chronic water toxicity.

Animals↗
PubMed2005

Control of foot differentiation in Hydra: phylogenetic footprinting indicates interaction of head, bud and foot patterning systems.

Homeodomain transcription factor CnNK-2 seems to play a major role in foot formation in Hydra. Recently, we reported in vitro evidence indicating that CnNK-2 has autoregulatory features and regulates expression of the morphogenetic peptide pedibin. We proposed that CnNK-2 and pedibin synergistically orchestrate foot differentiation processes. Here, we further analyzed the regulatory network controlling foot formation in Hydra. By phylogenetic footprinting we compared the CnNK-2 5'-flanking sequence from two closely related species, Hydra vulgaris and Hydra oligactis. Unexpectedly, we detected a highly conserved binding site for HNF-3beta, a vertebrate Forkhead transcription factor, in the CnNK-2 5'-flanking region. The Hydra HNF-3beta homolog budhead is predominantly expressed in the apical region of the body column and early during budding. Budhead is absent from tissue expressing CnNK-2 and thought to be involved in determining tissue for head differentiation. By electrophoretic mobility shift assays we demonstrate an in vitro interaction between recombinant budhead protein and the interspecific conserved HNF-3beta binding motif in the CnNK-2 5'-flanking region. Our results strengthen the view of CnNK-2 as an important regulator during foot patterning processes. Furtheron, they point to budhead as a candidate for a transcriptional regulator of CnNK-2 and to an interaction of foot and head patterning processes in Hydra on the molecular level.

Animals↗
PubMed2005

Toxic polypeptides of the hydra--a bioinformatic approach to cnidarian allomones.

Cnidarians such as hydrae and sea anemones are sessile, predatory, soft bodied animals which depend on offensive and defensive allomones for prey capture and survival. These allomones are distributed throughout the entire organism both in specialized stinging cells (nematocytes) and in the body tissues. The cnidarian allomonal system is composed of neurotoxins, cytolysins and toxic phospholipapses. The present bioinformatic survey was motivated by the fact that while hydrae are the most studied model cnidarian, little is known about their allomones. A large-scale EST database from Hydra magnipapillata was searched for orthologs of known cnidarian allomones, as well as for allomones found in other venomous organisms. We show that the hydrae express orthologs of cnidarian phospholipase A2 toxins and cytolysins belonging to the actinoporin family, but could not find orthologs of the 'classic' short chain neurotoxins affecting sodium and potassium conductance. Hydrae also express proteins similar to elapid-like phospholipases, CRISP proteins, Prokineticin-like polypeptides and toxic deoxyribonucleases. Our results illustrate a high level of complexity in the hydra allomonal system, suggest that several toxins represent a basal component of all cnidarian allomones, and raise the intriguing possibility that similar proteins may fulfill both endogenous and allomonal roles in cnidaria.

Amino Acid Sequence↗
PubMed1998

Modulation of gamma-aminobutyric acid (GABA) receptors and the feeding response by neurosteroids in Hydra vulgaris.

Gamma-Aminobutyric acid (GABA) receptors are present in membrane preparations from Hydra vulgaris, one of the most primitive organisms with a nervous system. These receptors are sensitive to muscimol and benzodiazepines and appear to be important in the regulation of the feeding response. The effects of neurosteroids, general anaesthetics, and GABA antagonists on GABA(A) receptors in membranes prepared from Hydra and on the feeding response have now been investigated. The neurosteroids tetrahydroprogesterone and tetrahydrodeoxycorticosterone increased [3H]GABA binding to hydra membranes with nanomolar potency (EC50, 141+/-11 and 623+/-36 nM, respectively) and high efficacy (maximal increase 79+/-6.5 and 62+/-4%, respectively), whereas the 3beta-hydroxy epimer of tetrahydroprogesterone was ineffective. The benzodiazepine receptor ligands diazepam (100 microM), clonazepam (100 microM) and abecarnil (30 microM) enhanced [3H]GABA binding to Hydra membranes by 22, 20 and 24%, respectively; effects abolished by the specific benzodiazepine antagonist flumazenil (100 microM). On the contrary, the peripheral benzodiazepine receptor ligand 4'chlorodiazepam failed to affect [3H]GABA binding to Hydra membranes. The general anaesthetics propofol and alphaxalone similarly increased (+38% and +30% respectively) [3H]GABA binding. Moreover, [3H]GABA binding to Hydra membranes was completely inhibited by the GABA(A) receptor antagonist SR 95531, whereas bicuculline was without effect. The modulation of GABA(A) receptors in vitro by these various drugs correlated with their effects on the glutathione-induced feeding response in the living animals. Tetrahydroprogesterone and tetrahydrodeoxy-corticosterone (1 to 10 microM) prolonged, in a dose-dependent manner, the duration of mouth opening induced by 10 microM glutathione, with maximal effects of +33 and +29%, respectively, apparent at 10 microM neurosteroid. Alphaxalone (10 microM) similarly increased (+33%) the effect of glutathione. The effects of steroids on the feeding response were inhibited by SR 95531 in a dose-dependent manner; t-butylbyclophosphorothyonate (1 microM), a specific Cl- channel blocker, which per se, like picrotoxin but not bicuculline, shortened the duration of the response, also counteracted the steroids effects at 1 microM. These results suggest that the modulation of GABA(A) receptors by steroids is an ancient characteristic of the animal kingdom and that the pharmacological properties of these receptors have been highly conserved through evolution.

Anesthetics↗
PubMed1998

Mortality patterns suggest lack of senescence in hydra.

Senescence, a deteriorative process that increases the probability of death of an organism with increasing chronological age, has been found in all metazoans where careful studies have been carried out. There has been much controversy, however, about the potential immortality of hydra, a solitary freshwater member of the phylum Cnidaria, one of the earliest diverging metazoan groups. Researchers have suggested that hydra is capable of escaping aging by constantly renewing the tissues of its body. But no data have been published to support this assertion. To test for the presence or absence of aging in hydra, mortality and reproductive rates for three hydra cohorts have been analyzed for a period of four years. The results provide no evidence for aging in hydra: mortality rates have remained extremely low and there are no apparent signs of decline in reproductive rates. Hydra may have indeed escaped senescence and may be potentially immortal.

Aging↗
PubMed1992

Conservation of the prohormone convertase gene family in metazoa: analysis of cDNAs encoding a PC3-like protein from hydra.

A subclass of proteolytic enzymes that correctly cleave precursor proteins at paired basic residues and are structurally related to the bacterial subtilisins has recently been identified. In yeast, a single membrane-bound proteolytic processing enzyme encoded by the kex2 gene has been found, whereas in higher vertebrates cDNAs encoding four distinct enzymes (PC2, PC3, furin, and PACE 4) have been identified. Like kex2, furin (also known as PACE) contains a hydrophobic transmembrane domain, but PC2, PC3, and PACE 4 lack this feature. All five enzymes exhibit striking similarities in their catalytic domains, and this suggests that they have arisen from a common ancestral subtilisin-like gene. We report here the identification of cDNAs encoding a protein that is similar in structure to PC3 from a simple metazoan, Hydra vulgaris (formerly Hydra attenuata). cDNAs encoding two isoforms of this PC3-like enzyme were obtained that differ only in their carboxyl-terminal sequences, probably due to alternative splicing of a common pre-mRNA. Neither form contains a transmembrane domain. Predicted amino acid sequence comparisons revealed that the hydra PC3-like enzyme is 55.4% and 56.7% identical in the catalytic domain to mouse PC3 and human furin, respectively. RNA blot analyses revealed that the PC3-like RNA is expressed predominantly in the hydra body column and not in the head region, although the hydra head contains a high density of nerve cells, which synthesize a variety of neuropeptides. For this reason, we suspect that another proprotein cleavage enzyme isoform may be expressed in head nerve cells. The isolation of a PC3-like cDNA from hydra is consistent with the presence of neuroendocrine cells and indicates that the PC/furin gene family has been well conserved in all metazoa. A simplified nomenclature for the group of mammalian processing proteases is proposed.

Amino Acid Sequence↗
PubMed1997

Systematic isolation of peptide signal molecules regulating development in hydra: LWamide and PW families.

To isolate new peptide signal molecules involved in regulating developmental processes in hydra, a novel screening project was developed. Peptides extracted from the tissue of Hydra magnipapillata were systematically purified to homogeneity using HPLC. A fraction of each purified peptide was examined by differential display-PCR for its ability to affect gene expression in hydra. Another fraction was used to determine the tentative structure using an amino acid sequence analyzer and/or a mass spectrometer. Based on the results, peptides of potential interest were selected for chemical synthesis, followed by confirmation of the identity of the synthetic with the native peptides using HPLC. Using this approach, 286 peptides have been isolated, tentative amino acid sequences have been determined for 95 of them, and 19 synthetic peptides identical to native ones were produced. The 19 synthetic peptides were active in a variety of biological tests. For example, Hym-54 stimulated muscle contraction in adult polyps of hydra and sea anemone, Anthopleura fuscoviridis, and induced metamorphosis of planula, the larval stage, into polyps in a marine hydrozoan species, Hydractinia serrata. Another peptide, Hym-33H, inhibited nerve cell differentiation in hydra and induced tissue contraction in planula of Hydractinia serrata. The evidence obtained so far suggests that hydra contains a large number (>350) of peptide signal molecules involved in regulating developmental or other processes in cnidaria. These peptides can be isolated and their functions examined systematically with the new approach developed in this study.

Amino Acid Sequence↗
PubMed2000

Characterization of hydra type IV collagen. Type IV collagen is essential for head regeneration and its expression is up-regulated upon exposure to glucose.

Hydra vulgaris mesoglea is a primitive basement membrane that also exhibits some features of an interstitial matrix. We have characterized cDNAs that encode the full-length hydra alpha1(IV) chain. The 5169-base pair transcript encodes a protein of 1723 amino acids, including an interrupted 1455-residue collagenous domain and a 228-residue C-terminal noncollagenous domain. N-terminal sequence analyses of collagen IV peptides suggest the molecule is homotrimeric. Denatured hydra type IV collagen protein occurs as dimers and higher order aggregates held together by nonreducible cross-links. Hydra collagen IV exhibits no functional evidence for the presence of a 7 S domain. Type IV collagen is expressed by the ectoderm along the entire longitudinal axis of the animal but is most intense at the base of the tentacles at the site of battery cell transdifferentiation. Antisense studies show that inhibition of collagen IV translation causes a blockage in head regeneration, indicating its importance in normal hydra development. Exposure of adult hydra to 15 mm glucose resulted in up-regulation of type IV collagen mRNA levels within 48 h and significant thickening of the mesoglea within 14 days, suggesting that basement membrane thickening seen in diabetes may be, in evolutionary terms, an ancient glucose-mediated response.

Amino Acid Sequence↗
PubMed2004

Unique catabolic pathway of glycosphingolipids in a hydrozoan, Hydra magnipapillata, involving endoglycoceramidase.

Endoglycoceramidase (EGCase; EC 3.2.1.123) is an enzyme capable of cleaving the glycosidic linkage between oligosaccharides and ceramides of various glycosphingolipids. We detected strong EGCase activity in animals belonging to Cnidaria, Mollusca, and Annelida and cloned the enzyme from a hydra, Hydra magnipapillata. The hydra EGCase, consisting of 517 amino acid residues, showed 19.2% and 50.2% identity to the Rhodcoccus and jellyfish EGCases, respectively. The recombinant hydra enzyme, expressed in CHOP (Chinese hamster ovary cells expressing polyoma LT antigen) cells, hydrolyzed [14C]GM1a to produce [14C]ceramide with a pH optimum at 3.0-3.5. Whole mount in situ hybridization and immunocytochemical analysis revealed that EGCase was widely expressed in the endodermal layer, especially in digestive cells. GM1a injected into the gastric cavity was incorporated and then directly catabolized by EGCase to produce GM1a-oligosaccharide and ceramide, which were further degraded by exoglycosidases and ceramidase, respectively. However, hydra exoglycosidases did not hydrolyze GM1a directly. These results indicate that the EGCase is indispensable for the catabolic processing of dietary glycosphingolipids in hydra, demonstrating the unique catabolic pathway for glyosphingolipids in the animal.

Amino Acid Sequence↗
PubMed1997

Hydra regeneration from recombined ectodermal and endodermal tissue. II. Differential stability in the ectodermal and endodermal epithelial organization.

Hydra tissue consists of the ectodermal and the endodermal layers. When the two layers were separated by procaine treatment and then recombined, the ectodermal epithelial cells spread as a single cell layer over the endoderm as in epiboly in vertebrate embryogenesis, and the resultant spherical structure subsequently regenerated into a complete hydra. In this study, light and electron microscopy were used to examine the structural changes which took place in the cells and tissue during this epibolic ectodermal spreading process. Within a few hours after tissue recombination, the endoderm underwent dramatic changes; it lost its epithelial sheet organization, and turned into a mass of irregularly shaped cells without the apical-basal cell polarity initially present. In contrast, the ectoderm maintained its basic epithelial sheet organization as it spread over the endoderm. Later, the endodermal epithelial cells reorganized themselves into a single-layered epithelial sheet underneath the spreading ectodermal layer. The resultant spherical structure consisted of a single layer of ectodermal epithelial cells outside, a single layer of endodermal epithelial cells inside, and an empty cavity in the center as in normal hydra tissue. This structure regenerated into hydra in the following days. These and other observations demonstrate that the two-layered epithelial sheet organization is highly dynamic, and that its stability is maintained by strong interactions between the two layers in normal hydra. It is suggested that this dynamic nature of the hydra tissue, particularly the high plasticity of the endodermal epithelial sheet organization, may be an important element for the high regenerative capacity of this organism.

Animals↗
PubMed1978

Genetic analysis of developmental mechanisms in Hydra. IV. Characterization of a nematocyst-deficient strain.

The authors have previously found that mutant hydra strains showing various types of developmental defects can be isolated through sexual inbreeding of wild hydra. One such defective strain, called nem-4, contains virtually no stenoteles, one of the four types of nematocysts present in hydra, in its tentacles. However, stenoteles are present at a normal level in the body column of this strain, and they are turned over also at a normal rate. Grafting experiments between the head region of nem-4 hydra and the body column of wild type hydra (and vice versa) showed that wild type stenotele nematocytes can move into nem-4 tentacles but that nem-4 stenotele nematocytes can not move into the wild type tentacles. These observations suggest that the stenotele nematocytes are produced normally by differentiation from the interstitial cells in the body column of nem-4 hydra, but that they are somehow prevented from migrating into the tentacles in this strain.

Animals↗
PubMed1994

Evidence for cell surface extracellular matrix binding proteins in Hydra vulgaris.

The present study was designed to identify and functionally characterize potential cell surface extracellular matrix binding proteins in Hydra vulgaris. Using [3H]-laminin as a probe, radioreceptor analysis of a dissociated mixed hydra cell preparation indicated that the average number of laminin binding sites per cell was about 10,000 with a dissociation constant of 1.49 nM. These binding sites could be displaced with unlabelled laminin in a dose-dependent manner and with high concentrations (500 nM) of unlabelled fibronectin. No displacement with type-IV collagen and type-I collagen was observed. Immunoscreening studies with a battery of antibodies raised to mammalian extracellular matrix (ECM) binding proteins indicated potential cell surface binding sites for the anti-beta 1 integrin monoclonal antibody, mAb JG22. Cell adhesion studies indicated that mAb JG22 blocked binding of hydra cells to laminin, but did not affect their binding to fibronectin, type-IV collagen, or type-I collagen. Light and electron microscopic immunocytochemical studies indicated that mAb JG22 localized to the basal plasma membrane of ectodermal and endodermal epithelial cells. Immunoprecipitation studies identified tow major bands with masses of about 196 kDa and 150 kDa under reducing conditions, and two bands with masses of > 200 kDa under non-reducing conditions. Functional studies indicated that mAb JG22 could reversibly block morphogenesis of hydra cell aggregates, and could block in vivo interstitial cell migration in hydra grafts. These observations indicate that hydra has cell surface binding sites for ECM components which are functionally important during development of this simple Cnidarian.

Animals↗
PubMed1992

Molecular cloning and characterization of Na,K-ATPase from Hydra vulgaris: implications for enzyme evolution and ouabain sensitivity.

We have used molecular and biochemical techniques to analyze Na,K-ATPase from a simple metazoan, Hydra vulgaris. First we isolated and characterized cDNA clones encoding the Na,K-ATPase alpha subunit from a Hydra lambda gt11 cDNA library. The open reading frame predicts a protein of 1031 amino acids that bears a high degree of primary sequence and secondary structure similarity to mammalian, avian, and arthropod alpha subunits. The predicted Hydra alpha subunit contains charged residues at the termini of the H1-H2 extracellular domain, suggesting that the Hydra alpha subunit may be resistant to cardiac glycoside inhibition. Biochemical analysis of partially purified Hydra Na,K-ATPase reveals both high- and low-affinity components of ouabain-inhibitable ATPase activity. Our results suggest that the evolutionary ancestor of all metazoans possessed a Na,K-ATPase alpha subunit that was highly conserved with respect to its vertebrate counterparts. Further, expression of a ouabain-resistant Na,K-ATPase activity in Hydra suggests that cardiac glycoside resistance arose randomly during evolution of the Na,K-ATPase.

Amino Acid Sequence↗
PubMed1975

Positional information and pattern regulation in hydra: enzyme profiles.

Certain key enzymes of alternative pathways of glucose metabolism, of amino acid metabolism and of redox systems have been measured in hydra and this profile compared with mammalian differentiated tissues with a view to locating pathways of specific importance in hydra. There was a marked constant proportionality in the major part of the enzymes investigated, the profile suggested a metabolic pattern geared to utilization of amino acids as a carbon source for biosynthesis and energy production and to the production and conservation of pyruvate. The importance of conversion to ionized forms was noted. The most notable specific proportion changes were the exceptionally low lactate dehydrogenase, malic enzyme and the relatively high citrate synthase. The proximal-distal gradients in hydra were examined and these gradients suggested a switch to a more anaerobic type of metabolism and an elevation of the pentose phosphate pathway as the basal region was approached. Measurements of the formation of 14CO2 from specifically labelled glucose provided additional evidence for the functional activity and polarity of the pentose phosphate pathway in hydra. The effect of oligomycin, which can reverse polarity in hydra, had a significant effect on gradients of enzymes eliminating all except that observed for G6P dehydrogenase. The profile suggested a movement towards a more anaerobic type of metabolism, in keeping with the known biochemical action of this inhibitor. It is suggested that redox states and/or phosphorylation states may be featured in the positional information of cells in hydra.

Alanine Transaminase↗
PubMed1995

Competition for factors and cellular resources as a principle of pattern formation in Hydra. I. Increase of the potentials for head and bud formation and rescue of the regeneration-deficient mutant reg-16 by treatment with diacylglycerol and arachidonic acid.

The mutant strain reg-16 of Hydra magnipapillata has less capacity to regenerate a head than the wild-type strain 105 when examined in a standard test. The present comparative study with various strains of Hydra shows: (1) The head-forming potential of reg-16 and also of a widely used strain of Hydra vulgaris is severely impaired by the presence of a just-emerging or latent bud. (2) Periodic treatment with dioctanoylglycerol (DAG), a known activator of protein kinase C (PKC), plus arachidonic acid (AA), the mother compound of the eicosanoid signal substances, enabled reg-16 and H. vulgaris to insert additional tentacles into their original whorl while the export of cells by budding was reduced. (3) On the other hand, during the period of daily treatment with DAG+AA, potentials for head and bud formation were stored. Gastric segments excised from pretreated animals formed more tentacles than untreated wild-type 105 and even formed supernumerary head structures; in addition, segments excised from all body regions quickly resumed budding in spite of starvation and while they regenerated a head. (4) With continued treatment supernumerary tentacles were elicited in all strains although with high frequency only in Hydra magnipapillata, wt105. However, while wt105 formed supernumerary head structures preferentially at ectopic sites, reg-16, H. vulgaris, and Hydra oligactis instead increased the number of tentacles in the apical head, which occasionally split into two heads. (5) The treatment with DAG+AA caused the budding zone to shift closer to the foot end. (6) In H. vulgaris a pulse treatment with a high dose of DAG frequently caused a mirror image duplication of the budding zone; in wt105 mere excessive feeding over 2-3 weeks may have the same effect. The hypothesis is proposed that a regenerating head and a beginning bud compete for hormone-like factors, which enable the cells to increase positional value, and for precursor cells. Periodic treatment with activators of PKC plus AA leads to an augmentation of these resources, and head structures and buds can be produced simultaneously. Traditional terms are reinterpreted correspondingly: the high level of "head inhibition" in reg-16 is interpreted as a low level of resources, in particular, of head-promoting factors, and the low head activation level as a low ability to make use of resources.

Animals↗
PubMed2002

Cloning and characterisation of PKB and PRK homologs from Hydra and the evolution of the protein kinase family.

Two new serine/threonine protein kinases have been cloned from Hydra cDNA. The first of these kinases belongs to the PKB/Akt family. It is expressed ubiquitously in Hydra at a relatively low level but is upregulated during head regeneration. The second kinase is a member of the PRK/PKN family. It is ubiquitously expressed in Hydra tissue, albeit at a higher level than PKB. Construction of a phylogenetic tree including the Hydra PRK and PKB kinases and two PKC homologs previously cloned by Hassel and comparing them with members of the PKC, PKB and PRK families from porifera, Dictyostelium,yeast, Drosophila, Caenorhabditis and humans provide support for a simple model for the evolution of these kinase families. An ancestral precursor which contained a pleckstrin homology domain in its N-terminus and a C-terminal kinase domain gave rise to PKB in Dictyostelium. From this ancestor the PKB/PRK and PKC families evolved. The pleckstrin homology domain was lost in the PKC and PRK families and kept in the PKB family. PKB homologs have now been found in a variety of multicellular animals with Hydra being the phylogenetically earliest representative. Members of the PRK/PKC family, on the other hand, are also present in fungi. The precursor for these kinases must have contained N-terminal regulatory domains that were retained in fungal PRKs but subsequently partitioned between kinases of the PKC and PRK groups in metazoans.

Amino Acid Sequence↗
PubMed2000

Molecular and biological characterization of a zonula occludens-1 homologue in Hydra vulgaris, named HZO-1.

Zonula occludens-1 (ZO-1) is one of the earliest identified molecular components of tight junctions. Sequence analysis has placed ZO-1 into the broader membrane-associated guanylate kinase (MAGUK) protein family that contains such diverse members as post-synaptic density 95 (PSD-95), Drosophila discs large tumor suppressor gene product (dlg-A), p55, and TamA. Studies in both vertebrates and invertebrates have established that the MAGUK family is involved in a wide variety of cellular functions. These functions involve the regulation of such cellular processes as: (1) tight junction formation, (2) cell proliferation, (3) cell differentiation, and (4) neuronal synapse transmission. Extending these studies, we report the presence of a ZO-1 homologue in Hydra vulgaris, a member of the Cnidaria, the second oldest phylum of the animal kingdom. Hydra ZO-1 (HZO-1) is encoded by a single messenger RNA (mRNA) of approximately 6.0 kb that contains an open reading frame of 5,085 bp. The 191 kDa predicted protein consists of a characteristic MAGUK domain structure, including three PSD-95/SAP90, discs-large, ZO-1 (PDZ) domains, a src homology (SH3) domain, and a guanylate kinase (GUK) domain. Western blot analysis using an antibody generated from a synthetic peptide designed from the HZO-1 sequence confirmed the presence of a Hydra protein of the appropriate mass. While whole mount in situ hybridization determined that HZO-1 mRNA was expressed along the entire longitudinal axis of Hydra, cross-sectional analysis established that HZO-1 mRNA expression was restricted to the ectoderm or outer cell layer of the organism's epithelial bilayer. Consistent with this mRNA expression pattern, immunofluorescence studies localized HZO-1 protein to the apical plasma membrane of ectodermal cells. It is unclear what role HZ0-1 has in the cellular physiology of Hydra; however, immunolocalization studies indicate a conserved plasma membrane-associated function(s), as reported for its counterparts in other invertebrate and vertebrate species. These studies establish that the MAGUK family of proteins with a membrane-associated function arose early during metazoan evolution, even before the divergence of protostomes and deuterostomes.

Amino Acid Sequence↗
PubMed1977

Isolation of a substance activating foot formation in hydra.

We have developed an assay for a substance from hydra that accelerates foot regeneration in the animal. This substance is specific for the foot as evidenced by the following findings: (1) It is present in the animal as a steep gradient descending from foot to head, paralleling the foot-forming potential of the tissue (2) It does not accelerate head regeneration, nor do the head factors of hydra discovered by Schaller (1973) and Berking (1977) accelerate foot regeneration. We propose that the foot-activating substance is a morphogen responsible for foot formation in hydra. The foot activator can be extracted from hydra tissue with methanol and separated from other known morphogens of hydra by gel filtration and ion-exchange chromatography. A substance with similar biological and physicochemical properties can be isolated from sea anemones.

Animals↗