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Uri Frank - One of the best experts on this subject based on the ideXlab platform.
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The colonial cnidarian Hydractinia
EvoDevo, 2020Co-Authors: Uri Frank, Matthew L Nicotra, Christine E. SchnitzlerAbstract:Hydractinia , a genus of colonial marine cnidarians, has been used as a model organism for developmental biology and comparative immunology for over a century. It was this animal where stem cells and germ cells were first studied. However, protocols for efficient genetic engineering have only recently been established by a small but interactive community of researchers. The animal grows well in the lab, spawns daily, and its relatively short life cycle allows genetic studies. The availability of genomic tools and resources opens further opportunities for research using this animal. Its accessibility to experimental manipulation, growth- and cellular-plasticity, regenerative ability, and resistance to aging and cancer place Hydractinia as an emerging model for research in many biological and environmental disciplines.
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CRISPR/Cas9-mediated gene knockin in the hydroid Hydractinia symbiolongicarpus
BMC Genomics, 2018Co-Authors: Steven M. Sanders, Uri Frank, Christine E. Schnitzler, Hakima Flici, Zhiwei Ma, Julia M. Hughes, Brooke M. Riscoe, Gregory A. Gibson, Alan M. Watson, Andreas D. BaxevanisAbstract:Background Hydractinia symbiolongicarpus, a colonial cnidarian, is a tractable model system for many cnidarian-specific and general biological questions. Until recently, tests of gene function in Hydractinia have relied on laborious forward genetic approaches, randomly integrated transgenes, or transient knockdown of mRNAs. Results Here, we report the use of CRISPR/Cas9 genome editing to generate targeted genomic insertions in H. symbiolonigcarpus . We used CRISPR/Cas9 to promote homologous recombination of two fluorescent reporters, eGFP and tdTomato, into the Eukaryotic elongation factor 1 alpha ( Eef1a ) locus. We demonstrate that the transgenes are expressed ubiquitously and are stable over two generations of breeding. We further demonstrate that CRISPR/Cas9 genome editing can be used to mark endogenous proteins with FLAG or StrepII-FLAG affinity tags to enable in vivo and ex vivo protein studies. Conclusions This is the first account of CRISPR/Cas9 mediated knockins in Hydractinia and the first example of the germline transmission of a CRISPR/Cas9 inserted transgene in a cnidarian . The ability to precisely insert exogenous DNA into the Hydractinia genome will enable sophisticated genetic studies and further development of functional genomics tools in this understudied cnidarian model.
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CRISPR/Cas9-mediated gene knockin in the hydroid Hydractinia symbiolongicarpus
BMC genomics, 2018Co-Authors: Steven M. Sanders, Uri Frank, Christine E. Schnitzler, Hakima Flici, Brooke M. Riscoe, Gregory A. Gibson, Alan M. Watson, Julia Hughes, Andreas D. BaxevanisAbstract:Hydractinia symbiolongicarpus, a colonial cnidarian, is a tractable model system for many cnidarian-specific and general biological questions. Until recently, tests of gene function in Hydractinia have relied on laborious forward genetic approaches, randomly integrated transgenes, or transient knockdown of mRNAs. Here, we report the use of CRISPR/Cas9 genome editing to generate targeted genomic insertions in H. symbiolonigcarpus. We used CRISPR/Cas9 to promote homologous recombination of two fluorescent reporters, eGFP and tdTomato, into the Eukaryotic elongation factor 1 alpha (Eef1a) locus. We demonstrate that the transgenes are expressed ubiquitously and are stable over two generations of breeding. We further demonstrate that CRISPR/Cas9 genome editing can be used to mark endogenous proteins with FLAG or StrepII-FLAG affinity tags to enable in vivo and ex vivo protein studies. This is the first account of CRISPR/Cas9 mediated knockins in Hydractinia and the first example of the germline transmission of a CRISPR/Cas9 inserted transgene in a cnidarian. The ability to precisely insert exogenous DNA into the Hydractinia genome will enable sophisticated genetic studies and further development of functional genomics tools in this understudied cnidarian model.
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crispr cas9 mediated gene knockin in the hydroid Hydractinia symbiolongicarpus
BMC Genomics, 2018Co-Authors: Steven M. Sanders, Uri Frank, Christine E. Schnitzler, Hakima Flici, Brooke M. Riscoe, Gregory A. Gibson, Alan M. Watson, Andreas D. Baxevanis, Julia Hughes, Matthew L NicotraAbstract:Hydractinia symbiolongicarpus, a colonial cnidarian, is a tractable model system for many cnidarian-specific and general biological questions. Until recently, tests of gene function in Hydractinia have relied on laborious forward genetic approaches, randomly integrated transgenes, or transient knockdown of mRNAs. Here, we report the use of CRISPR/Cas9 genome editing to generate targeted genomic insertions in H. symbiolonigcarpus. We used CRISPR/Cas9 to promote homologous recombination of two fluorescent reporters, eGFP and tdTomato, into the Eukaryotic elongation factor 1 alpha (Eef1a) locus. We demonstrate that the transgenes are expressed ubiquitously and are stable over two generations of breeding. We further demonstrate that CRISPR/Cas9 genome editing can be used to mark endogenous proteins with FLAG or StrepII-FLAG affinity tags to enable in vivo and ex vivo protein studies. This is the first account of CRISPR/Cas9 mediated knockins in Hydractinia and the first example of the germline transmission of a CRISPR/Cas9 inserted transgene in a cnidarian. The ability to precisely insert exogenous DNA into the Hydractinia genome will enable sophisticated genetic studies and further development of functional genomics tools in this understudied cnidarian model.
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CRISPR/Cas9-mediated gene knockin in the hydroid Hydractinia symbiolongicarpus
2018Co-Authors: Steven M. Sanders, Uri Frank, Christine E. Schnitzler, Hakima Flici, Brooke M. Riscoe, Gregory A. Gibson, Alan M. Watson, Julia Hughes, Andreas D. BaxevanisAbstract:Abstract Background Hydractinia symbiolongicarpus, a colonial cnidarian, is a tractable model system for many cnidarian-specific and general biological questions. Until recently, tests of gene function in Hydractinia have relied on laborious forward genetic approaches, randomly integrated transgenes, or transient knockdown of mRNAs. Results Here, we report the use of CRISPR/Cas9 genome editing to generate targeted genomic insertions in H. symbiolonigcarpus. We used CRISPR/Cas9 to promote homologous recombination of two fluorescent reporters, eGFP and tdTomato, into the Eukaryotic elongation factor 1 alpha (Eef1a) locus. We demonstrate that the transgenes are expressed ubiquitously and are stable over two generations of breeding. We further demonstrate that CRISPR/Cas9 genome editing can be used to mark endogenous proteins with FLAG or StrepII-FLAG affinity tags to enable in vivo and ex vivo protein studies. Conclusions This is the first account of CRISPR/Cas9 mediated knockins in Hydractinia and the first example of the germline transmission of a CRISPR/Cas9 inserted transgene in a cnidarian. The ability to precisely insert exogenous DNA into the Hydractinia genome will enable sophisticated genetic studies and further development of functional genomics tools in this understudied cnidarian model.
Thomas Leitz - One of the best experts on this subject based on the ideXlab platform.
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The embryonic development of the cnidarian Hydractinia echinata
Evolution & development, 2014Co-Authors: Yulia Kraus, Hakima Flici, Thomas Leitz, Günter Plickert, Katrin Hensel, Uri FrankAbstract:SUMMARY With the rapid increase of the quantity of molecular data, many animals joined the ranks of the so-called ‘emerging models’ of Evo-Devo. One of the necessary steps in converting an emerging model into an established one is gaining comprehensive knowledge of its normal embryonic development. The marine colonial hydrozoan Hydractinia echinata – an excellent model for research on stem cells, metamorphosis, and allorecognition – has been studied for decades. Yet knowledge of its embryonic development remains fragmentary and incomplete. Here we provide a detailed account of H. echinata embryonic development using in vivo observations, histology, immunohistochemistry, and electron microscopy. Furthermore, we propose a model describing the cellular basis of the morphogenetic movements occurring during development and also reveal a functional link between canonical Wnt signaling and regional differences in the morphology of the embryo. Hydractinia embryogenesis is an example of the diversity and plasticity of hydrozoan development where multiple routes lead to the same result – the formation of a normal planula larva.
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Metamorphosis of Hydractinia echinata (Cnidaria) is caspase-dependent.
The International journal of developmental biology, 2006Co-Authors: Stefanie Seipp, Karola Wittig, Beate Stiening, Angelika Böttger, Thomas LeitzAbstract:Apoptotic cell death plays an important role in many developmental pathways in multicellular animals. Here, we show that metamorphosis in the basal invertebrate Hydractinia echinata (Cnidaria) depends on the activity of caspases, the central enzymes in apoptosis. Caspases are activated during metamorphosis and this activity can be measured with caspase-3 specific fluorogenic substrates. In affinity labelling experiments 23/25 kDa bands were obtained, which represented active caspase. Specific inhibition of caspase activity with caspase-3 inhibitors abolished metamorphosis completely, reversibly and in a dose-dependent manner. This suggests that caspase activity is indispensable for metamorphosis in Hydractinia echinata.
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The hydroid Hydractinia
BioEssays, 2001Co-Authors: Uri Frank, Thomas Leitz, Werner A. MüllerAbstract:The Cnidaria represent the most ancient eumetazoan phylum. Members of this group possess typical animal cells and tissues such as sensory cells, nerve cells, muscle cells and epithelia. Due to their unique phylogenetic position, cnidarians have traditionally been used as a reference group in various comparative studies. We propose the colonial marine hydroid, Hydractinia, as a convenient, versatile platform for basic and applied research in developmental biology, reproduction, immunology, environmental studies and more. In addition to being a typical cnidarian representative, Hydractinia offers many practical and theoretical advantages: studies that are feasible in Hydra like regeneration, pattern regulation, and cell renewal from stem cells, can be supplemented by genetic analyses and classical embryology in Hydractinia. Metamorphosis of the planula larva of Hydractinia can be used as a model for cell activation and communication and the presence of a genetically controlled allorecognition system makes it a suitable model for comparative immunology. Most importantly, Hydractinia may be manipulated at most aspects of its (short) life cycle. It has already been the subject of many studies in various disciplines, some of which are discussed in this essay.
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The hydroid Hydractinia: a versatile, informative cnidarian representative.
BioEssays : news and reviews in molecular cellular and developmental biology, 2001Co-Authors: Uri Frank, Thomas Leitz, Werner A. MüllerAbstract:The Cnidaria represent the most ancient eumetazoan phylum. Members of this group possess typical animal cells and tissues such as sensory cells, nerve cells, muscle cells and epithelia. Due to their unique phylogenetic position, cnidarians have traditionally been used as a reference group in various comparative studies. We propose the colonial marine hydroid, Hydractinia, as a convenient, versatile platform for basic and applied research in developmental biology, reproduction, immunology, environmental studies and more. In addition to being a typical cnidarian representative, Hydractinia offers many practical and theoretical advantages: studies that are feasible in Hydra like regeneration, pattern regulation, and cell renewal from stem cells, can be supplemented by genetic analyses and classical embryology in Hydractinia. Metamorphosis of the planula larva of Hydractinia can be used as a model for cell activation and communication and the presence of a genetically controlled allorecognition system makes it a suitable model for comparative immunology. Most importantly, Hydractinia may be manipulated at most aspects of its (short) life cycle. It has already been the subject of many studies in various disciplines, some of which are discussed in this essay.
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the role of glwamides in metamorphosis of Hydractinia echinata
Development Genes and Evolution, 1998Co-Authors: Jurgen Schmich, Stefan Trepel, Thomas LeitzAbstract:The metamorphosis of many marine invertebrate larvae is induced by environmental signals. Upon reception of the cues, internal signals have to be set in motion to convey information to all cells of the larvae. For hydrozoan larvae it was hypothesised that ectodermal neurosensory cells at the anterior part are those cells receptive of the inducer. Recently, it was shown that novel peptides with a common GLWamide terminus are found in Cnidaria. These peptides are located in a specific subset of the anterior sensory cells. It was hypothesised that the neuropeptides represent an internal signal coordinating the metamorphic process. In the current study we present further evidence for this hypothesis. Induction of metamorphosis is very specific for the GLWamide terminus and amidation is essential. The potency to metamorphose is strongly correlated with the presence of GLWamide-immunoreactive cell bodies. Our data fit our hypothesis about a very important role of GLWamides in the initiation of the morphogenetic processes very well.
Leo W. Buss - One of the best experts on this subject based on the ideXlab platform.
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genetic background and allorecognition phenotype in Hydractinia symbiolongicarpus
G3: Genes Genomes Genetics, 2011Co-Authors: Anahid E Powell, Andrea Gloriasoria, Stephen L. Dellaporta, María Angeles Moreno, Fadi G. Lakkis, Leo W. BussAbstract:The Hydractinia allorecognition complex (ARC) was initially identified as a single chromosomal interval using inbred and congenic lines. The production of defined lines necessarily homogenizes genetic background and thus may be expected to obscure the effects of unlinked allorecognition loci should they exist. Here, we report the results of crosses in which inbred lines were out-crossed to wild-type animals in an attempt to identify dominant, codominant, or incompletely dominant modifiers of allorecognition. A claim for the existence of modifiers unlinked to ARC was rejected for three different genetic backgrounds. Estimates of the genetic map distance of ARC in two wild-type haplotypes differed markedly from one another and from that measured in congenic lines. These results suggest that additional allodeterminants exist in the Hydractinia ARC.
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Genetic Diversity of the Allodeterminant alr2 in Hydractinia symbiolongicarpus
Molecular biology and evolution, 2010Co-Authors: Rafael D Rosengarten, Leo W. Buss, Fadi G. Lakkis, Maria A. Moreno, Stephen L. DellaportaAbstract:Hydractinia symbiolongicarpus, a colonial cnidarian (class Hydrozoa) epibiont on hermit crab shells, is well established as a model for genetic studies of allorecognition. Recently, two linked loci, allorecognition (alr) 1 and alr2, were identified by positional cloning and shown to be major determinants of histocompatibility. Both genes encode putative transmembrane proteins with hypervariable extracellular domains similar to immunoglobulin (Ig)-like domains. We sought to characterize the naturally occurring variation at the alr2 locus and to understand the origins of this molecular diversity. We examined full-length cDNA coding sequences derived from a sample of 21 field-collected colonies, including 18 chosen haphazardly and two laboratory reference strains. Of the 35 alleles recovered from the 18 unbiased samples, 34 encoded unique gene products. We identified two distinct structural classes of alleles that varied over a large central region of the gene but both possessed highly polymorphic extracellular domains I, similar to an Ig-like V-set domain. The discovery of structurally chimeric alleles provided evidence that interallelic recombination may contribute to alr2 variation. Comparisons of the genomic region encompassing alr2 from two field-derived haplotypes and one laboratory reference sequence revealed a history of structural variation at the haplotype level as well. Maintenance of large numbers of equally rare alleles in a natural population is a hallmark of negative frequency–dependent selection and is expected to produce high levels of heterozygosity. The observed alr2 allelic diversity is comparable with that found in immune recognition molecules such as human leukocyte antigens, B cell Igs, or natural killer cell Ig-like receptors.
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Hydractinia Allodeterminant alr1 Resides in an Immunoglobulin Superfamily-like Gene Complex
Current biology : CB, 2010Co-Authors: Sabrina Rosa, Rafael D Rosengarten, Matthew L Nicotra, Anahid E Powell, Stephen L. Dellaporta, Fadi G. Lakkis, Maria A. Moreno, Jane Grimwood, Leo W. BussAbstract:Allorecognition, the ability to discriminate between self and nonself, is ubiquitous among colonial metazoans and widespread among aclonal taxa. Genetic models for the study of allorecognition have been developed in the jawed vertebrates, invertebrate chordate Botryllus, and cnidarian Hydractinia. In Botryllus, two genes contribute to the histocompatibility response, FuHC and fester. In the cnidarian Hydractinia, one of the two known allorecognition loci, alr2, has been isolated, and a second linked locus, alr1, has been mapped to the same chromosomal region, called the allorecognition complex (ARC). Here we isolate alr1 by positional cloning and report it to encode a transmembrane receptor protein with two hypervariable extracellular regions similar to immunoglobulin (Ig)-like domains. Variation in the extracellular domain largely predicts fusibility within and between laboratory strains and wild-type isolates. alr1 was found embedded in a family of immunoglobulin superfamily (IgSF)-like genes, thus establishing that the ARC histocompatibility complex is an invertebrate IgSF-like gene complex.
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Allorecognition and chimerism in an invertebrate model organism
Organogenesis, 2008Co-Authors: Fadi G. Lakkis, Stephen L. Dellaporta, Leo W. BussAbstract:The presence of highly specific histocompatibility reactions in colonial marine invertebrates that lack adaptive immune systems (such as the sponges, cnidarians, bryozoans, and ascidians) provides a unique opportunity to investigate the evolutionary roots of allorecognition and to explore whether homologous innate recognition systems exist in vertebrates. Conspecific interactions among adult animals in these groups are regulated by highly specific allorecognition systems that restrict somatic fusion to self or close kin. In Hydractinia (Cnidaria:Hydrozoa), fusion/rejection responses are controlled by two linked genetic loci. Alleles at each locus are co-dominantly inherited. Colonies fuse if they share at least one haplotype, reject if they share no haplotypes, and display transitory fusion if they share only one allele in a haplotype A¢Â€Â“ a pattern that echoes natural killer cell responses in mice and humans. Allorecognition in Hydractinia and other marine invertebrates serves as a safeguard against st...
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differential effect of allorecognition loci on phenotype in Hydractinia symbiolongicarpus cnidaria hydrozoa
Genetics, 2007Co-Authors: Anahid E Powell, Matthew L Nicotra, Stephen L. Dellaporta, María Angeles Moreno, Fadi G. Lakkis, Leo W. BussAbstract:The allorecognition complex of Hydractinia symbiolongicarpus is a chromosomal interval containing two loci, alr1 and alr2, that controls fusion between genetically distinct colonies. Recombination between these two loci has been associated with a heterogeneous class of phenotypes called transitory fusion. A large-scale backcross was performed to generate a population of colonies (N = 106) with recombination breakpoints within the allorecognition complex. Two distinct forms of transitory fusion were correlated with reciprocal recombination products, suggesting that alr1 and alr2 contributed differentially to the allorecognition response. Specifically, type I transitory fusion is associated with rapid and persistent separation of allogeneic tissues, whereas type II transitory fusion generates a patchwork of continuously fusing and separating tissues.
Tsutomu Sugiyama - One of the best experts on this subject based on the ideXlab platform.
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Control of planula migration by LWamide and RFamide neuropeptides in Hydractinia echinata.
Journal of Experimental Biology, 2004Co-Authors: Yuki Katsukura, Charles N. David, Cornelis J. P. Grimmelikhuijzen, Hiroshi Ando, Tsutomu SugiyamaAbstract:SUMMARY Planula larvae of Hydractinia echinata (Cnidaria) settled on a substratum migrate toward light. We observed that planula migration is not a continuous process. Instead, it consists of repeating cycles of active migration (about 8 min on average) and inactive resting periods (about 26 min on average). This pattern of periodic migration is regulated by LWamide and RFamide neuropeptides. LWamide (10-8 mol l-1) stimulates migration primarily by making the active periods longer, whereas RFamide (10-7 mol l-1) inhibits migration by blocking the initiation and also shortening the length of the active periods. Since sensory neurons containing LWamides and RFamides are present in planula larvae, it appears likely that planula migration is regulated by the release of endogenous neuropeptides in response to environmental cues.
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Inhibition of metamorphosis by RFamide neuropeptides in planula larvae of Hydractinia echinata
Development Genes and Evolution, 2003Co-Authors: Yuki Katsukura, Charles N. David, Cornelis J. P. Grimmelikhuijzen, Tsutomu SugiyamaAbstract:The primitive nervous system in planula larvae of Hydractinia echinata (Cnidaria) has sensory neurons containing LWamide or RFamide neuropeptides. LWamides have been shown to induce metamorphosis of planula larvae into adult polyps. We report here that RFamides act antagonistically to LWamides. RFamides inhibit metamorphosis when applied to planula larvae during metamorphosis induction by treatment with LWamides (or other inducing agents such as CsCl ions, diacylglycerol and bacterial inducers). Our results show further that RFamides act downstream of LWamide release, presumably directly on target cells mediating metamorphosis. These observations support a model in which metamorphosis in H. echinata is regulated by sensory neurons secreting LWamides and RFamides in response to environmental cues.
Werner A. Müller - One of the best experts on this subject based on the ideXlab platform.
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Hydractinia, a pioneering model for stem cell biology and reprogramming somatic cells to pluripotency.
The International journal of developmental biology, 2012Co-Authors: Günter Plickert, Uri Frank, Werner A. MüllerAbstract:Hydractinia, a representative marine colonial hydroid, was the first organism in the history of biology in which migratory precursors of germ cells were described and termed "stem cells" (Weismann, 1883). These stem cells, now known as interstitial cells (i-cells), are thought to remain pluripotent throughout their life. Using animals depleted of their own stem cells and repopulated with allogeneic mutant donor stem cells, it was shown that Hydractinia i-cells differentiate into any cell type including epithelial cells and germ cells that express germ line markers such as Vasa, Piwi and Nanos. In Hydra, i-cells also provide germ cells and somatic cells with the exception of epithelial cells. The latter derive from two subpopulations of differentiated epithelial cells with self-renewal capacity. In Hydractinia, forced expression of the Oct4-like transcription factor, Polynem (Pln), in epithelial cells transforms them into stem cells that develop neoplasms. I-cells express the Wnt-receptor Frizzled and are Wnt responsive. Activation of Wnt signaling induces the production of numerous nematocytes (stinging cells) and nerve cells. In parallel, supernumerary tentacles develop. I-cells also express Myc and Nanos. Their misexpression causes severe developmental defects. Hydractinia polyp buds arise from aggregating stem cells, in contrast to Hydra buds, which derive from evaginating epithelial cells. Wnt activation increases budding frequency and the emergence of ectopic head structures. The potential of stem cells to invade neighbors may have provided selection pressure for the evolution of allorecognition and histo-incompatibility. Hence, Hydractinia have now attained the position of a powerful model in stem cell research, axis formation and allorecognition.
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Autoaggressive, multi-headed and other mutant phenotypes in Hydractinia echinata (Cnidaria: Hydrozoa).
The International journal of developmental biology, 2002Co-Authors: Werner A. MüllerAbstract:In an inbreeding program conducted with the colonial hydroid Hydractinia echinata, each F1 mating produced up to 50% F2 offspring displaying an aberrant, clone-constant phenotype, hence referred to as mutant strain. In autoaggressive strains, in one or several areas of the colony autoreactive stolons direct their aggressive devices (stolon tips filled with cytotoxic stinging cells), normally used to kill allogeneic competitors for living space, towards neighboring stolons or polyps (hydranths) of their own colony. In these areas tumor-like masses of self-aggressive stolons were formed, in severe cases causing the death of the colony. Based on previous genetic studies, the interpretation proposed here attributes autoaggressive behavior to a mosaic-type alternative expression of arl (allorecognition) alleles in heterozygous individuals. Developmental mutant strains termed He-mh form supernumerary heads during regeneration and normal development as well. Common to all He-mh phenotypes isthe production of additional headsalong the bodycolumn of fully-grown polyps. The heads give rise to complete hydranths connected by a tube that derives from the gastric region of the original polyp and eventually transforms into a stolon. In bastol strains, polyps convert the basal region of their body column into a periderm-covered stolon from which the residual apical hydranth detaches. Colonies expressing both the He-mh and the bastol (bst) phenotype frequently lose detaching multi-headed hydranths and the colony disintegrates. The large number of mutant F2 offspring reveals high genetic variability in Hydractinia.
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The hydroid Hydractinia
BioEssays, 2001Co-Authors: Uri Frank, Thomas Leitz, Werner A. MüllerAbstract:The Cnidaria represent the most ancient eumetazoan phylum. Members of this group possess typical animal cells and tissues such as sensory cells, nerve cells, muscle cells and epithelia. Due to their unique phylogenetic position, cnidarians have traditionally been used as a reference group in various comparative studies. We propose the colonial marine hydroid, Hydractinia, as a convenient, versatile platform for basic and applied research in developmental biology, reproduction, immunology, environmental studies and more. In addition to being a typical cnidarian representative, Hydractinia offers many practical and theoretical advantages: studies that are feasible in Hydra like regeneration, pattern regulation, and cell renewal from stem cells, can be supplemented by genetic analyses and classical embryology in Hydractinia. Metamorphosis of the planula larva of Hydractinia can be used as a model for cell activation and communication and the presence of a genetically controlled allorecognition system makes it a suitable model for comparative immunology. Most importantly, Hydractinia may be manipulated at most aspects of its (short) life cycle. It has already been the subject of many studies in various disciplines, some of which are discussed in this essay.
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The hydroid Hydractinia: a versatile, informative cnidarian representative.
BioEssays : news and reviews in molecular cellular and developmental biology, 2001Co-Authors: Uri Frank, Thomas Leitz, Werner A. MüllerAbstract:The Cnidaria represent the most ancient eumetazoan phylum. Members of this group possess typical animal cells and tissues such as sensory cells, nerve cells, muscle cells and epithelia. Due to their unique phylogenetic position, cnidarians have traditionally been used as a reference group in various comparative studies. We propose the colonial marine hydroid, Hydractinia, as a convenient, versatile platform for basic and applied research in developmental biology, reproduction, immunology, environmental studies and more. In addition to being a typical cnidarian representative, Hydractinia offers many practical and theoretical advantages: studies that are feasible in Hydra like regeneration, pattern regulation, and cell renewal from stem cells, can be supplemented by genetic analyses and classical embryology in Hydractinia. Metamorphosis of the planula larva of Hydractinia can be used as a model for cell activation and communication and the presence of a genetically controlled allorecognition system makes it a suitable model for comparative immunology. Most importantly, Hydractinia may be manipulated at most aspects of its (short) life cycle. It has already been the subject of many studies in various disciplines, some of which are discussed in this essay.
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Specificity and early ontogeny of historecognition in the hydroid Hydractinia
Journal of Experimental Zoology, 1992Co-Authors: R. G. Lange, Matthew H. Dick, Werner A. MüllerAbstract:The marine hydroid Hydractinia is a model system for study of historecognition in invertebrates. Present knowledge of this system comes from fusibility studies involving intraspecific (i.e., isogeneic and allogeneic) encounters of adult-stage stolonal tissues. Little is known about the ability of Hydractinia to recognize and respond to xenogeneic tissue, about allorecognition by tissues other than stolonal, and about the ontogeny of historecognition. We have investigated these questions with stolonal-encounter and grafting experiments, using the species H. echinata and H. symbiolongicarpus. We find that (a) Hydractinia employs the nematocyst effector system against the closely related hydroid Podocoryne and the more distantly related Eirene; (b) unlike intraspecific encounters, these interspecific encounters elicit nematocyst discharge by Hydractinia over a distance of up to 50 μm prior to stolonal contact; (c) the capability for historecognition is not restricted to stolonal tissues; (d) the capacity to display incompatibility, or rejection, arises between the late larval stage and early post-metamorphosis; and (e) embryo grafts of H. symbiolongicarpus, but not those of H. echinata, appeared to show limited tolerization. © 1992 Wiley-Liss, Inc.
