Two-color double-labeling in situ hybridization of whole-mount Hydra using RNA probes for five different Hydra neuropeptide preprohormones: evidence for colocalization

Hansen, Georg Nørgaard; Williamson, Michael; Grimmelikhuijzen, Cornelis J. P.

doi:10.1007/s004410000240

Cited by 49 publications

(13 citation statements)

References 38 publications

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“…These findings suggest the presence of HyNaC2/9/7 and HyNaC2/10/7 heterotrimers at the peduncle region. Since neurons expressing the preprohormone A gene that encodes the Hydra-RFamides I to IV are present at the tentacle bases, hypostome, upper gastric region and peduncle [ 27 , 31 , 39 ], it is possible that cells expressing HyNaCs in the peduncle make synaptic junctions with neurons expressing Hydra-RFamides.…”

Section: Resultsmentioning

confidence: 99%

“…A more definite answer to this question needs a survey of the full repertoire of DEG/ENaCs in Hydra to establish whether all DEG/ENaCs in Hydra are peptide-gated channels. Moreover, the presence of many more neuropeptides in the Hydra nervous system [ 30 ] and the presence of the precursors that encode Hydra-RFamides I and II [ 27 ] at the peduncle region [ 31 ] raises the questions of the existence of HyNaCs that are gated by peptides other than Hydra-RFamides I and II or that are expressed at the peduncle and activated by Hydra-RFamides I and II.…”

Section: Introductionmentioning

confidence: 99%

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The comprehensive analysis of DEG/ENaC subunits in Hydrareveals a large variety of peptide-gated channels, potentially involved in neuromuscular transmission

Assmann

Kuhn²,

Dürrnagel

et al. 2014

BMC Biol

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BackgroundIt is generally the case that fast transmission at neural synapses is mediated by small molecule neurotransmitters. The simple nervous system of the cnidarian Hydra, however, contains a large repertoire of neuropeptides and it has been suggested that neuropeptides are the principal transmitters of Hydra. An ion channel directly gated by Hydra-RFamide neuropeptides has indeed been identified in Hydra – the Hydra Na+ channel (HyNaC) 2/3/5, which is expressed at the oral side of the tentacle base. Hydra-RFamides are more widely expressed, however, being found in neurons of the head and peduncle region. Here, we explore whether further peptide-gated HyNaCs exist, where in the animal they are expressed, and whether they are all gated by Hydra-RFamides.ResultsWe report molecular cloning of seven new HyNaC subunits – HyNaC6 to HyNaC12, all of which are members of the DEG/ENaC gene family. In Xenopus oocytes, these subunits assemble together with the four already known subunits into thirteen different ion channels that are directly gated by Hydra-RFamide neuropeptides with high affinity (up to 40 nM). In situ hybridization suggests that HyNaCs are expressed in epitheliomuscular cells at the oral and the aboral side of the tentacle base and at the peduncle. Moreover, diminazene, an inhibitor of HyNaCs, delayed tentacle movement in live Hydra.ConclusionsOur results show that Hydra has a large variety of peptide-gated ion channels that are activated by a restricted number of related neuropeptides. The existence and expression pattern of these channels, and behavioral effects induced by channel blockers, suggests that Hydra co-opted neuropeptides for fast neuromuscular transmission.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-014-0084-2) contains supplementary material, which is available to authorized users.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The comprehensive analysis of DEG/ENaC subunits in Hydrareveals a large variety of peptide-gated channels, potentially involved in neuromuscular transmission

Assmann

Kuhn²,

Dürrnagel

et al. 2014

BMC Biol

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“…At present, we can only speculate on the role of Ca 2+ permeability for the physiological function of HyNaCs. HyNaCs are expressed at the base of the tentacles, perhaps in epitheliomuscular cells, and the preprohormone gene that encodes their ligands (Darmer et al, 1998), Hydra-RFamides I and II, is expressed in adjacent nerve cells of the hypostome and upper gastric region (Hansen et al, 2000). Therefore, it has been speculated that HyNaCs contribute to coordinate the Hydra feeding response (Golubovic et al, 2007; Dürrnagel et al, 2010).…”

Section: Discussionmentioning

confidence: 99%

High Ca2+ permeability of a peptide-gated DEG/ENaC from Hydra

Dürrnagel

Falkenburger

Gründer

2012

Journal of General Physiology

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Degenerin/epithelial Na+ channels (DEG/ENaCs) are Na+ channels that are blocked by the diuretic amiloride. In general, they are impermeable for Ca2+ or have a very low permeability for Ca2+. We describe here, however, that a DEG/ENaC from the cnidarian Hydra magnipapillata, the Hydra Na+ channel (HyNaC), is highly permeable for Ca2+ (PCa/PNa = 3.8). HyNaC is directly gated by Hydra neuropeptides, and in Xenopus laevis oocytes expressing HyNaCs, RFamides elicit currents with biphasic kinetics, with a fast transient component and a slower sustained component. Although it was previously reported that the sustained component is unselective for monovalent cations, the selectivity of the transient component had remained unknown. Here, we show that the transient current component arises from secondary activation of the Ca2+-activated Cl− channel (CaCC) of Xenopus oocytes. Inhibiting the activation of the CaCC leads to a simple on–off response of peptide-activated currents with no apparent desensitization. In addition, we identify a conserved ring of negative charges at the outer entrance of the HyNaC pore that is crucial for the high Ca2+ permeability, presumably by attracting divalent cations to the pore. At more positive membrane potentials, the binding of Ca2+ to the ring of negative charges increasingly blocks HyNaC currents. Thus, HyNaC is the first member of the DEG/ENaC gene family with a high Ca2+ permeability.

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“…Similar comparisons of the expression of Lhx family members and the many documented neural populations in Hydra [16-19] will be invaluable in understanding the evolution of neural patterning mechanisms. In this study, we found that the four Lhx genes encoded by the Hydra genome are expressed in adults.…”

Section: Discussionmentioning

confidence: 99%

Early evolution of the LIM homeobox gene family

Srivastava

Larroux

et al. 2010

BMC Biol

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BackgroundLIM homeobox (Lhx) transcription factors are unique to the animal lineage and have patterning roles during embryonic development in flies, nematodes and vertebrates, with a conserved role in specifying neuronal identity. Though genes of this family have been reported in a sponge and a cnidarian, the expression patterns and functions of the Lhx family during development in non-bilaterian phyla are not known.ResultsWe identified Lhx genes in two cnidarians and a placozoan and report the expression of Lhx genes during embryonic development in Nematostella and the demosponge Amphimedon. Members of the six major LIM homeobox subfamilies are represented in the genomes of the starlet sea anemone, Nematostella vectensis, and the placozoan Trichoplax adhaerens. The hydrozoan cnidarian, Hydra magnipapillata, has retained four of the six Lhx subfamilies, but apparently lost two others. Only three subfamilies are represented in the haplosclerid demosponge Amphimedon queenslandica. A tandem cluster of three Lhx genes of different subfamilies and a gene containing two LIM domains in the genome of T. adhaerens (an animal without any neurons) indicates that Lhx subfamilies were generated by tandem duplication. This tandem cluster in Trichoplax is likely a remnant of the original chromosomal context in which Lhx subfamilies first appeared. Three of the six Trichoplax Lhx genes are expressed in animals in laboratory culture, as are all Lhx genes in Hydra. Expression patterns of Nematostella Lhx genes correlate with neural territories in larval and juvenile polyp stages. In the aneural demosponge, A. queenslandica, the three Lhx genes are expressed widely during development, including in cells that are associated with the larval photosensory ring.ConclusionsThe Lhx family expanded and diversified early in animal evolution, with all six subfamilies already diverged prior to the cnidarian-placozoan-bilaterian last common ancestor. In Nematostella, Lhx gene expression is correlated with neural territories in larval and juvenile polyp stages. This pattern is consistent with a possible role in patterning the Nematostella nervous system. We propose a scenario in which Lhx genes play a homologous role in neural patterning across eumetazoans.

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Two-color double-labeling in situ hybridization of whole-mount Hydra using RNA probes for five different Hydra neuropeptide preprohormones: evidence for colocalization

Cited by 49 publications

References 38 publications

The comprehensive analysis of DEG/ENaC subunits in Hydrareveals a large variety of peptide-gated channels, potentially involved in neuromuscular transmission

The comprehensive analysis of DEG/ENaC subunits in Hydrareveals a large variety of peptide-gated channels, potentially involved in neuromuscular transmission

High Ca2+ permeability of a peptide-gated DEG/ENaC from Hydra

Early evolution of the LIM homeobox gene family

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