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Ehrhardt E, Whitehead SC, Namiki S, Minegishi R, Siwanowicz I, Feng K, Otsuna H, Meissner GW, Stern D, Truman J, Shepherd D, Dickinson MH, Ito K, Dickson BJ, Cohen I, Card GM, Korff W. Single-cell type analysis of wing premotor circuits in the ventral nerve cord of Drosophila melanogaster. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.31.542897. [PMID: 37398009 PMCID: PMC10312520 DOI: 10.1101/2023.05.31.542897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
To perform most behaviors, animals must send commands from higher-order processing centers in the brain to premotor circuits that reside in ganglia distinct from the brain, such as the mammalian spinal cord or insect ventral nerve cord. How these circuits are functionally organized to generate the great diversity of animal behavior remains unclear. An important first step in unraveling the organization of premotor circuits is to identify their constituent cell types and create tools to monitor and manipulate these with high specificity to assess their function. This is possible in the tractable ventral nerve cord of the fly. To generate such a toolkit, we used a combinatorial genetic technique (split-GAL4) to create 195 sparse driver lines targeting 198 individual cell types in the ventral nerve cord. These included wing and haltere motoneurons, modulatory neurons, and interneurons. Using a combination of behavioral, developmental, and anatomical analyses, we systematically characterized the cell types targeted in our collection. Taken together, the resources and results presented here form a powerful toolkit for future investigations of neural circuits and connectivity of premotor circuits while linking them to behavioral outputs.
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Affiliation(s)
- Erica Ehrhardt
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Dr, Ashburn, Virginia 20147, USA
- Institute of Zoology, University of Cologne, Zülpicher Str 47b, 50674 Cologne, Germany
| | - Samuel C Whitehead
- Physics Department, Cornell University, 271 Clark Hall, Ithaca, New York 14853, USA
| | - Shigehiro Namiki
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Dr, Ashburn, Virginia 20147, USA
| | - Ryo Minegishi
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Dr, Ashburn, Virginia 20147, USA
| | - Igor Siwanowicz
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Dr, Ashburn, Virginia 20147, USA
| | - Kai Feng
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Dr, Ashburn, Virginia 20147, USA
- Queensland Brain Institute, University of Queensland, 79 Upland Rd, Brisbane, QLD, 4072, Australia
| | - Hideo Otsuna
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Dr, Ashburn, Virginia 20147, USA
| | - FlyLight Project Team
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Dr, Ashburn, Virginia 20147, USA
| | - Geoffrey W Meissner
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Dr, Ashburn, Virginia 20147, USA
| | - David Stern
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Dr, Ashburn, Virginia 20147, USA
| | - Jim Truman
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Dr, Ashburn, Virginia 20147, USA
- Department of Biology, University of Washington, Seattle, Washington 98195, USA
| | - David Shepherd
- School of Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Life Sciences Building, Southampton SO17 1BJ
| | - Michael H. Dickinson
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Dr, Ashburn, Virginia 20147, USA
- California Institute of Technology, 1200 E California Blvd, Pasadena, California 91125, USA
| | - Kei Ito
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Dr, Ashburn, Virginia 20147, USA
- Institute of Zoology, University of Cologne, Zülpicher Str 47b, 50674 Cologne, Germany
| | - Barry J Dickson
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Dr, Ashburn, Virginia 20147, USA
| | - Itai Cohen
- Physics Department, Cornell University, 271 Clark Hall, Ithaca, New York 14853, USA
| | - Gwyneth M Card
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Dr, Ashburn, Virginia 20147, USA
| | - Wyatt Korff
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Dr, Ashburn, Virginia 20147, USA
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Ssempijja F, Dare SS, Bukenya EEM, Kasozi KI, Kenganzi R, Fernandez EM, Vicente-Crespo M. Attenuation of Seizures, Cognitive Deficits, and Brain Histopathology by Phytochemicals of Imperata cylindrica (L.) P. Beauv (Poaceae) in Acute and Chronic Mutant Drosophila melanogaster Epilepsy Models. J Evid Based Integr Med 2023; 28:2515690X231160191. [PMID: 36866635 PMCID: PMC9989407 DOI: 10.1177/2515690x231160191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 08/09/2022] [Accepted: 02/06/2023] [Indexed: 03/04/2023] Open
Abstract
Imperata cylindrica is a globally distributed plant known for its antiepileptic attributes, but there is a scarcity of robust evidence for its efficacy. The study investigated neuroprotective attributes of Imperata cylindrica root extract on neuropathological features of epilepsy in a Drosophila melanogaster mutant model of epilepsy. It was conducted on 10-day-old (at the initiation of study) male post-eclosion bang-senseless paralytic Drosophila (parabss1) involved acute (1-3 h) and chronic (6-18 days) experiments; n = 50 flies per group (convulsions tests); n = 100 flies per group (learning/memory tests and histological examination). Administrations were done in 1 g standard fly food, per os. The mutant flies of study (parabss1) showed marked age-dependent progressive brain neurodegeneration and axonal degeneration, significant (P < 0.05) bang sensitivity and convulsions, and cognitive deficits due to up-regulation of the paralytic gene in our mutants. The neuropathological findings were significantly (P < 0.05) alleviated in dose and duration-dependent fashions to near normal/normal after acute and chronic treatment with extract similar to sodium valproate. Therefore, para is expressed in neurons of brain tissues in our mutant flies to bring about epilepsy phenotypes and behaviors of the current juvenile and old-adult mutant D. melanogaster models of epilepsy. The herb exerts neuroprotection by anticonvulsant and antiepileptogenic mechanisms in mutant D. melanogaster due to plant flavonoids, polyphenols, and chromones (1 and 2) which exert antioxidative and receptor or voltage-gated sodium ion channels' inhibitory properties, and thus causing reduced inflammation and apoptosis, increased tissue repair, and improved cell biology in the brain of mutant flies. The methanol root extract provides anticonvulsant and antiepileptogenic medicinal values which protect epileptic D. melanogaster. Therefore, the herb should be advanced for more experimental and clinical studies to confirm its efficacy in treating epilepsy.
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Affiliation(s)
- Fred Ssempijja
- Department of Anatomy, Faculty of Medicine, Mbarara University of Science and Technology, P.O Box 1410, Mbarara, Uganda
- Department of Anatomy, Faculty of Biomedical Sciences, Kampala International University, Western Campus, P.O Box 71, Ishaka, Bushenyi, Uganda
| | - Samuel Sunday Dare
- Department of Anatomy, Faculty of Biomedical Sciences, Kampala International University, Western Campus, P.O Box 71, Ishaka, Bushenyi, Uganda
- School of Medicine, Kabale University, P.O Box 317, Kabale, Uganda
| | - Edmund E. M. Bukenya
- Department of Anatomy, Faculty of Biomedical Sciences, Kampala International University, Western Campus, P.O Box 71, Ishaka, Bushenyi, Uganda
- School of Medicine, Kabale University, P.O Box 317, Kabale, Uganda
| | | | - Ritah Kenganzi
- Department of Medical Laboratory Sciences, School of Allied Health Sciences, Kampala International University Teaching Hospital, P.O Box 71, Ishaka, Bushenyi, Uganda
| | - Edgar Mario Fernandez
- Department of Anatomy, Faculty of Biomedical Sciences, Kampala International University, Western Campus, P.O Box 71, Ishaka, Bushenyi, Uganda
| | - Marta Vicente-Crespo
- Institute of Biomedical Research, Kampala International University Western Campus, P.O Box 71, Bushenyi, Uganda
- Department of Biochemistry, Faculty of Biomedical Sciences, Kampala International University Western Campus, P.O Box 71, Bushenyi, Uganda
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Drosophila carrying epilepsy-associated variants in the vitamin B6 metabolism gene PNPO display allele- and diet-dependent phenotypes. Proc Natl Acad Sci U S A 2022; 119:2115524119. [PMID: 35217610 PMCID: PMC8892510 DOI: 10.1073/pnas.2115524119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/10/2022] [Indexed: 12/02/2022] Open
Abstract
Both genetic and environmental factors contribute to epilepsy. Understanding their contributions and interactions helps disease management. However, it is often challenging to study gene–environment interaction in humans due to their heterogeneous genetic background and less controllable environmental factors. The fruit fly, Drosophila melanogaster, has been proven to be a powerful model to study human diseases, including epilepsy. We generated knock-in flies carrying different epilepsy-associated pyridox(am)ine 5′-phosphate oxidase (PNPO) alleles and studied the developmental, behavioral, electrophysiological, and fitness effects of each mutant allele under different dietary conditions. We showed that phenotypes in knock-in flies are allele and diet dependent, providing clues for timely and specific diet interventions. Our results offer biological insights into mechanisms underlying phenotypic variations and specific therapeutic strategies. Pyridox(am)ine 5′-phosphate oxidase (PNPO) catalyzes the rate-limiting step in the synthesis of pyridoxal 5′-phosphate (PLP), the active form of vitamin B6 required for the synthesis of neurotransmitters gamma-aminobutyric acid (GABA) and the monoamines. Pathogenic variants in PNPO have been increasingly identified in patients with neonatal epileptic encephalopathy and early-onset epilepsy. These patients often exhibit different types of seizures and variable comorbidities. Recently, the PNPO gene has also been implicated in epilepsy in adults. It is unclear how these phenotypic variations are linked to specific PNPO alleles and to what degree diet can modify their expression. Using CRISPR-Cas9, we generated four knock-in Drosophila alleles, hWT, hR116Q, hD33V , and hR95H, in which the endogenous Drosophila PNPO was replaced by wild-type human PNPO complementary DNA (cDNA) and three epilepsy-associated variants. We found that these knock-in flies exhibited a wide range of phenotypes, including developmental impairments, abnormal locomotor activities, spontaneous seizures, and shortened life span. These phenotypes are allele dependent, varying with the known biochemical severity of these mutations and our characterized molecular defects. We also showed that diet treatments further diversified the phenotypes among alleles, and PLP supplementation at larval and adult stages prevented developmental impairments and seizures in adult flies, respectively. Furthermore, we found that hR95H had a significant dominant-negative effect, rendering heterozygous flies susceptible to seizures and premature death. Together, these results provide biological bases for the various phenotypes resulting from multifunction of PNPO, specific molecular and/or genetic properties of each PNPO variant, and differential allele–diet interactions.
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Abstract
Hypersynchronous neural activity is a characteristic feature of seizures. Although many Drosophila mutants of epilepsy-related genes display clear behavioral spasms and motor unit hyperexcitability, field potential measurements of aberrant hypersynchronous activity across brain regions during seizures have yet to be described. Here, we report a straightforward method to observe local field potentials (LFPs) from the Drosophila brain to monitor ensemble neural activity during seizures in behaving tethered flies. High frequency stimulation across the brain reliably triggers a stereotypic sequence of electroconvulsive seizure (ECS) spike discharges readily detectable in the dorsal longitudinal muscle (DLM) and coupled with behavioral spasms. During seizure episodes, the LFP signal displayed characteristic large-amplitude oscillations with a stereotypic temporal correlation to DLM flight muscle spiking. ECS-related LFP events were clearly distinct from rest- and flight-associated LFP patterns. We further characterized the LFP activity during different types of seizures originating from genetic and pharmacological manipulations. In the 'bang-sensitive' sodium channel mutant bangsenseless (bss), the LFP pattern was prolonged, and the temporal correlation between LFP oscillations and DLM discharges was altered. Following administration of the pro-convulsant GABAA blocker picrotoxin, we uncovered a qualitatively different LFP activity pattern, which consisted of a slow (1-Hz), repetitive, waveform, closely coupled with DLM bursting and behavioral spasms. Our approach to record brain LFPs presents an initial framework for electrophysiological analysis of the complex brain-wide activity patterns in the large collection of Drosophila excitability mutants.
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Affiliation(s)
- Atulya Iyengar
- Department of Biology, and Iowa Neuroscience Institute, University of Iowa, Iowa City, IA, USA
| | - Chun-Fang Wu
- Department of Biology, and Iowa Neuroscience Institute, University of Iowa, Iowa City, IA, USA
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Characterization of Seizure Induction Methods in Drosophila. eNeuro 2021; 8:ENEURO.0079-21.2021. [PMID: 34330816 PMCID: PMC8387149 DOI: 10.1523/eneuro.0079-21.2021] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 06/02/2021] [Accepted: 06/10/2021] [Indexed: 02/07/2023] Open
Abstract
Epilepsy is one of the most common neurologic disorders. Around one third of patients do not respond to current medications. This lack of treatment indicates a need for better understanding of the underlying mechanisms and, importantly, the identification of novel targets for drug manipulation. The fruit fly Drosophila melanogaster has a fast reproduction time, powerful genetics, and facilitates large sample sizes, making it a strong model of seizure mechanisms. To better understand behavioral and physiological phenotypes across major fly seizure genotypes we systematically measured seizure severity and secondary behavioral phenotypes at both the larval and adult stage. Comparison of several seizure-induction methods; specifically electrical, mechanical and heat induction, show that larval electroshock is the most effective at inducing seizures across a wide range of seizure-prone mutants tested. Locomotion in adults and larvae was found to be non-predictive of seizure susceptibility. Recording activity in identified larval motor neurons revealed variations in action potential (AP) patterns, across different genotypes, but these patterns did not correlate with seizure susceptibility. To conclude, while there is wide variation in mechanical induction, heat induction, and secondary phenotypes, electroshock is the most consistent method of seizure induction across known major seizure genotypes in Drosophila.
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Straub J, Gregor A, Sauerer T, Fliedner A, Distel L, Suchy C, Ekici AB, Ferrazzi F, Zweier C. Genetic interaction screen for severe neurodevelopmental disorders reveals a functional link between Ube3a and Mef2 in Drosophila melanogaster. Sci Rep 2020; 10:1204. [PMID: 31988313 PMCID: PMC6985129 DOI: 10.1038/s41598-020-58182-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2019] [Accepted: 01/13/2020] [Indexed: 11/09/2022] Open
Abstract
Neurodevelopmental disorders (NDDs) are clinically and genetically extremely heterogeneous with shared phenotypes often associated with genes from the same networks. Mutations in TCF4, MEF2C, UBE3A, ZEB2 or ATRX cause phenotypically overlapping, syndromic forms of NDDs with severe intellectual disability, epilepsy and microcephaly. To characterize potential functional links between these genes/proteins, we screened for genetic interactions in Drosophila melanogaster. We induced ubiquitous or tissue specific knockdown or overexpression of each single orthologous gene (Da, Mef2, Ube3a, Zfh1, XNP) and in pairwise combinations. Subsequently, we assessed parameters such as lethality, wing and eye morphology, neuromuscular junction morphology, bang sensitivity and climbing behaviour in comparison between single and pairwise dosage manipulations. We found most stringent evidence for genetic interaction between Ube3a and Mef2 as simultaneous dosage manipulation in different tissues including glia, wing and eye resulted in multiple phenotype modifications. We subsequently found evidence for physical interaction between UBE3A and MEF2C also in human cells. Systematic pairwise assessment of the Drosophila orthologues of five genes implicated in clinically overlapping, severe NDDs and subsequent confirmation in a human cell line revealed interactions between UBE3A/Ube3a and MEF2C/Mef2, thus contributing to the characterization of the underlying molecular commonalities.
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Affiliation(s)
- Jonas Straub
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054, Erlangen, Germany
| | - Anne Gregor
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054, Erlangen, Germany
| | - Tatjana Sauerer
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054, Erlangen, Germany
| | - Anna Fliedner
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054, Erlangen, Germany
| | - Laila Distel
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054, Erlangen, Germany
| | - Christine Suchy
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054, Erlangen, Germany
| | - Arif B Ekici
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054, Erlangen, Germany
| | - Fulvia Ferrazzi
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054, Erlangen, Germany
| | - Christiane Zweier
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054, Erlangen, Germany.
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Hill AS, Jain P, Folan NE, Ben-Shahar Y. The Drosophila ERG channel seizure plays a role in the neuronal homeostatic stress response. PLoS Genet 2019; 15:e1008288. [PMID: 31393878 PMCID: PMC6687100 DOI: 10.1371/journal.pgen.1008288] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 07/04/2019] [Indexed: 11/24/2022] Open
Abstract
Neuronal physiology is particularly sensitive to acute stressors that affect excitability, many of which can trigger seizures and epilepsies. Although intrinsic neuronal homeostasis plays an important role in maintaining overall nervous system robustness and its resistance to stressors, the specific genetic and molecular mechanisms that underlie these processes are not well understood. Here we used a reverse genetic approach in Drosophila to test the hypothesis that specific voltage-gated ion channels contribute to neuronal homeostasis, robustness, and stress resistance. We found that the activity of the voltage-gated potassium channel seizure (sei), an ortholog of the mammalian ERG channel family, is essential for protecting flies from acute heat-induced seizures. Although sei is broadly expressed in the nervous system, our data indicate that its impact on the organismal robustness to acute environmental stress is primarily mediated via its action in excitatory neurons, the octopaminergic system, as well as neuropile ensheathing and perineurial glia. Furthermore, our studies suggest that human mutations in the human ERG channel (hERG), which have been primarily implicated in the cardiac Long QT Syndrome (LQTS), may also contribute to the high incidence of seizures in LQTS patients via a cardiovascular-independent neurogenic pathway.
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Affiliation(s)
- Alexis S. Hill
- Department of Biology, College of the Holy Cross, Worcester, Massachusetts, United States of America
| | - Poorva Jain
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Nicole E. Folan
- Department of Biology, College of the Holy Cross, Worcester, Massachusetts, United States of America
| | - Yehuda Ben-Shahar
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, United States of America
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Kasuya J, Iyengar A, Chen HL, Lansdon P, Wu CF, Kitamoto T. Milk-whey diet substantially suppresses seizure-like phenotypes of paraShu, a Drosophila voltage-gated sodium channel mutant. J Neurogenet 2019; 33:164-178. [PMID: 31096839 DOI: 10.1080/01677063.2019.1597082] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The Drosophila mutant paraShu harbors a dominant, gain-of-function allele of the voltage-gated sodium channel gene, paralytic (para). The mutant flies display severe seizure-like phenotypes, including neuronal hyperexcitability, spontaneous spasms, ether-induced leg shaking, and heat-induced convulsions. We unexpectedly found that two distinct food recipes used routinely in the Drosophila research community result in a striking difference in severity of the paraShu phenotypes. Namely, when paraShu mutants were raised on the diet originally formulated by Edward Lewis in 1960, they showed severe neurological defects as previously reported. In contrast, when they were raised on the diet developed by Frankel and Brousseau in 1968, these phenotypes were substantially suppressed. Comparison of the effects of these two well-established food recipes revealed that the diet-dependent phenotypic suppression is accounted for by milk whey, which is present only in the latter. Inclusion of milk whey in the diet during larval stages was critical for suppression of the adult paraShu phenotypes, suggesting that this dietary modification affects development of the nervous system. We also found that milk whey has selective effects on other neurological mutants. Among the behavioral phenotypes of different para mutant alleles, those of paraGEFS+ and parabss were suppressed by milk whey, while those of paraDS and parats1 were not significantly affected. Overall, our study demonstrates that different diets routinely used in Drosophila labs could have considerably different effects on neurological phenotypes of Drosophila mutants. This finding provides a solid foundation for further investigation into how dietary modifications affect development and function of the nervous system and, ultimately, how they influence behavior.
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Affiliation(s)
- Junko Kasuya
- a Department of Anesthesia, Carver College of Medicine , University of Iowa , Iowa city , IA , USA
| | - Atulya Iyengar
- b Department of Biology, College of Liberal Arts and Sciences , University of Iowa , Iowa city , IA , USA.,c Interdisciplinary Graduate Program in Neuroscience , University of Iowa , Iowa city , IA , USA
| | - Hung-Lin Chen
- d Department of Medical Research , Tung's Taichung MetroHarbor Hospital , Taichung , Taiwan 43503 , ROC
| | - Patrick Lansdon
- e Interdisciplinary Graduate Program in Genetics , University of Iowa , Iowa city , IA , USA
| | - Chun-Fang Wu
- b Department of Biology, College of Liberal Arts and Sciences , University of Iowa , Iowa city , IA , USA.,c Interdisciplinary Graduate Program in Neuroscience , University of Iowa , Iowa city , IA , USA.,e Interdisciplinary Graduate Program in Genetics , University of Iowa , Iowa city , IA , USA
| | - Toshihiro Kitamoto
- a Department of Anesthesia, Carver College of Medicine , University of Iowa , Iowa city , IA , USA.,c Interdisciplinary Graduate Program in Neuroscience , University of Iowa , Iowa city , IA , USA.,e Interdisciplinary Graduate Program in Genetics , University of Iowa , Iowa city , IA , USA
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Lee J, Iyengar A, Wu CF. Distinctions among electroconvulsion- and proconvulsant-induced seizure discharges and native motor patterns during flight and grooming: quantitative spike pattern analysis in Drosophila flight muscles. J Neurogenet 2019; 33:125-142. [PMID: 30982417 DOI: 10.1080/01677063.2019.1581188] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In Drosophila, high-frequency electrical stimulation across the brain triggers a highly stereotypic repertoire of spasms. These electroconvulsive seizures (ECS) manifest as distinctive spiking discharges across the nervous system and can be stably assessed throughout the seizure repertoire in the large indirect flight muscles dorsal longitudinal muscles (DLMs) to characterize modifications in seizure-prone mutants. However, the relationships between ECS-spike patterns and native motor programs, including flight and grooming, are not known and their similarities and distinctions remain to be characterized. We employed quantitative spike pattern analyses for the three motor patterns including: (1) overall firing frequency, (2) spike timing between contralateral fibers, and (3) short-term variability in spike interval regularity (CV2) and instantaneous firing frequency (ISI-1). This base-line information from wild-type (WT) flies facilitated quantitative characterization of mutational effects of major neurotransmitter systems: excitatory cholinergic (Cha), inhibitory GABAergic (Rdl) and electrical (ShakB) synaptic transmission. The results provide an initial glimpse on the vulnerability of individual motor patterns to different perturbations. We found marked alterations of ECS discharge spike patterns in terms of either seizure threshold, spike frequency or spiking regularity. In contrast, no gross alterations during grooming and a small but noticeable reduction of firing frequency during Rdl mutant flight were found, suggesting a role for GABAergic modulation of flight motor programs. Picrotoxin (PTX), a known pro-convulsant that inhibits GABAA receptors, induced DLM spike patterns that displayed some features, e.g. left-right coordination and ISI-1 range, that could be found in flight or grooming, but distinct from ECS discharges. These quantitative techniques may be employed to reveal overlooked relationships among aberrant motor patterns as well as their links to native motor programs.
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Affiliation(s)
- Jisue Lee
- a Department of Biology , University of Iowa , Iowa City , IA , USA
| | - Atulya Iyengar
- a Department of Biology , University of Iowa , Iowa City , IA , USA.,b Interdisiplinary Graduate Program in Neuroscience , University of Iowa , Iowa City , IA , USA
| | - Chun-Fang Wu
- a Department of Biology , University of Iowa , Iowa City , IA , USA.,b Interdisiplinary Graduate Program in Neuroscience , University of Iowa , Iowa City , IA , USA
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Unraveling Synaptic GCaMP Signals: Differential Excitability and Clearance Mechanisms Underlying Distinct Ca 2+ Dynamics in Tonic and Phasic Excitatory, and Aminergic Modulatory Motor Terminals in Drosophila. eNeuro 2018; 5:eN-NWR-0362-17. [PMID: 29464198 PMCID: PMC5818553 DOI: 10.1523/eneuro.0362-17.2018] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 01/27/2018] [Accepted: 02/02/2018] [Indexed: 11/21/2022] Open
Abstract
GCaMP is an optogenetic Ca2+ sensor widely used for monitoring neuronal activities but the precise physiological implications of GCaMP signals remain to be further delineated among functionally distinct synapses. The Drosophila neuromuscular junction (NMJ), a powerful genetic system for studying synaptic function and plasticity, consists of tonic and phasic glutamatergic and modulatory aminergic motor terminals of distinct properties. We report a first simultaneous imaging and electric recording study to directly contrast the frequency characteristics of GCaMP signals of the three synapses for physiological implications. Different GCaMP variants were applied in genetic and pharmacological perturbation experiments to examine the Ca2+ influx and clearance processes underlying the GCaMP signal. Distinct mutational and drug effects on GCaMP signals indicate differential roles of Na+ and K+ channels, encoded by genes including paralytic (para), Shaker (Sh), Shab, and ether-a-go-go (eag), in excitability control of different motor terminals. Moreover, the Ca2+ handling properties reflected by the characteristic frequency dependence of the synaptic GCaMP signals were determined to a large extent by differential capacity of mitochondria-powered Ca2+ clearance mechanisms. Simultaneous focal recordings of synaptic activities further revealed that GCaMPs were ineffective in tracking the rapid dynamics of Ca2+ influx that triggers transmitter release, especially during low-frequency activities, but more adequately reflected cytosolic residual Ca2+ accumulation, a major factor governing activity-dependent synaptic plasticity. These results highlight the vast range of GCaMP response patterns in functionally distinct synaptic types and provide relevant information for establishing basic guidelines for the physiological interpretations of presynaptic GCaMP signals from in situ imaging studies.
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Lithium-Responsive Seizure-Like Hyperexcitability Is Caused by a Mutation in the Drosophila Voltage-Gated Sodium Channel Gene paralytic. eNeuro 2016; 3:eN-NWR-0221-16. [PMID: 27844061 PMCID: PMC5103163 DOI: 10.1523/eneuro.0221-16.2016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 10/06/2016] [Indexed: 01/01/2023] Open
Abstract
Shudderer (Shu) is an X-linked dominant mutation in Drosophila melanogaster identified more than 40 years ago. A previous study showed that Shu caused spontaneous tremors and defects in reactive climbing behavior, and that these phenotypes were significantly suppressed when mutants were fed food containing lithium, a mood stabilizer used in the treatment of bipolar disorder (Williamson, 1982). This unique observation suggested that the Shu mutation affects genes involved in lithium-responsive neurobiological processes. In the present study, we identified Shu as a novel mutant allele of the voltage-gated sodium (Nav) channel gene paralytic (para). Given that hypomorphic para alleles and RNA interference-mediated para knockdown reduced the severity of Shu phenotypes, Shu was classified as a para hypermorphic allele. We also demonstrated that lithium could improve the behavioral abnormalities displayed by other Nav mutants, including a fly model of the human generalized epilepsy with febrile seizures plus. Our electrophysiological analysis of Shu showed that lithium treatment did not acutely suppress Nav channel activity, indicating that the rescue effect of lithium resulted from chronic physiological adjustments to this drug. Microarray analysis revealed that lithium significantly alters the expression of various genes in Shu, including those involved in innate immune responses, amino acid metabolism, and oxidation-reduction processes, raising the interesting possibility that lithium-induced modulation of these biological pathways may contribute to such adjustments. Overall, our findings demonstrate that Nav channel mutants in Drosophila are valuable genetic tools for elucidating the effects of lithium on the nervous system in the context of neurophysiology and behavior.
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Seizure Suppression by High Temperature via cAMP Modulation in Drosophila. G3-GENES GENOMES GENETICS 2016; 6:3381-3387. [PMID: 27558668 PMCID: PMC5068957 DOI: 10.1534/g3.116.034629] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Bang-sensitive (BS) Drosophila mutants display characteristic seizure-like activity (SLA) and paralysis after mechanical shock . After high-frequency electrical stimulation (HFS) of the brain, they generate robust seizures at very low threshold voltage. Here we report an important phenomenon, which effectively suppresses SLA in BS mutants. High temperature causes seizure suppression in all BS mutants (parabss1, eas, sda) examined in this study. This effect is fully reversible and flies show complete recovery from BS paralysis once the temperature effect is nullified. High temperature induces an increase in seizure threshold after a brief pulse of heat shock (HS). By genetic screening, we identified the involvement of cAMP in the suppression of seizures by high temperature. We propose that HS induces adenylyl cyclase which in turn increases cAMP concentration which eventually suppresses seizures in mutant flies. In summary, we describe an unusual phenomenon, where high temperature can suppress SLA in flies by modulating cAMP concentration.
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Ehaideb SN, Wignall EA, Kasuya J, Evans WH, Iyengar A, Koerselman HL, Lilienthal AJ, Bassuk AG, Kitamoto T, Manak JR. Mutation of orthologous prickle genes causes a similar epilepsy syndrome in flies and humans. Ann Clin Transl Neurol 2016; 3:695-707. [PMID: 27648459 PMCID: PMC5018582 DOI: 10.1002/acn3.334] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 06/24/2016] [Accepted: 06/27/2016] [Indexed: 11/09/2022] Open
Abstract
OBJECTIVE Genetically tractable fruit flies have been used for decades to study seizure disorders. However, there is a paucity of data specifically correlating fly and human seizure phenotypes. We have previously shown that mutation of orthologous PRICKLE genes from flies to humans produce seizures. This study aimed to determine whether the prickle-mediated seizure phenotypes in flies closely parallel the epilepsy syndrome found in PRICKLE patients. METHODS Virtually all fly seizure studies have relied upon characterizing seizures that are evoked. We have developed two novel approaches to more precisely characterize seizure-related phenotypes in their native state in prickle mutant flies. First, we used high-resolution videography to document spontaneous, unprovoked seizure events. Second, we developed a locomotion coordination assay to assess whether the prickle mutant flies were ataxic. Third, we treated the mutant flies with levetiracetam to determine whether the behavioral phenotypes could be suppressed by a common antiepileptic drug. RESULTS We find that the prickle mutant flies exhibit myoclonic-like spontaneous seizure events and are severely ataxic. Both these phenotypes are found in human patients with PRICKLE mutations, and can be suppressed by levetiracetam, providing evidence that the phenotypes are due to neurological dysfunction. These results document for the first time spontaneous, unprovoked seizure events at high resolution in a fly human seizure disorder model, capturing seizures in their native state. INTERPRETATION Collectively, these data underscore the striking similarities between the fly and human PRICKLE-mediated epilepsy syndromes, and provide a genetically tractable model for dissecting the underlying causes of the human syndromic phenotypes.
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Affiliation(s)
- Salleh N Ehaideb
- Interdisciplinary Graduate Program in Genetics University of Iowa Iowa City Iowa; King Abdullah International Medical Research Cente rKing Abdulaziz Medical City Riyadh Saudi Arabia; Department of Biology University of Iowa Iowa City Iowa
| | | | - Junko Kasuya
- Department of Anesthesia University of Iowa Iowa City Iowa
| | | | - Atulya Iyengar
- Department of Biology University of Iowa Iowa City Iowa; Interdisciplinary Graduate Program in Neuroscience University of Iowa Iowa City Iowa
| | | | | | | | - Toshihiro Kitamoto
- Interdisciplinary Graduate Program in Genetics University of Iowa Iowa City Iowa; Department of Anesthesia University of Iowa Iowa City Iowa; Interdisciplinary Graduate Program in Neuroscience University of Iowa Iowa City Iowa
| | - J Robert Manak
- Interdisciplinary Graduate Program in Genetics University of Iowa Iowa City Iowa; Department of Biology University of Iowa Iowa City Iowa; Interdisciplinary Graduate Program in Neuroscience University of Iowa Iowa City Iowa; Department of Pediatrics University of Iowa Iowa City Iowa
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Kroll JR, Saras A, Tanouye MA. Drosophila sodium channel mutations: Contributions to seizure-susceptibility. Exp Neurol 2015; 274:80-7. [PMID: 26093037 DOI: 10.1016/j.expneurol.2015.06.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Revised: 06/14/2015] [Accepted: 06/16/2015] [Indexed: 01/10/2023]
Abstract
This paper reviews Drosophila voltage-gated Na(+) channel mutations encoded by the para (paralytic) gene and their contributions to seizure disorders in the fly. Numerous mutations cause seizure-sensitivity, for example, para(bss1), with phenotypes that resemble human intractable epilepsy in some aspects. Seizure phenotypes are also seen with human GEFS+ spectrum mutations that have been knocked into the Drosophila para gene, para(GEFS+) and para(DS) alleles. Other para mutations, para(ST76) and para(JS) act as seizure-suppressor mutations reverting seizure phenotypes in other mutants. Seizure-like phenotypes are observed from mutations and other conditions that cause a persistent Na(+) current through either changes in mRNA splicing or protein structure.
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Affiliation(s)
- Jason R Kroll
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Arunesh Saras
- Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720, USA
| | - Mark A Tanouye
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA; Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720, USA.
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Iyengar A, Wu CF. Flight and seizure motor patterns in Drosophila mutants: simultaneous acoustic and electrophysiological recordings of wing beats and flight muscle activity. J Neurogenet 2014; 28:316-28. [PMID: 25159538 PMCID: PMC5555410 DOI: 10.3109/01677063.2014.957827] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Abstract Tethered flies allow studies of biomechanics and electrophysiology of flight control. We performed microelectrode recordings of spikes in an indirect flight muscle (the dorsal longitudinal muscle, DLMa) coupled with acoustic analysis of wing beat frequency (WBF) via microphone signals. Simultaneous electrophysiological recording of direct and indirect flight muscles has been technically challenging; however, the WBF is thought to reflect in a one-to-one relationship with spiking activity in a subset of direct flight muscles, including muscle m1b. Therefore, our approach enables systematic mutational analysis for changes in temporal features of electrical activity of motor neurons innervating subsets of direct and indirect flight muscles. Here, we report the consequences of specific ion channel disruptions on the spiking activity of myogenic DLMs (firing at ∼5 Hz) and the corresponding WBF (∼200 Hz). We examined mutants of the genes enconding: 1) voltage-gated Ca(2+) channels (cacophony, cac), 2) Ca(2+)-activated K(+) channels (slowpoke, slo), and 3) voltage-gated K(+) channels (Shaker, Sh) and their auxiliary subunits (Hyperkinetic, Hk and quiver, qvr). We found flight initiation in response to an air puff was severely disrupted in both cac and slo mutants. However, once initiated, slo flight was largely unaltered, whereas cac displayed disrupted DLM firing rates and WBF. Sh, Hk, and qvr mutants were able to maintain normal DLM firing rates, despite increased WBF. Notably, defects in the auxiliary subunits encoded by Hk and qvr could lead to distinct consequences, that is, disrupted DLM firing rhythmicity, not observed in Sh. Our mutant analysis of direct and indirect flight muscle activities indicates that the two motor activity patterns may be independently modified by specific ion channel mutations, and that this approach can be extended to other dipteran species and additional motor programs, such as electroconvulsive stimulation-induced seizures.
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Affiliation(s)
- Atulya Iyengar
- Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, IA 52242, USA
| | - Chun-Fang Wu
- Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, IA 52242, USA
- Department of Biology, University of Iowa, Iowa City, IA 52242, USA
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Ehaideb SN, Iyengar A, Ueda A, Iacobucci GJ, Cranston C, Bassuk AG, Gubb D, Axelrod JD, Gunawardena S, Wu CF, Manak JR. prickle modulates microtubule polarity and axonal transport to ameliorate seizures in flies. Proc Natl Acad Sci U S A 2014; 111:11187-92. [PMID: 25024231 PMCID: PMC4121842 DOI: 10.1073/pnas.1403357111] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Recent analyses in flies, mice, zebrafish, and humans showed that mutations in prickle orthologs result in epileptic phenotypes, although the mechanism responsible for generating the seizures was unknown. Here, we show that Prickle organizes microtubule polarity and affects their growth dynamics in axons of Drosophila neurons, which in turn influences both anterograde and retrograde vesicle transport. We also show that enhancement of the anterograde transport mechanism is the cause of the seizure phenotype in flies, which can be suppressed by reducing the level of either of two Kinesin motor proteins responsible for anterograde vesicle transport. Additionally, we show that seizure-prone prickle mutant flies have electrophysiological defects similar to other fly mutants used to study seizures, and that merely altering the balance of the two adult prickle isoforms in neurons can predispose flies to seizures. These data reveal a previously unidentified pathway in the pathophysiology of seizure disorders and provide evidence for a more generalized cellular mechanism whereby Prickle mediates polarity by influencing microtubule-mediated transport.
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Affiliation(s)
- Salleh N Ehaideb
- Interdisciplinary Graduate Programs in Genetics,King Abdullah International Medical Research Center, King Abdulaziz Medical City, Riyadh 11426, Kingdom of Saudi Arabia
| | | | | | - Gary J Iacobucci
- Department of Biological Sciences, University at Buffalo, The State University of New York, Buffalo, NY 14260
| | | | | | - David Gubb
- Reponse Immunitaire et Developpment, Centre National de la Recherche Scientifique, 67084 Strasbourg Cedex, France; and
| | - Jeffrey D Axelrod
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305
| | - Shermali Gunawardena
- Department of Biological Sciences, University at Buffalo, The State University of New York, Buffalo, NY 14260
| | - Chun-Fang Wu
- Interdisciplinary Graduate Programs in Genetics,Neuroscience, andDepartments of Biology and
| | - J Robert Manak
- Interdisciplinary Graduate Programs in Genetics,Departments of Biology andPediatrics, University of Iowa, Iowa City, IA 52242;
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Rusan ZM, Kingsford OA, Tanouye MA. Modeling glial contributions to seizures and epileptogenesis: cation-chloride cotransporters in Drosophila melanogaster. PLoS One 2014; 9:e101117. [PMID: 24971529 PMCID: PMC4074161 DOI: 10.1371/journal.pone.0101117] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2014] [Accepted: 06/03/2014] [Indexed: 12/21/2022] Open
Abstract
Flies carrying a kcc loss-of-function mutation are more seizure-susceptible than wild-type flies. The kcc gene is the highly conserved Drosophila melanogaster ortholog of K+/Cl- cotransporter genes thought to be expressed in all animal cell types. Here, we examined the spatial and temporal requirements for kcc loss-of-function to modify seizure-susceptibility in flies. Targeted RNA interference (RNAi) of kcc in various sets of neurons was sufficient to induce severe seizure-sensitivity. Interestingly, kcc RNAi in glia was particularly effective in causing seizure-sensitivity. Knockdown of kcc in glia or neurons during development caused a reduction in seizure induction threshold, cell swelling, and brain volume increase in 24-48 hour old adult flies. Third instar larval peripheral nerves were enlarged when kcc RNAi was expressed in neurons or glia. Results suggest that a threshold of K+/Cl- cotransport dysfunction in the nervous system during development is an important determinant of seizure-susceptibility in Drosophila. The findings presented are the first attributing a causative role for glial cation-chloride cotransporters in seizures and epileptogenesis. The importance of elucidating glial cell contributions to seizure disorders and the utility of Drosophila models is discussed.
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Affiliation(s)
- Zeid M. Rusan
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Olivia A. Kingsford
- Department of Environmental Science, Policy and Management, University of California, Berkeley, California, United States of America
| | - Mark A. Tanouye
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
- Department of Environmental Science, Policy and Management, University of California, Berkeley, California, United States of America
- Helen Wills Neuroscience Institute, University of California, Berkeley, California, United States of America
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Kroll JR, Tanouye MA. Rescue of easily shocked mutant seizure sensitivity in Drosophila adults. J Comp Neurol 2014; 521:3500-7. [PMID: 23682034 DOI: 10.1002/cne.23364] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Revised: 05/03/2013] [Accepted: 05/03/2013] [Indexed: 11/08/2022]
Abstract
Genetic factors that influence seizure susceptibility can act transiently during the development of neural circuits or might be necessary for the proper functioning of existing circuits. We provide evidence that the Drosophila seizure-sensitive mutant easily shocked (eas) represents a neurological disorder in which abnormal functioning of existing neural circuits leads to seizure sensitivity. The eas(+) gene encodes for the protein Ethanolamine Kinase, involved in phospholipid biosynthesis. We show that induction of eas(+) in adult mutant flies rescues them from seizure sensitivity despite previously known developmental defects in brain morphology. Additionally, through cell-type-specific rescue, our results suggest a specific role for eas(+) in excitatory rather than inhibitory neural transmission. Overall, our findings emphasize an important role for proper phospholipid metabolism in normal brain function and suggest that certain classes of epilepsy syndromes could have the potential to be treated with gene therapy techniques.
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Affiliation(s)
- Jason R Kroll
- Division of Neurobiology, Department of Molecular and Cell Biology, University of California, Berkeley, CA, 94720
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Burg MG, Wu CF. Mechanical and temperature stressor-induced seizure-and-paralysis behaviors in Drosophila bang-sensitive mutants. J Neurogenet 2012; 26:189-97. [PMID: 22716921 DOI: 10.3109/01677063.2012.690011] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
"Bang-sensitive" mutants of Drosophila display characteristic repertoires of distinct seizure-and-paralysis behaviors upon mechanical shock (Ganetzky & Wu, 1982, Genetics, 100, 597-614). The authors found that each of the bang-sensitive mutants described in this paper (bas, bss, eas, and tko) also displayed similar behavioral repertoires upon exposure to either high or low temperature. These repertoires are composed of interspersed periods of seizure and paralysis, and appear to have interesting parallels with vertebrate epileptiform behavior. Analysis of gynandromorph mosaics of these bang-sensitive mutant flies indicated that anatomical foci required for these two types of behaviors do not totally overlap, as they were separable among mosaic flies. Observations on mosaic and decapitated flies demonstrated an all-or-none expression of the seizure-and-paralysis behaviors, indicating global activity and long-range interactions in the nervous system. Therefore, the diverse collection of currently available Drosophila bang-sensitive mutants may serve as a rich source for mutational and cellular analysis to identify interacting molecular networks that are responsible for seizure phenotypes.
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Affiliation(s)
- Martin G Burg
- PhD Program in Genetics and Department of Biology, University of Iowa, Iowa City, IA, USA.
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Ueda A, Grabbe C, Lee J, Lee J, Palmer RH, Wu CF. Mutation of Drosophila focal adhesion kinase induces bang-sensitive behavior and disrupts glial function, axonal conduction and synaptic transmission. Eur J Neurosci 2008; 27:2860-70. [PMID: 18540882 DOI: 10.1111/j.1460-9568.2008.06252.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The role of the conserved focal adhesion kinase (FAK) family of protein tyrosine kinases in the development and physiological functions of the CNS has long been an area of interest among neuroscientists. In this report, we observe that Drosophila mutants lacking Fak56 exhibit a decreased lifespan, accompanied by a bang-sensitive phenotype, which is characterized by sensitivity to mechanical and high-frequency electrical stimulation. Fak56 mutant animals display lower thresholds and higher rates of seizures in response to electroconvulsive stimuli. Direct measurements of action potential conduction in larval segmental nerves demonstrate a slowed propagation speed and failure during high-frequency nerve stimulation. In addition, neuromuscular junctions in Fak56 mutant animals display transmission blockade during high-frequency activity as a result of action potential failure. Endogenous Fak56 protein is abundant in glial cells ensheathing the axon bundles, and structural alterations of segmental nerve bundles can be observed in mutants. Manipulation of Fak56 function specifically in glial cells also disrupts action potential conduction and neurotransmission, suggesting a glial component in the Fak56 bang-sensitive phenotype. Furthermore, we show that increased intracellular calcium levels result in the dephosphorylation of endogenous Fak56 protein in Drosophila cell lines, in parallel with our observations of highly variable synaptic potentials at a higher Ca2+ level in Fak56 mutant larvae. Together these findings suggest that modulation of Fak56 function is important for action potential propagation and Ca2+-regulated neuromuscular transmission in vivo.
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Affiliation(s)
- Atsushi Ueda
- Department of Biological Sciences, University of Iowa, Iowa City, IA 52242, USA
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Abstract
PURPOSE OF REVIEW Animal models provide a means to investigate fundamental mechanisms of abnormal electrical discharge (i.e., seizures). Understanding the pathogenesis of epilepsy and therapy development have greatly benefited from these models. Here we review recent mouse mutants featuring spontaneous seizures and simpler organisms. RECENT FINDINGS New genetically engineered mice provide additional insights to cellular mechanisms underlying seizure generation (BK calcium-activated potassium channels and interneuron-expressed sodium channels), genetic interactions that exacerbate seizure phenotype (Scn2a, Kcnq2 and background) and neurodevelopmental influences (Dlx transcription factors). Mutants for neuronal nicotinic acetylcholine receptors, Glut-1 deficiency and aquaporin channels highlight additional seizure phenotypes in mice. Additional models in Caenorhabditis elegans (Lis-1) and Danio rerio (pentylenetetrazole) highlight a reductionist approach. Taking further advantage of 'simple' organisms, antiepileptic drugs and genetic modifiers of seizure activity are being uncovered in Drosophila. SUMMARY Studies of epilepsy in mutant mice provide a framework for understanding critical features of the brain that regulate excitability. These, and as yet undiscovered, mouse mutants will continue to serve as the foundation for basic epilepsy research. Interestingly, an even greater potential for analyzing epileptic phenotypes may lie in the more widespread use of genetically tractable organisms such as worms, flies and zebrafish.
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Affiliation(s)
- Scott C Baraban
- Epilepsy Research Laboratory, Department of Neurological Surgery, University of California, San Francisco, CA 94143, USA.
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Peng IF, Wu CF. Differential contributions of Shaker and Shab K+ currents to neuronal firing patterns in Drosophila. J Neurophysiol 2006; 97:780-94. [PMID: 17079336 DOI: 10.1152/jn.01012.2006] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Different K(+) currents participate in generating neuronal firing patterns. The Drosophila embryonic "giant" neuron culture system has facilitated current- and voltage-clamp recordings to correlate distinct excitability patterns with the underlying K(+) currents and to delineate the mutational effects of identified K(+) channels. Mutations of Sh and Shab K(+) channels removed part of inactivating I(A) and sustained I(K), respectively, and the remaining I(A) and I(K) revealed the properties of their counterparts, e.g., Shal and Shaw channels. Neuronal subsets displaying the delayed, tonic, adaptive, and damping spike patterns were characterized by different profiles of K(+) current voltage dependence and kinetics and by differential mutational effects. Shab channels regulated membrane repolarization and repetitive firing over hundreds of milliseconds, and Shab neurons showed a gradual decline in repolarization during current injection and their spike activities became limited to high-frequency, damping firing. In contrast, Sh channels acted on events within tens of milliseconds, and Sh mutations broadened spikes and reduced firing rates without eliminating any categories of firing patterns. However, removing both Sh and Shal I(A) by 4-aminopyridine converted the delayed to damping firing pattern, demonstrating their actions in regulating spike initiation. Specific blockade of Shab I(K) by quinidine mimicked the Shab phenotypes and converted tonic firing to a damping pattern. These conversions suggest a hierarchy of complexity in K(+) current interactions underlying different firing patterns. Different lineage-defined neuronal subsets, identifiable by employing the GAL4-UAS system, displayed different profiles of spike properties and K(+) current compositions, providing opportunities for mutational analysis in functionally specialized neurons.
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Affiliation(s)
- I-Feng Peng
- Department of Biological Sciences, University of Iowa, Iowa City, IA 52242, USA
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