Publications by authors named "Levi P Sowers"

19 Publications

  • Page 1 of 1

Stimulation of CGRP-expressing neurons in the medial cerebellar nucleus induces light and touch sensitivity in mice.

Neurobiol Pain 2022 Aug-Dec;12:100098. Epub 2022 Jun 23.

Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA.

Calcitonin gene-related peptide (CGRP) is considered a major player in migraine pathophysiology. However, the location and mechanisms of CGRP actions in migraine are not clearly elucidated. One important question yet to be answered is: Does central CGRP signaling play a role in migraine? One candidate site is the cerebellum, which serves as a sensory and motor integration center and is activated in migraine patients. The cerebellum has the most CGRP binding sites in the central nervous system and a deep cerebellar nucleus, the medial nucleus (MN), expresses CGRP (MN). A previous study demonstrated that CGRP delivery into the cerebellum induced migraine-like behaviors. We hypothesized that stimulation of MN neurons might induce migraine-like behaviors. To test the hypothesis, we used an optogenetic strategy using mice to drive Cre-dependent expression of channelrhodopsin-2 selectively in CGRP neurons in the cerebellar MN. A battery of behavioral tests was done to assess preclinical behaviors that are surrogates of migraine symptoms, including light aversion, cutaneous allodynia, and spontaneous pain when MN neurons were optically stimulated. Motor functions were also assessed. Optical stimulation of MN neurons decreased the time spent in the light, which was coupled to increased time spent resting in the dark, but not the light. These changes were only significant in female mice. Plantar tactile sensitivity was increased in the ipsilateral paws of both sexes, but contralateral paw data were less clear. There was no significant increase in anxiety-like behavior, spontaneous pain (squint), or changes in gait. These discoveries reveal that MN neurons may contribute to migraine-like sensory hypersensitivity to light and touch.
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http://dx.doi.org/10.1016/j.ynpai.2022.100098DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9240374PMC
June 2022

CGRP Administration Into the Cerebellum Evokes Light Aversion, Tactile Hypersensitivity, and Nociceptive Squint in Mice.

Front Pain Res (Lausanne) 2022 25;3:861598. Epub 2022 Apr 25.

Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA, United States.

The neuropeptide calcitonin gene-related peptide (CGRP) is a major player in migraine pathophysiology. Previous preclinical studies demonstrated that intracerebroventricular administration of CGRP caused migraine-like behaviors in mice, but the sites of action in the brain remain unidentified. The cerebellum has the most CGRP binding sites in the central nervous system and is increasingly recognized as both a sensory and motor integration center. The objective of this study was to test whether the cerebellum, particularly the medial cerebellar nuclei (MN), might be a site of CGRP action. In this study, CGRP was directly injected into the right MN of C57BL/6J mice via a cannula. A battery of tests was done to assess preclinical behaviors that are surrogates of migraine-like symptoms. CGRP caused light aversion measured as decreased time in the light zone even with dim light. The mice also spent more time resting in the dark zone, but not the light, along with decreased rearing and transitions between zones. These behaviors were similar for both sexes. Moreover, significant responses to CGRP were seen in the open field assay, von Frey test, and automated squint assay, indicating anxiety, tactile hypersensitivity, and spontaneous pain, respectively. Interestingly, CGRP injection caused significant anxiety and spontaneous pain responses only in female mice, and a more robust tactile hypersensitivity in female mice. No detectable effect of CGRP on gait was observed in either sex. These results suggest that CGRP injection in the MN causes light aversion accompanied by increased anxiety, tactile hypersensitivity, and spontaneous pain. A caveat is that we cannot exclude contributions from other cerebellar regions in addition to the MN due to diffusion of the injected peptide. These results reveal the cerebellum as a new site of CGRP actions that may contribute to migraine-like hypersensitivity.
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http://dx.doi.org/10.3389/fpain.2022.861598DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9082264PMC
April 2022

Automated detection of squint as a sensitive assay of sex-dependent calcitonin gene-related peptide and amylin-induced pain in mice.

Pain 2022 08 10;163(8):1511-1519. Epub 2021 Nov 10.

Department of Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, IA, United States.

Abstract: We developed an automated squint assay using both black C57BL/6J and white CD1 mice to measure the interpalpebral fissure area between the upper and lower eyelids as an objective quantification of pain. The automated software detected a squint response to the commonly used nociceptive stimulus formalin in C57BL/6J mice. After this validation, we used the automated assay to detect a dose-dependent squint response to a migraine trigger, the neuropeptide calcitonin gene-related peptide, including a response in female mice at a dose below detection by the manual grimace scale. Finally, we found that the calcitonin gene-related peptide amylin induced squinting behavior in female mice, but not males. These data demonstrate that an automated squint assay can be used as an objective, real-time, continuous-scale measure of pain that provides higher precision and real-time analysis compared with manual grimace assessments.
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http://dx.doi.org/10.1097/j.pain.0000000000002537DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9085964PMC
August 2022

Investigating Migraine-Like Behavior using Light Aversion in Mice.

J Vis Exp 2021 08 11(174). Epub 2021 Aug 11.

Center for the Prevention and Treatment of Visual Loss, Veterans Administration Health Center, Iowa City, IA; Department of Molecular Physiology and Biophysics, University of Iowa; Department of Neurology, University of Iowa;

Migraine is a complex neurological disorder characterized by headache and sensory abnormalities, such as hypersensitivity to light, observed as photophobia. Whilst it is impossible to confirm that a mouse is experiencing migraine, light aversion can be used as a behavioral surrogate for the migraine symptom of photophobia. To test for light aversion, we utilize the light/dark assay to measure the time mice freely choose to spend in either a light or dark environment. The assay has been refined by introducing two critical modifications: pre-exposures to the chamber prior to running the test procedure and adjustable chamber lighting, permitting the use of a range of light intensities from 55 lux to 27,000 lux. Because the choice to spend more time in the dark is also indicative of anxiety, we also utilize a light-independent anxiety test, the open field assay, to distinguish anxiety from light-aversive behavior. Here, we describe a modified test paradigm for the light/dark and open field assays. The application of these assays is described for intraperitoneal injection of calcitonin gene-related peptide (CGRP) in two mouse strains and for optogenetic brain stimulation studies.
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http://dx.doi.org/10.3791/62839DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8428768PMC
August 2021

PACAP Induces Light Aversion in Mice by an Inheritable Mechanism Independent of CGRP.

J Neurosci 2021 05 12;41(21):4697-4715. Epub 2021 Apr 12.

Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242

The neuropeptides CGRP (calcitonin gene-related peptide) and PACAP (pituitary adenylate cyclase-activating polypeptide) have emerged as mediators of migraine, yet the potential overlap of their mechanisms remains unknown. Infusion of PACAP, like CGRP, can cause migraine in people, and both peptides share similar vasodilatory and nociceptive functions. In this study, we have used light aversion in mice as a surrogate for migraine-like photophobia to compare CGRP and PACAP and ask whether CGRP or PACAP actions were dependent on each other. Similar to CGRP, PACAP induced light aversion in outbred CD-1 mice. The light aversion was accompanied by increased resting in the dark, but not anxiety in a light-independent open field assay. Unexpectedly, about one-third of the CD-1 mice did not respond to PACAP, which was not seen with CGRP. The responder and nonresponder phenotypes were stable, inheritable, and not sex linked, although there was a trend for greater responses among male mice. RNA-sequencing analysis of trigeminal ganglia yielded hierarchical clustering of responder and nonresponder mice and revealed a number of candidate genes, including greater expression of the and ion channels and glycoprotein hormones and receptors in a subset of male responder mice. Importantly, an anti-PACAP monoclonal antibody could block PACAP-induced light aversion but not CGRP-induced light aversion. Conversely, an anti-CGRP antibody could not block PACAP-induced light aversion. Thus, we propose that CGRP and PACAP act by independent convergent pathways that cause a migraine-like symptom in mice. The relationship between the neuropeptides CGRP (calcitonin gene-related peptide) and PACAP (pituitary adenylate cyclase-activating polypeptide) in migraine is relevant given that both peptides can induce migraine in people, yet to date only drugs that target CGRP are available. Using an outbred strain of mice, we were able to show that most, but not all, mice respond to PACAP in a preclinical photophobia assay. Our finding that CGRP and PACAP monoclonal antibodies do not cross-inhibit the other peptide indicates that CGRP and PACAP actions are independent and suggests that PACAP-targeted drugs may be effective in patients who do not respond to CGRP-based therapeutics.
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http://dx.doi.org/10.1523/JNEUROSCI.2200-20.2021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8260237PMC
May 2021

Amylin Analog Pramlintide Induces Migraine-like Attacks in Patients.

Ann Neurol 2021 06 8;89(6):1157-1171. Epub 2021 Apr 8.

Department of Neurology, Danish Headache Center, Rigshospitalet Glostrup, Faculty of Health and Medical Sciences, University of Copenhagen, Glostrup, Denmark.

Objective: Migraine is a prevalent and disabling neurological disease. Its genesis is poorly understood, and there remains unmet clinical need. We aimed to identify mechanisms and thus novel therapeutic targets for migraine using human models of migraine and translational models in animals, with emphasis on amylin, a close relative of calcitonin gene-related peptide (CGRP).

Methods: Thirty-six migraine without aura patients were enrolled in a randomized, double-blind, 2-way, crossover, positive-controlled clinical trial study to receive infusion of an amylin analogue pramlintide or human αCGRP on 2 different experimental days. Furthermore, translational studies in cells and mouse models, and rat, mouse and human tissue samples were conducted.

Results: Thirty patients (88%) developed headache after pramlintide infusion, compared to 33 (97%) after CGRP (p = 0.375). Fourteen patients (41%) developed migraine-like attacks after pramlintide infusion, compared to 19 patients (56%) after CGRP (p = 0.180). The pramlintide-induced migraine-like attacks had similar clinical characteristics to those induced by CGRP. There were differences between treatments in vascular parameters. Human receptor pharmacology studies showed that an amylin receptor likely mediates these pramlintide-provoked effects, rather than the canonical CGRP receptor. Supporting this, preclinical experiments investigating symptoms associated with migraine showed that amylin treatment, like CGRP, caused cutaneous hypersensitivity and light aversion in mice.

Interpretation: Our findings propose amylin receptor agonism as a novel contributor to migraine pathogenesis. Greater therapeutic gains could therefore be made for migraine patients through dual amylin and CGRP receptor antagonism, rather than selectively targeting the canonical CGRP receptor. ANN NEUROL 2021;89:1157-1171.
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http://dx.doi.org/10.1002/ana.26072DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8486152PMC
June 2021

Different forms of traumatic brain injuries cause different tactile hypersensitivity profiles.

Pain 2021 04;162(4):1163-1175

Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA, United States.

Abstract: Chronic complications of traumatic brain injury represent one of the greatest financial burdens and sources of suffering in the society today. A substantial number of these patients suffer from posttraumatic headache (PTH), which is typically associated with tactile allodynia. Unfortunately, this phenomenon has been understudied, in large part because of the lack of well-characterized laboratory animal models. We have addressed this gap in the field by characterizing the tactile sensory profile of 2 nonpenetrating models of PTH. We show that multimodal traumatic brain injury, administered by a jet-flow overpressure chamber that delivers a severe compressive impulse accompanied by a variable shock front and acceleration-deceleration insult, produces long-term tactile hypersensitivity and widespread sensitization. These are phenotypes reminiscent of PTH in patients, in both cephalic and extracephalic regions. By contrast, closed head injury induces only transient cephalic tactile hypersensitivity, with no extracephalic consequences. Both models show a more severe phenotype with repetitive daily injury for 3 days, compared with either 1 or 3 successive injuries in a single day, providing new insight into patterns of injury that may place patients at a greater risk of developing PTH. After recovery from transient cephalic tactile hypersensitivity, mice subjected to closed head injury demonstrate persistent hypersensitivity to established migraine triggers, including calcitonin gene-related peptide and sodium nitroprusside, a nitric oxide donor. Our results offer the field new tools for studying PTH and preclinical support for a pathophysiologic role of calcitonin gene-related peptide in this condition.
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http://dx.doi.org/10.1097/j.pain.0000000000002103DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8008742PMC
April 2021

Stimulation of Posterior Thalamic Nuclei Induces Photophobic Behavior in Mice.

Headache 2020 Oct 4;60(9):1961-1981. Epub 2020 Aug 4.

Center for the Prevention and Treatment of Visual Loss, Iowa City, IA, USA.

Objective: A hallmark of migraine is photophobia. In mice, photophobia-like behavior is induced by calcitonin gene-related peptide (CGRP), a neuropeptide known to be a key player in migraine. In this study, we sought to identify sites within the brain from which CGRP could induce photophobia.

Design: We focused on the posterior thalamic region, which contains neurons responsive to both light and dural stimulation and has CGRP binding sites. We probed this area with both optogenetic stimulation and acute CGRP injections in wild-type mice. Since the light/dark assay has historically been used to investigate anxiety-like responses in animals, we measured anxiety in a light-independent open field assay and asked if stimulation of a brain region, the periaqueductal gray, that induces anxiety would yield similar results to posterior thalamic stimulation. The hippocampus was used as an anatomical control to ensure that light-aversive behaviors could not be induced by the stimulation of any brain region.

Results: Optogenetic activation of neuronal cell bodies in the posterior thalamic nuclei elicited light aversion in both bright and dim light without an anxiety-like response in an open field assay. Injection of CGRP into the posterior thalamic region triggered similar light-aversive behavior without anxiety. In contrast to the posterior thalamic nuclei, optogenetic stimulation of dorsal periaqueductal gray cell bodies caused both light aversion and an anxiety-like response, while CGRP injection had no effect. In the dorsal hippocampus, neither optical stimulation nor CGRP injection affected light aversion or open field behaviors.

Conclusion: Stimulation of posterior thalamic nuclei is able to initiate light-aversive signals in mice that may be modulated by CGRP to cause photophobia in migraine.
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http://dx.doi.org/10.1111/head.13917DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7604789PMC
October 2020

Patients With Vestibular Migraine are More Likely to Have Occipital Headaches than those With Migraine Without Vestibular Symptoms.

Headache 2020 Sep 25;60(8):1581-1591. Epub 2020 Jul 25.

Department of Neurology, University of Iowa, Iowa City, IA, USA.

Objective: To determine whether patients with vestibular migraine are more likely to suffer from an occipital headache than patients with migraine without vestibular symptoms.

Background: Vestibular migraine is an underdiagnosed disorder in which migraine is associated with vestibular symptoms. Anatomical evidence and symptomatology hint at the involvement of brain structures in the posterior fossa (back of the head location). We hypothesized that vestibular migraine patients are more likely than migraineurs without vestibular symptoms to experience headaches located in the back of the head, that is, occipital headaches.

Methods: A retrospective cross-sectional study was conducted at the University of Iowa Hospital and Clinics. Chart analysis of 169 patients was performed. The primary outcome was the location of the headache in vestibular migraine patients and migraineurs without vestibular symptoms. The secondary outcomes included the association of vestibular migraine with gender, age at onset of headache, age at onset of vestibular symptoms (such as vertigo, head motion-induced dizziness), aura, motion sickness, other associated symptoms, family history of headaches, and family history of motion sickness.

Results: In vestibular migraine group, 45/103 (44%) had occipital location for their headaches vs 12/66 (18%) in migraine patients without vestibular symptoms, for an odd's ratio of 3.5 (95% CI = 1.7-7.2, P < .001). Additionally, the age at onset of headache was greater in the vestibular migraine group (28 ± 12 vs 18 ± 9 years, P < .001) and motion sickness was more common (41/98 (42%) in the vestibular migraine group, 1/64 (2%) in the migraine without vestibular symptoms group, P < .001).

Conclusions: This study suggests that patients with vestibular migraine are more likely to have occipital headaches than patients with migraine without vestibular symptoms. Our data support the initiation of a prospective study to determine whether a patient presenting with occipital headaches, with late onset of age of headache, and with a history of motion sickness is at an increased risk for the possible development of vestibular migraine.
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http://dx.doi.org/10.1111/head.13898DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7771256PMC
September 2020

Calcitonin gene-related peptide (CGRP): role in migraine pathophysiology and therapeutic targeting.

Expert Opin Ther Targets 2020 02 13;24(2):91-100. Epub 2020 Feb 13.

Department of Physiology and Biophysics, University of Iowa, Iowa City, IA, USA.

: The neuropeptide calcitonin gene-related peptide (CGRP) is recognized as a critical player in migraine pathophysiology. Excitement has grown regarding CGRP because of the development and clinical testing of drugs targeting CGRP or its receptor. While these drugs alleviate migraine symptoms in half of the patients, the remaining unresponsive half of this population creates an impetus to address unanswered questions that exist in this field.: We describe the role of CGRP in migraine pathophysiology and CGRP-targeted therapeutics currently under development and in use. We also discuss how a second CGRP receptor may provide a new therapeutic target.: CGRP-targeting drugs have shown a remarkable safety profile. We speculate that this may reflect the redundancy of peptides within the CGRP family and a second CGRP receptor that may compensate for reduced CGRP activity. Furthermore, we propose that an inherent safety feature of peptide-blocking antibodies is attributed to the fundamental nature of peptide release, which occurs as a large bolus in short bursts of volume transmission. These facts support the development of more refined CGRP therapeutic drugs, as well as drugs that target other neuropeptides. We believe that the future of migraine research is bright with exciting advances on the horizon.
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http://dx.doi.org/10.1080/14728222.2020.1724285DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7050542PMC
February 2020

Peripherally administered calcitonin gene-related peptide induces spontaneous pain in mice: implications for migraine.

Pain 2018 Nov;159(11):2306-2317

Department of Molecular Physiology and Biophysics, University of Iowa Carver College of Medicine, University of Iowa, Iowa City, IA, United States.

Migraine is the third most common disease in the world (behind dental caries and tension-type headache) with an estimated global prevalence of 15%, yet its etiology remains poorly understood. Recent clinical trials have heralded the potential of therapeutic antibodies that block the actions of the neuropeptide calcitonin gene-related peptide (CGRP) or its receptor to prevent migraine. Calcitonin gene-related peptide is believed to contribute to trigeminal nerve hypersensitivity and photosensitivity in migraine, but a direct role in pain associated with migraine has not been established. In this study, we report that peripherally administered CGRP can act in a light-independent manner to produce spontaneous pain in mice that is manifested as a facial grimace. As an objective validation of the orbital tightening action unit of the grimace response, we developed a squint assay using a video-based measurement of the eyelid fissure, which confirmed a significant squint response after CGRP injection, both in complete darkness and very bright light. These indicators of discomfort were completely blocked by preadministration of a monoclonal anti-CGRP-blocking antibody. However, the nonsteroidal anti-inflammatory drug meloxicam failed to block the effect of CGRP. Interestingly, an apparent sex-specific response to treatment was observed with the antimigraine drug sumatriptan partially blocking the CGRP response in male, but not female mice. These results demonstrate that CGRP can induce spontaneous pain, even in the absence of light, and that the squint response provides an objective biomarker for CGRP-induced pain that is translatable to humans.
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http://dx.doi.org/10.1097/j.pain.0000000000001337DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6193822PMC
November 2018

ASIC1A in the bed nucleus of the stria terminalis mediates TMT-evoked freezing.

Front Neurosci 2015 21;9:239. Epub 2015 Jul 21.

Department of Psychiatry, University of Iowa Iowa City, IA, USA ; Department of Veterans Affairs Medical Center Iowa City, IA, USA ; Department of Molecular Physiology and Biophysics, University of Iowa Iowa City, IA, USA.

Mice display an unconditioned freezing response to TMT, a predator odor isolated from fox feces. Here we found that in addition to freezing, TMT caused mice to decrease breathing rate, perhaps because of the aversive smell. Consistent with this possibility, olfactory bulb lesions attenuated this effect of TMT, as well as freezing. Interestingly, butyric acid, another foul odor, also caused mice to reduce breathing rate. However, unlike TMT, butyric acid did not induce freezing. Thus, although these aversive odors may affect breathing, the unpleasant smell and suppression of breathing by themselves are insufficient to cause freezing. Because the acid-sensing ion channel-1A (ASIC1A) has been previously implicated in TMT-evoked freezing, we tested whether Asic1a disruption also altered breathing. We found that TMT reduced breathing rate in both Asic1a(+/+) and Asic1a(-/-) mice, suggesting that ASIC1A is not required for TMT to inhibit breathing and that the absence of TMT-evoked freezing in the Asic1a(-/-) mice is not due to an inability to detect TMT. These observations further indicate that ASIC1A must affect TMT freezing in another way. Because the bed nucleus of the stria terminalis (BNST) has been critically implicated in TMT-evoked freezing and robustly expresses ASIC1A, we tested whether ASIC1A in the BNST plays a role in TMT-evoked freezing. We disrupted ASIC1A in the BNST of Asic1a(loxP/loxP) mice by delivering Cre recombinase to the BNST with an adeno-associated virus (AAV) vector. We found that disrupting ASIC1A in the BNST reduced TMT-evoked freezing relative to control mice in which a virus expressing eGFP was injected. To test whether ASIC1A in the BNST was sufficient to increase TMT-evoked freezing, we used another AAV vector to express ASIC1A in the BNST of Asic1a(-/-) mice. We found region-restricted expression of ASIC1A in the BNST increased TMT-elicited freezing. Together, these data suggest that the BNST is a key site of ASIC1A action in TMT-evoked freezing.
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http://dx.doi.org/10.3389/fnins.2015.00239DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4508508PMC
August 2015

Seizures are regulated by ubiquitin-specific peptidase 9 X-linked (USP9X), a de-ubiquitinase.

PLoS Genet 2015 Mar 12;11(3):e1005022. Epub 2015 Mar 12.

Department of Pediatrics, The University of Iowa, Iowa City, Iowa, United States of America; Interdisciplinary Program in Genetics, The University of Iowa, Iowa City, Iowa, United States of America; Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, Iowa, United States of America; Interdisciplinary Graduate Program in Molecular and Cellular Biology, The University of Iowa, Iowa City, Iowa, United States of America; Interdisciplinary Graduate Program in Neuroscience, The University of Iowa, Iowa City, Iowa, United States of America.

Epilepsy is a common disabling disease with complex, multifactorial genetic and environmental etiology. The small fraction of epilepsies subject to Mendelian inheritance offers key insight into epilepsy disease mechanisms; and pathologies brought on by mutations in a single gene can point the way to generalizable therapeutic strategies. Mutations in the PRICKLE genes can cause seizures in humans, zebrafish, mice, and flies, suggesting the seizure-suppression pathway is evolutionarily conserved. This pathway has never been targeted for novel anti-seizure treatments. Here, the mammalian PRICKLE-interactome was defined, identifying prickle-interacting proteins that localize to synapses and a novel interacting partner, USP9X, a substrate-specific de-ubiquitinase. PRICKLE and USP9X interact through their carboxy-termini; and USP9X de-ubiquitinates PRICKLE, protecting it from proteasomal degradation. In forebrain neurons of mice, USP9X deficiency reduced levels of Prickle2 protein. Genetic analysis suggests the same pathway regulates Prickle-mediated seizures. The seizure phenotype was suppressed in prickle mutant flies by the small-molecule USP9X inhibitor, Degrasyn/WP1130, or by reducing the dose of fat facets a USP9X orthologue. USP9X mutations were identified by resequencing a cohort of patients with epileptic encephalopathy, one patient harbored a de novo missense mutation and another a novel coding mutation. Both USP9X variants were outside the PRICKLE-interacting domain. These findings demonstrate that USP9X inhibition can suppress prickle-mediated seizure activity, and that USP9X variants may predispose to seizures. These studies point to a new target for anti-seizure therapy and illustrate the translational power of studying diseases in species across the evolutionary spectrum.
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http://dx.doi.org/10.1371/journal.pgen.1005022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4357451PMC
March 2015

The bed nucleus of the stria terminalis is critical for anxiety-related behavior evoked by CO2 and acidosis.

J Neurosci 2014 Jul;34(31):10247-55

Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, Iowa 52242, Department of Psychiatry, University of Iowa, Iowa City, Iowa 52242, Medical Scientist Training Program, University of Iowa, Iowa City, Iowa 52242, Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242, Department of Neurosurgery, University of Iowa, Iowa City, Iowa 52242, and Department of Veterans Affairs Medical Center, Iowa City, Iowa 52246

Carbon dioxide (CO2) inhalation lowers brain pH and induces anxiety, fear, and panic responses in humans. In mice, CO2 produces freezing and avoidance behavior that has been suggested to depend on the amygdala. However, a recent study in humans with bilateral amygdala lesions revealed that CO2 can trigger fear and panic even in the absence of amygdalae, suggesting the importance of extra-amygdalar brain structures. Because the bed nucleus of the stria terminalis (BNST) contributes to fear- and anxiety-related behaviors and expresses acid-sensing ion channel-1A (ASIC1A), we hypothesized that the BNST plays an important role in CO2-evoked fear-related behaviors in mice. We found that BNST lesions decreased both CO2-evoked freezing and CO2-conditioned place avoidance. In addition, we found that CO2 inhalation caused BNST acidosis and that acidosis was sufficient to depolarize BNST neurons and induce freezing behavior; both responses depended on ASIC1A. Finally, disrupting Asic1a specifically in the BNST reduced CO2-evoked freezing, whereas virus-vector-mediated expression of ASIC1A in the BNST of Asic1a(-/-) and Asic1a(+/+) mice increased CO2-evoked freezing. Together, these findings identify the BNST as an extra-amygdalar fear circuit structure important in CO2-evoked fear-related behavior.
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http://dx.doi.org/10.1523/JNEUROSCI.1680-14.2014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4115136PMC
July 2014

Acid-sensing ion channels contribute to synaptic transmission and inhibit cocaine-evoked plasticity.

Nat Neurosci 2014 Aug 22;17(8):1083-91. Epub 2014 Jun 22.

1] Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, USA. [2] Department of Psychiatry, University of Iowa, Iowa City, Iowa, USA. [3] Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, Iowa, USA. [4] Department of Neurosurgery, University of Iowa, Iowa City, Iowa, USA. [5] Department of Veterans Affairs Medical Center, Iowa City, Iowa, USA.

Acid-sensing ion channel 1A (ASIC1A) is abundant in the nucleus accumbens (NAc), a region known for its role in addiction. Because ASIC1A has been suggested to promote associative learning, we hypothesized that disrupting ASIC1A in the NAc would reduce drug-associated learning and memory. However, contrary to this hypothesis, we found that disrupting ASIC1A in the mouse NAc increased cocaine-conditioned place preference, suggesting an unexpected role for ASIC1A in addiction-related behavior. Moreover, overexpressing ASIC1A in rat NAc reduced cocaine self-administration. Investigating the underlying mechanisms, we identified a previously unknown postsynaptic current during neurotransmission that was mediated by ASIC1A and ASIC2 and thus well positioned to regulate synapse structure and function. Consistent with this possibility, disrupting ASIC1A altered dendritic spine density and glutamate receptor function, and increased cocaine-evoked plasticity, which resemble changes previously associated with cocaine-induced behavior. Together, these data suggest that ASIC1A inhibits the plasticity underlying addiction-related behavior and raise the possibility of developing therapies for drug addiction by targeting ASIC-dependent neurotransmission.
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http://dx.doi.org/10.1038/nn.3750DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4115047PMC
August 2014

Mechanisms of sudden unexpected death in epilepsy: the pathway to prevention.

Nat Rev Neurol 2014 May 22;10(5):271-82. Epub 2014 Apr 22.

Department of Neurology, University of Iowa, 200 Hawkins Drive, 2 RCP, Iowa City, IA 52242, USA.

Sudden unexpected death in epilepsy (SUDEP) is the leading cause of death in patients with refractory epilepsy, with an estimated 35% lifetime risk in this patient population. There is a surprising lack of awareness among patients and physicians of this increased risk of sudden death: in a recent survey, only 33% of Canadian paediatricians who treated patients with epilepsy knew the term SUDEP. Controversy prevails over whether cardiac arrhythmia or respiratory arrest is more important as the primary cause of death. Effective preventive strategies in high-risk patients will rely on definition of the mechanisms that lead from seizures to death. Here, we summarize evidence for the mechanisms that cause cardiac, respiratory and arousal abnormalities during the ictal and postictal period. We highlight potential cellular mechanisms underlying these abnormalities, such as a defect in the serotonergic system, ictal adenosine release, and changes in autonomic output. We discuss genetic mutations that cause Dravet and long QT syndromes, both of which are linked with increased risk of sudden death. We then highlight possible preventive interventions that are likely to decrease SUDEP incidence, including respiratory monitoring in epilepsy monitoring units and overnight supervision. Finally, we discuss treatments, such as selective serotonin reuptake inhibitors, that might be personalized to a specific genetic or pathological defect.
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http://dx.doi.org/10.1038/nrneurol.2014.64DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4565133PMC
May 2014

Defective motile cilia in Prickle2-deficient mice.

J Neurogenet 2014 Mar-Jun;28(1-2):146-52. Epub 2014 Apr 7.

Department of Neurology, The University of Iowa , Iowa City, Iowa , USA.

Motile cilia play diverse roles across phyla and cell types, and abnormalities in motile cilia lead to numerous disease states, including hydrocephalus. Although motile ciliary abnormalities in Prickle2 mutants have not yet been described, the planar cell polarity genes, including Prickle2, are implicated in the development and function of motile cilia. This report evaluates Prickle2-deficient mice for dysfunction in processes known to depend on functioning motile cilia. Prickle2-deficient mice do not develop hydrocephalus, but do display abnormal morphology and motility in the motile cilia of the ependyma. The morphology of tracheal motile cilia is also abnormal. Taken together, these results demonstrate that Prickle2 is required for normal ependymal motile cilia development and function.
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http://dx.doi.org/10.3109/01677063.2014.885966DOI Listing
January 2015

PRICKLE1 interaction with SYNAPSIN I reveals a role in autism spectrum disorders.

PLoS One 2013 3;8(12):e80737. Epub 2013 Dec 3.

The University of Iowa, Iowa City, Iowa, United States of America ; Department of Pediatrics, The University of Iowa, Iowa City, Iowa, United States of America ; Interdisciplinary Program in Genetics, The University of Iowa, Iowa City, Iowa, United States of America.

The frequent comorbidity of Autism Spectrum Disorders (ASDs) with epilepsy suggests a shared underlying genetic susceptibility; several genes, when mutated, can contribute to both disorders. Recently, PRICKLE1 missense mutations were found to segregate with ASD. However, the mechanism by which mutations in this gene might contribute to ASD is unknown. To elucidate the role of PRICKLE1 in ASDs, we carried out studies in Prickle1(+/-) mice and Drosophila, yeast, and neuronal cell lines. We show that mice with Prickle1 mutations exhibit ASD-like behaviors. To find proteins that interact with PRICKLE1 in the central nervous system, we performed a yeast two-hybrid screen with a human brain cDNA library and isolated a peptide with homology to SYNAPSIN I (SYN1), a protein involved in synaptogenesis, synaptic vesicle formation, and regulation of neurotransmitter release. Endogenous Prickle1 and Syn1 co-localize in neurons and physically interact via the SYN1 region mutated in ASD and epilepsy. Finally, a mutation in PRICKLE1 disrupts its ability to increase the size of dense-core vesicles in PC12 cells. Taken together, these findings suggest PRICKLE1 mutations contribute to ASD by disrupting the interaction with SYN1 and regulation of synaptic vesicles.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0080737PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3849077PMC
August 2014

Sudden unexpected death in epilepsy: fatal post-ictal respiratory and arousal mechanisms.

Respir Physiol Neurobiol 2013 Nov 23;189(2):315-23. Epub 2013 May 23.

Department of Neurology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA 52242, United States; Roy J. and Lucille A. Carver College of Medicine, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA 52242, United States.

Sudden unexplained death in epilepsy (SUDEP) is the cause of premature death of up to 17% of all patients with epilepsy and as many as 50% with chronic refractory epilepsy. However, SUDEP is not widely recognized to exist. The etiology of SUDEP remains unclear, but growing evidence points to peri-ictal respiratory, cardiac, or autonomic nervous system dysfunction. How seizures affect these systems remains uncertain. Here we focus on respiratory mechanisms believed to underlie SUDEP. We highlight clinical evidence that indicates peri-ictal hypoxemia occurs in a large percentage of patients due to central apnea, and identify the proposed anatomical regions of the brain governing these responses. In addition, we discuss animal models used to study peri-ictal respiratory depression. We highlight the role 5-HT neurons play in respiratory control, chemoreception, and arousal. Finally, we discuss the evidence that 5-HT deficits contribute to SUDEP and sudden infant death syndrome and the striking similarities between the two.
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http://dx.doi.org/10.1016/j.resp.2013.05.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4467545PMC
November 2013
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