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Abstract
Neurologic disease in horses can be particularly challenging to diagnose and treat. These diseases can result in economic losses, emotional distress to owners, and injury to the horse or handlers. To date, there are 5 neurologic diseases caused by known genetic mutations and several more are suspected to be heritable: lethal white foal syndrome, lavender foal syndrome, cerebellar abiotrophy, occipitoatlantoaxial malformation, and Friesian hydrocephalus. Genetic testing allows owners, breeders, and veterinarians to make informed decisions when selecting dams and sires for breeding or deciding the treatment or prognosis of a neurologic animal.
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Affiliation(s)
- Lisa Edwards
- Department of Veterinary Population Health and Reproduction, School of Veterinary Medicine, University of California Davis, Room 4206 Vet Med 3A One Shields Avenue, Davis, CA 95616, USA
| | - Carrie J Finno
- Department of Veterinary Population Health and Reproduction, School of Veterinary Medicine, University of California Davis, Room 4206 Vet Med 3A One Shields Avenue, Davis, CA 95616, USA.
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Ekenstedt KJ, Oberbauer AM. Inherited epilepsy in dogs. Top Companion Anim Med 2014; 28:51-8. [PMID: 24070682 DOI: 10.1053/j.tcam.2013.07.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Accepted: 07/01/2013] [Indexed: 12/15/2022]
Abstract
Epilepsy is the most common neurologic disease in dogs and many forms are considered to have a genetic basis. In contrast, some seizure disorders are also heritable, but are not technically defined as epilepsy. Investigation of true canine epilepsies has uncovered genetic associations in some cases, however, many remain unexplained. Gene mutations have been described for 2 forms of canine epilepsy: primary epilepsy (PE) and progressive myoclonic epilepsies. To date, 9 genes have been described to underlie progressive myoclonic epilepsies in several dog breeds. Investigations into genetic PE have been less successful, with only 1 causative gene described. Genetic testing as an aid to diagnosis, prognosis, and breeding decisions is available for these 10 forms. Additional studies utilizing genome-wide tools have identified PE loci of interest; however, specific genetic tests are not yet developed. Many studies of dog breeds with PE have failed to identify genes or loci of interest, suggesting that, similar to what is seen in many human genetic epilepsies, inheritance is likely complex, involving several or many genes, and reflective of environmental interactions. An individual dog's response to therapeutic intervention for epilepsy may also be genetically complex. Although the field of inherited epilepsy has faced challenges, particularly with PE, newer technologies contribute to further advances.
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Affiliation(s)
- Kari J Ekenstedt
- Department of Animal and Food Science, College of Agriculture, Food, and Environmental Sciences, University of Wisconsin - River Falls, River Falls, WI, USA.
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Jefferys JGR. Are Changes in Synaptic Function That Underlie Hyperexcitability Responsible for Seizure Activity? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 813:185-94. [DOI: 10.1007/978-94-017-8914-1_15] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Hitomi Y, Heinzen EL, Donatello S, Dahl HH, Damiano JA, McMahon JM, Berkovic SF, Scheffer IE, Legros B, Rai M, Weckhuysen S, Suls A, De Jonghe P, Pandolfo M, Goldstein DB, Van Bogaert P, Depondt C. Mutations in TNK2 in severe autosomal recessive infantile onset epilepsy. Ann Neurol 2013; 74:496-501. [PMID: 23686771 DOI: 10.1002/ana.23934] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 04/30/2013] [Accepted: 05/01/2013] [Indexed: 01/27/2023]
Abstract
We identified a small family with autosomal recessive, infantile onset epilepsy and intellectual disability. Exome sequencing identified a homozygous missense variant in the gene TNK2, encoding a brain-expressed tyrosine kinase. Sequencing of the coding region of TNK2 in 110 patients with a similar phenotype failed to detect further homozygote or compound heterozygote mutations. Pathogenicity of the variant is supported by the results of our functional studies, which demonstrated that the variant abolishes NEDD4 binding to TNK2, preventing its degradation after epidermal growth factor stimulation. Definitive proof of pathogenicity will require confirmation in unrelated patients.
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Affiliation(s)
- Yuki Hitomi
- Duke Center for Human Genome Variation, Duke University School of Medicine, Durham, NC
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High incidence of pediatric idiopathic epilepsy is associated with familial and autosomal dominant disease in Eastern Newfoundland. Epilepsy Res 2011; 98:140-7. [PMID: 21959335 DOI: 10.1016/j.eplepsyres.2011.09.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Revised: 07/29/2011] [Accepted: 09/03/2011] [Indexed: 11/20/2022]
Abstract
PURPOSE To describe the incidence and epidemiology of pediatric idiopathic epilepsy (IE) in Newfoundland and Labrador. METHODS All children in Newfoundland and Labrador aged 0-15 years with IE were ascertained through the provincial neurology clinic at the Janeway Child Health Centre. Family history, medical history and blood samples were obtained from probands and relatives. Two genes, SCN1A and KCNQ2, were screened for mutations by direct sequencing. RESULTS The mean annual incidence of IE for the population of children living in the Avalon region of Newfoundland from 2000 to 2004 was 107 per 100,000. This rate is approximately three-fold greater than rates reported in other developed countries. Of 117 families with IE eligible for study, 86 (74%) provided detailed pedigree data. Multiple different epilepsy phenotypes were identified. Fifty-five families (64%) had a positive family history. Eight of these had family histories compatible with autosomal dominant (AD) inheritance and these families lived in five different geographic isolates. DNA was obtained from 21 families (79 individuals). The two previously identified mutations in Newfoundland families with epilepsy were sequenced and excluded as pathogenic sites in all but one family which had a mutation in SCN1A. CONCLUSION The incidence of IE is high in the Avalon Peninsula of Newfoundland and the rate of familial disease is high throughout the province of Newfoundland and Labrador. The distribution of familial and AD IE in different geographic isolates, together with the clinical heterogeneity of disease suggests substantial genetic heterogeneity. It is likely that other novel mutations will be identified in this population.
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Ohno Y, Ishihara S, Mashimo T, Sofue N, Shimizu S, Imaoku T, Tsurumi T, Sasa M, Serikawa T. Scn1a missense mutation causes limbic hyperexcitability and vulnerability to experimental febrile seizures. Neurobiol Dis 2010; 41:261-9. [PMID: 20875856 DOI: 10.1016/j.nbd.2010.09.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Revised: 08/15/2010] [Accepted: 09/19/2010] [Indexed: 11/29/2022] Open
Abstract
Mutations of the voltage-gated sodium (Na(v)) channel subunit SCN1A have been implicated in the pathogenesis of human febrile seizures including generalized epilepsy with febrile seizures plus (GEFS+) and severe myoclonic epilepsy in infancy (SMEI). Hyperthermia-induced seizure-susceptible (Hiss) rats are the novel rat model carrying a missense mutation (N1417H) of Scn1a, which is located in the third pore-forming region of the Na(v)1.1 channel. Here, we conducted behavioral and neurochemical studies to clarify the functional relevance of the Scn1a mutation in vivo and the mechanism underlying the vulnerability to hyperthermic seizures. Hiss rats showed markedly high susceptibility to hyperthermic seizures (mainly generalized clonic seizures) which were synchronously associated with paroxysmal epileptiform discharges. Immunohistochemical analysis of brain Fos expression revealed that hyperthermic seizures induced a widespread elevation of Fos-immunoreactivity in the cerebral cortices including the motor area, piriform, and insular cortex. In the subcortical regions, hyperthermic seizures enhanced Fos expression region--specifically in the limbic and paralimbic regions (e.g., hippocampus, amygdala, and perirhinal-entorhinal cortex) without affecting other brain regions (e.g., basal ganglia, diencephalon, and lower brainstem), suggesting a primary involvement of limbic system in the induction of hyperthermic seizures. In addition, Hiss rats showed a significantly lower threshold than the control animals in inducing epileptiform discharges in response to local stimulation of the hippocampus (hippocampal afterdischarges). Furthermore, hyperthermic seizures in Hiss rats were significantly alleviated by the antiepileptic drugs, diazepam and sodium valproate, while phenytoin or ethosuximide were ineffective. The present findings support the notion that Hiss rats are useful as a novel rat model of febrile seizures and suggest that hyperexcitability of limbic neurons associated with Scn1a missense mutation plays a crucial role in the pathogenesis of febrile seizures.
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Affiliation(s)
- Yukihiro Ohno
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka 569-1094, Japan.
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Chabrol E, Navarro V, Provenzano G, Cohen I, Dinocourt C, Rivaud-Péchoux S, Fricker D, Baulac M, Miles R, Leguern E, Baulac S. Electroclinical characterization of epileptic seizures in leucine-rich, glioma-inactivated 1-deficient mice. ACTA ACUST UNITED AC 2010; 133:2749-62. [PMID: 20659958 PMCID: PMC2929330 DOI: 10.1093/brain/awq171] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mutations of the LGI1 (leucine-rich, glioma-inactivated 1) gene underlie autosomal dominant lateral temporal lobe epilepsy, a focal idiopathic inherited epilepsy syndrome. The LGI1 gene encodes a protein secreted by neurons, one of the only non-ion channel genes implicated in idiopathic familial epilepsy. While mutations probably result in a loss of function, the role of LGI1 in the pathophysiology of epilepsy remains unclear. Here we generated a germline knockout mouse for LGI1 and examined spontaneous seizure characteristics, changes in threshold for induced seizures and hippocampal pathology. Frequent spontaneous seizures emerged in homozygous LGI1−/− mice during the second postnatal week. Properties of these spontaneous events were examined in a simultaneous video and intracranial electroencephalographic recording. Their mean duration was 120 ± 12 s, and behavioural correlates consisted of an initial immobility, automatisms, sometimes followed by wild running and tonic and/or clonic movements. Electroencephalographic monitoring indicated that seizures originated earlier in the hippocampus than in the cortex. LGI1−/− mice did not survive beyond postnatal day 20, probably due to seizures and failure to feed. While no major developmental abnormalities were observed, after recurrent seizures we detected neuronal loss, mossy fibre sprouting, astrocyte reactivity and granule cell dispersion in the hippocampus of LGI1−/− mice. In contrast, heterozygous LGI1+/− littermates displayed no spontaneous behavioural epileptic seizures, but auditory stimuli induced seizures at a lower threshold, reflecting the human pathology of sound-triggered seizures in some patients. We conclude that LGI1+/− and LGI1−/− mice may provide useful models for lateral temporal lobe epilepsy, and more generally idiopathic focal epilepsy.
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Affiliation(s)
- Elodie Chabrol
- CRICM UMR_S975, Hôpital de la Pitié-Salpêtrière, Bâtiment Pharmacie, 47 Boulevard de l'hôpital, Paris, France
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Mashimo T, Ohmori I, Ouchida M, Ohno Y, Tsurumi T, Miki T, Wakamori M, Ishihara S, Yoshida T, Takizawa A, Kato M, Hirabayashi M, Sasa M, Mori Y, Serikawa T. A missense mutation of the gene encoding voltage-dependent sodium channel (Nav1.1) confers susceptibility to febrile seizures in rats. J Neurosci 2010; 30:5744-53. [PMID: 20410126 PMCID: PMC6632336 DOI: 10.1523/jneurosci.3360-09.2010] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Revised: 03/02/2010] [Accepted: 03/10/2010] [Indexed: 11/21/2022] Open
Abstract
Although febrile seizures (FSs) are the most common convulsive syndrome in infants and childhood, the etiology of FSs has remained unclarified. Several missense mutations of the Na(v)1.1 channel (SCN1A), which alter channel properties, have been reported in a familial syndrome of GEFS+ (generalized epilepsy with febrile seizures plus). Here, we generated Scn1a-targeted rats carrying a missense mutation (N1417H) in the third pore region of the sodium channel by gene-driven ENU (N-ethyl-N-nitrosourea) mutagenesis. Despite their normal appearance under ordinary circumstances, Scn1a mutant rats exhibited remarkably high susceptibility to hyperthermia-induced seizures, which involve generalized clonic and/or tonic-clonic convulsions with paroxysmal epileptiform discharges. Whole-cell patch-clamp recordings from HEK cells expressing N1417H mutant channels and from hippocampal GABAergic interneurons of N1417H mutant rats revealed a significant shift of the inactivation curve in the hyperpolarizing direction. In addition, clamp recordings clearly showed the reduction in action potential amplitude in the hippocampal interneurons of these rats. These findings suggest that a missense mutation (N1417H) of the Na(v)1.1 channel confers susceptibility to FS and the impaired biophysical properties of inhibitory GABAergic neurons underlie one of the mechanisms of FS.
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Affiliation(s)
- Tomoji Mashimo
- Institute of Laboratory Animals, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.
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