Glutamatergic neuron-targeted loss of LGI1 epilepsy gene results in seizures

Boillot, Morgane; Huneau, Clément; Marsan, Elise; Lehongre, Katia; Navarro, Vincent; Ishida, Saeko; Dufresnois, Béatrice; Ozkaynak, Ekim; Garrigue, Jean-Luc; Miles, Richard; Martin, Benoı̂t; LeGuern, Eric; Anderson, Matthew P.; Baulac, Stéphanie

doi:10.1093/brain/awu259

Cited by 47 publications

(57 citation statements)

References 53 publications

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“…Furthermore LGI1 binding to ADAM11 has been reported (28), which suggests that LGI1 may influence synaptic inhibition. However, selective deletion of LGI1 in parvalbumin-positive interneurons did not generate an epileptic phenotype, whereas knock out in glutamatergic neurons resulted in seizures (8), suggesting that loss of LGI1 in excitatory neurons is the predominant factor. Do our present findings have implications for LE with LGI1 autoimmunity?…”

Section: Discussionmentioning

confidence: 97%

“…However, inhibitory synaptic transmission is not affected in LGI1 mutant mice (7,13) and conditional LGI1 knock out in inhibitory parvalbumin interneurons does not confer an epileptic phenotype (8).…”

Section: Discussionmentioning

confidence: 99%

“…Most ADEAF mutations impair secretion of the protein (3,4). Animal models of LGI1 depletion, including Lgi1 −/− mice (5)(6)(7)(8), mutant rats (9), and knockdown in zebrafish (10), all display spontaneous seizures. However, the mechanisms by which LGI1 deficiency leads to epilepsy are unknown.…”

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confidence: 99%

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LGI1 tunes intrinsic excitability by regulating the density of axonal Kv1 channels

Seagar

Russier

Caillard

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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105

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Autosomal dominant epilepsy with auditory features results from mutations in leucine-rich glioma-inactivated 1 (LGI1), a soluble glycoprotein secreted by neurons. Animal models of LGI1 depletion display spontaneous seizures, however, the function of LGI1 and the mechanisms by which deficiency leads to epilepsy are unknown. We investigated the effects of pure recombinant LGI1 and genetic depletion on intrinsic excitability, in the absence of synaptic input, in hippocampal CA3 neurons, a classical focus for epileptogenesis. Our data indicate that LGI1 is expressed at the axonal initial segment and regulates action potential firing by setting the density of the axonal Kv1.1 channels that underlie dendrotoxin-sensitive D-type potassium current.LGI1 deficiency incurs a >50% down-regulation of the expression of Kv1.1 and Kv1.2 via a posttranscriptional mechanism, resulting in a reduction in the capacity of axonal D-type current to limit glutamate release, thus contributing to epileptogenesis.LGI1 | Kv1 channels | D-type current | intrinsic excitability | epilepsy

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

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LGI1 tunes intrinsic excitability by regulating the density of axonal Kv1 channels

Seagar

Russier

Caillard

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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105

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“…They are early-onset and rapidly lethal with clinical and EEG evidence for a hippocampal origin (Chabrol et al, 2010) or myoclonic seizures suggestive of TDS (Fukata et al, 2010;Yu et al, 2010). Selective late postnatal inactivation of the LGI1 gene in glutamatergic pyramidal neurons showed a less severe phenotype (Boillot et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

Motor cortex and hippocampus are the two main cortical targets in LGI1-antibody encephalitis

Navarro¹,

Kas²,

Apartis³

et al. 2016

Brain

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Ã These authors contributed equally to this work. Encephalitis associated with antibodies against leucine-rich glioma-inactivated 1 (LGI1) protein is increasingly recognized as an auto-immune disorder associated with characteristic tonic-dystonic seizures. The cortical or subcortical origin of these motor events is not clear. Some patients also present with different epileptic seizures and with cognitive impairment. The frequency of these features and their timing during the natural history of this encephalitis have not been fully described. We therefore reviewed data from 34 patients harbouring antibodies against LGI1 protein (21-81 years, median age 64) referred to the French Reference Centre for Neurological Paraneoplastic Syndrome. Three types of evidence suggested tonic-dystonic seizures were of cortical origin: (i) a slow, unilateral, frontal electroencephalographic wave, of duration $580 ms and amplitude $71 mV, preceded the contralateral tonic-dystonic seizures in simultaneous electroencephalographic and myographic records from seven of seven patients tested; (ii) 18-Fluorodeoxyglucose imaging revealed a strong hypermetabolism in primary motor cortex, controlateral to the affected limb, during encephalitis for five patients tested, as compared with data from the same patients after remission or from 16 control subjects; and (iii) features of polymyographic records of tonic-dystonic seizure events pointed to a cortical origin. Myoclonic patterns with brief, rhythmic bursts were present in three of five patients tested and a premyoclonic potential was identified in the cortex of one patient. Initially during encephalitis, 11 of 34 patients exhibited tonic-dystonic seizures (32%). Distinct epileptic syndromes were evident in 13 patients (38%). They were typically simple, focal seizures from the temporal lobe, consisting of vegetative symptoms or fear. At later stages, 22 of 32 patients displayed tonic-dystonic seizures (68%) and 29 patients presented frequent seizures (91%) including status epilepticus. Cognitive impairment, either anterograde amnesia or confusion was evident in 30 of 34 patients (88%). Brain imaging was normal in patients with isolated tonic-dystonic seizures; in patients with limbic symptoms it revealed initially a hippocampal hyperintensity in 8 of 19 patients (42%) and 17 of 24 patients (70%) at later stages. Our data suggest that the major signs of LGI1-antibody encephalitis can be linked to involvement of motor cortex and hippocampus. They occur in parallel with striatum involvement. One of these cortical targets is involved, often unilaterally at disease onset. As the encephalitis progresses, in the absence of immunomodulatory treatment, the second cortical target is affected and effects become bilateral. Progression to the second cortical target occurs with a variable delay of days to several months.

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“…Recent work on conditional knockout mice suggests that LGI1, like Reelin, could serve different functions during brain development and adulthood. 50 Given that Reelin and LGI1 co-localize to distinct neurons in both the immature and mature rat brain, it is conceivable that a functional interplay between the two proteins is necessary for proper regulation of various neuronal processes during development and in adult life. Future work will hopefully elucidate the type of interaction between Reelin and LGI1 and how their mutations lead to ADLTE.…”

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confidence: 99%

Heterozygous Reelin Mutations Cause Autosomal-Dominant Lateral Temporal Epilepsy

Dazzo

Fanciulli²,

Serioli

et al. 2015

The American Journal of Human Genetics

106

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Autosomal-dominant lateral temporal epilepsy (ADLTE) is a genetic epilepsy syndrome clinically characterized by focal seizures with prominent auditory symptoms. ADLTE is genetically heterogeneous, and mutations in LGI1 account for fewer than 50% of affected families. Here, we report the identification of causal mutations in reelin (RELN) in seven ADLTE-affected families without LGI1 mutations. We initially investigated 13 ADLTE-affected families by performing SNP-array linkage analysis and whole-exome sequencing and identified three heterozygous missense mutations co-segregating with the syndrome. Subsequent analysis of 15 small ADLTE-affected families revealed four additional missense mutations. 3D modeling predicted that all mutations have structural effects on protein-domain folding. Overall, RELN mutations occurred in 7/40 (17.5%) ADLTE-affected families. RELN encodes a secreted protein, Reelin, which has important functions in both the developing and adult brain and is also found in the blood serum. We show that ADLTE-related mutations significantly decrease serum levels of Reelin, suggesting an inhibitory effect of mutations on protein secretion. We also show that Reelin and LGI1 co-localize in a subset of rat brain neurons, supporting an involvement of both proteins in a common molecular pathway underlying ADLTE. Homozygous RELN mutations are known to cause lissencephaly with cerebellar hypoplasia. Our findings extend the spectrum of neurological disorders associated with RELN mutations and establish a link between RELN and LGI1, which play key regulatory roles in both the developing and adult brain.Temporal-lobe epilepsy is the most common type of focal epilepsy. It is sometimes associated with structural brain lesions, but genetic forms have also been described. Familial temporal-lobe epilepsy comprises two genetically distinct syndromes: familial mesial temporal-lobe epilepsy (FMTLE [MIM: 611630]) 1 and autosomal-dominant lateral temporal epilepsy (ADLTE [MIM: 600512]), also named autosomal-dominant partial epilepsy with auditory features (ADPEAF). 2 ADLTE is a well-defined epileptic syndrome clinically characterized by focal seizures with prominent auditory and/or aphasic symptoms, normal brain MRI, and relatively benign evolution. 2,3 Its inheritance pattern is autosomal dominant with reduced penetrance (around 70%). Mutations associated with ADLTE are found in leucine-rich, glioma inactivated 1 (LGI1 [MIM: 604619]) 4-6 in 30%-50% of ADLTE-affected families. 3,7,8 Other genes harboring ADLTE-causing mutations are unknown.LGI1 is expressed mainly in neurons, particularly in the neocortex and limbic regions, 4,9 and its protein product, LGI1, is secreted. 9 LGI1 has been implicated in the transmission of K þ and AMPA synaptic currents 10,11 and in the regulation of post-natal maturation of cortical excitatory synapses and dendrite pruning. 12 However, it is not known which of these functions underlies ADLTE. Identification of additional genes whose mutations cause ADLTE will help to clarify the pathoge...

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Glutamatergic neuron-targeted loss of LGI1 epilepsy gene results in seizures

Cited by 47 publications

References 53 publications

LGI1 tunes intrinsic excitability by regulating the density of axonal Kv1 channels

LGI1 tunes intrinsic excitability by regulating the density of axonal Kv1 channels

Motor cortex and hippocampus are the two main cortical targets in LGI1-antibody encephalitis

Heterozygous Reelin Mutations Cause Autosomal-Dominant Lateral Temporal Epilepsy

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