Low penetrance of autosomal dominant lateral temporal epilepsy in Italian families without LGI1 mutations.

PURPOSE: In relatively small series, autosomal dominant lateral temporal epilepsy (ADLTE) has been associated with leucine-rich, glioma-inactivated 1 (LGI1) mutations in about 50% of the families, this genetic heterogeneity being probably caused by differences in the clinical characteristics of the families. In this article we report the overall clinical and genetic spectrum of ADLTE in Italy with the aim to provide new insight into its nosology and genetic basis. METHODS: In a collaborative study of the Commission of Genetics of the Italian League Against Epilepsy (LICE) encompassing a 10-year period (2000-2010), we collected 33 ADLTE families, selected on the basis of the following criteria: presence of at least two members concordant for unprovoked partial seizures with prominent auditory and or aphasic symptoms, absence of any known structural brain pathology or etiology, and normal neurologic examination. The clinical, neurophysiologic, and neuroradiologic findings of all patients were analyzed and a genealogic tree was built for each pedigree. The probands' DNA was tested for LGI1 mutations by direct sequencing and, if negative, were genotyped with single-nucleotide polymorphism (SNP) array to search for disease-linked copy-number variation CNV. The disease penetrance in mutated and nonmutated families was assessed as a proportion of obligate carriers who were affected. KEY FINDINGS: The 33 families included a total of 127 affected individuals (61 male, 66 female, 22 deceased). The age at onset ranged between 2 and 60 years (mean 18.7 years). Ninety-one patients (72%) had clear-cut focal (elementary, complex, or secondarily generalized) seizures, characterized by prominent auditory auras in 68% of the cases. Other symptoms included complex visual hallucinations, vertigo, and déjà vu. Aphasic seizures, associated or not with auditory features, were observed in 20% of the cases, whereas tonic-clonic seizures occurred in 86% of the overall series. Sudden noises could precipitate the seizures in about 20% of cases. Seizures, which usually occurred at a low frequency, were promptly controlled or markedly improved by antiepileptic treatment in the majority of patients. The interictal electroencephalography (EEG) studies showed the epileptiform temporal abnormalities in 62% of cases, with a slight predominance over the left region. Magnetic resonance imaging (MRI) or computerized tomography (CT) scans were negative. LGI1 mutations (missense in nine and a microdeletion in one) were found in only 10 families (30%). The patients belonging to the mutated and not mutated groups did not differ except for penetrance estimate, which was 61.3% and 35% in the two groups, respectively (chi-square, p = 0.017). In addition, the disease risk of members of families with mutations in LGI1 was three times higher than that of members of LGI1-negative families (odds ratio [OR] 2.94, confidence interval [CI] 1.2-7.21). SIGNIFICANCE: A large number of ADLTE families has been collected over a 10-year period in Italy, showing a typical and homogeneous phenotype. LGI1 mutations have been found in only one third of families, clinically indistinguishable from nonmutated pedigrees. The estimate of penetrance and OR, however, demonstrates a significantly lower penetrance rate and relative disease risk in non-LGI1-mutated families compared with LGI1-mutated pedigrees, suggesting that a complex inheritance pattern may underlie a proportion of these families.

MICAL1 Monooxygenase in Autosomal Dominant Lateral Temporal Epilepsy: Role in Cytoskeletal Regulation and Relation to Cancer.

Autosomal dominant lateral temporal epilepsy (ADLTE) is a genetic focal epilepsy associated with mutations in the LGI1, RELN, and MICAL1 genes. A previous study linking ADLTE with two MICAL1 mutations that resulted in the substitution of a highly conserved glycine residue for serine (G150S) or a frameshift mutation that swapped the last three C-terminal amino acids for 59 extra residues (A1065fs) concluded that the mutations increased enzymatic activity and promoted cell contraction. The roles of the Molecule Interacting with CasL 1 (MICAL1) protein in tightly regulated semaphorin signaling pathways suggest that activating MICAL1 mutations could result in defects in axonal guidance during neuronal development. Further studies would help to illuminate the causal relationships of these point mutations with ADLTE. In this review, we discuss the proposed pathogenesis caused by mutations in these three genes, with a particular emphasis on the G150S point mutation discovered in MICAL1. We also consider whether these types of activating MICAL1 mutations could be linked to cancer.

Autosomal dominant temporal lobe epilepsy associated with heterozygous reelin mutation: 3 T brain MRI study with advanced neuroimaging methods.

PURPOSE: Autosomal dominant lateral temporal epilepsy (ADLTE) is a genetic focal epilepsy syndrome characterized by focal seizures with dominant auditory symptomatology. We present a case report of an 18-year-old patient with acute onset of seizures associated with epilepsy. Based on the clinical course of the disease and the results of the investigation, the diagnosis of ADLTE with a proven mutation in the RELN gene, which is considered causative, was subsequently confirmed. The aim of this study was to use 3 Tesla (3 T) magnetic resonance imaging (MRI) and advanced neuroimaging methods in a patient with a confirmed diagnosis of ADTLE. METHODS: 3 T MRI brain scan and advanced neuroimaging methods were used in the standard protocols to analyzse voxel-based MRI, cortical thickness, and functional connectivity. RESULTS: Morphometric MRI analysis (blurred grey-white matter junctions, voxel-based morphometry, and cortical thickness analysis) did not provide any informative results. The functional connectivity analysis revealed higher local synchrony in the patient in the left temporal (middle temporal gyrus), left frontal (supplementary motor area, superior frontal gyrus), and left parietal (gyrus angularis, gyrus supramarginalis) regions and the cingulate (middle cingulate gyrus) as compared to healthy controls. CONCLUSIONS: Evidence of multiple areas of functional connectivity supports the theory of epileptogenic networks in ADTLE. Further studies are needed to elucidate this theory.

Screening LGI1 in a cohort of 26 lateral temporal lobe epilepsy patients with auditory aura from Turkey detects a novel de novo mutation.

Autosomal dominant lateral temporal lobe epilepsy (ADLTE) is an autosomal dominant epileptic syndrome characterized by focal seizures with auditory or aphasic symptoms. The same phenotype is also observed in a sporadic form of lateral temporal lobe epilepsy (LTLE), namely idiopathic partial epilepsy with auditory features (IPEAF). Heterozygous mutations in LGI1 account for up to 50% of ADLTE families and only rarely observed in IPEAF cases. In this study, we analysed a cohort of 26 individuals with LTLE diagnosed according to the following criteria: focal epilepsy with auditory aura and absence of cerebral lesions on brain MRI. All patients underwent clinical, neuroradiological and electroencephalography examinations and afterwards they were screened for mutations in LGI1 gene. The single LGI1 mutation identified in this study is a novel missense variant (NM_005097.2: c.1013T>C; p.Phe338Ser) observed de novo in a sporadic patient. This is the first study involving clinical analysis of a LTLE cohort from Turkey and genetic contribution of LGI1 to ADLTE phenotype. Identification of rare LGI1 gene mutations in sporadic cases supports diagnosis as ADTLE and draws attention to potential familial clustering of ADTLE in suggestive generations, which is especially important for genetic counselling.

Autosomal dominant lateral temporal epilepsy (ADLTE): absence of chromosomal rearrangements in LGI1 gene.

Mutations of leucine-rich, glioma inactivated 1 (LGI1) gene are found in about half of the families with autosomal dominant lateral temporal epilepsy (ADLTE). More recently a LGI1 heterozygous microdeletion was found in a single ADLTE family, suggesting that submicroscopic chromosomal abnormalities should be investigated in cases negative for LGI1 mutations. This study examines whether microdeletions and duplications of the LG1 gene occurred in eight ADLTE families and 20 sporadic patients that were negative for LGI1 mutations. Multiplex ligation-dependent probe amplification (MLPA) was applied to detect potential deletions and duplications of LGI1 gene. In all patients, MLPA analysis did not reveal any pathogenic changes in the LGI1 gene. Chromosomal rearrangements involving the LGI1 gene were not identified in our series of familial or sporadic LTE. These results further illustrate the considerable genetic heterogeneity for ADLTE, despite the relatively homogeneous clinical picture. There are as yet undiscovered mechanisms underlying ADLTE.