Broadening the scope of multigene panel analysis for adult epilepsy patients.

OBJECTIVE: Epilepsy is a suitable target for gene panel sequencing because a considerable portion of epilepsy is now explained by genetic components, especially in syndromic cases. However, previous gene panel studies on epilepsy have mostly focused on pediatric patients. METHODS: We enrolled adult epilepsy patients meeting any of the following criteria: family history of epilepsy, seizure onset age ≤ 19 years, neuronal migration disorder, and seizure freedom not achieved by dual anti-seizure medications. We sequenced the exonic regions of 211 epilepsy genes in these patients. To confirm the pathogenicity of a novel MTOR truncating variant, we electroporated vectors with different MTOR variants into developing mouse brains. RESULTS: A total of 92 probands and 4 affected relatives were tested, and the proportion of intellectual disability (ID) and/or developmental disability (DD) was 21.7%. As a result, twelve probands (13.0%) had pathogenic or likely pathogenic variants in the following genes or regions: DEPDC5, 15q12-q13 duplication (n = 2), SLC6A1, SYNGAP1, EEF1A2, LGI1, MTOR, KCNQ2, MEF2C, and TSC1 (n = 1). We confirmed the functional impact of a novel truncating mutation in the MTOR gene (c.7570C > T, p.Gln2524Ter) that disrupted neuronal migration in a mouse model. The diagnostic yield was higher in patients with ID/DD or childhood-onset seizures. We also identified additional candidate variants in 20 patients that could be reassessed by further studies. SIGNIFICANCE: Our findings underscore the clinical utility of gene panel sequencing in adult epilepsy patients suspected of having genetic etiology, especially those with ID/DD or early-onset seizures. Gene panel sequencing could not only lead to genetic diagnosis in a substantial portion of adult epilepsy patients but also inform more precise therapeutic decisions based on their genetic background. PLAIN LANGUAGE SUMMARY: This study demonstrated the effectiveness of gene panel sequencing in adults with epilepsy, revealing pathogenic or likely pathogenic variants in 13.0% of patients. Higher diagnostic yields were observed in those with neurodevelopmental disorders or childhood-onset seizures. Additionally, we have shown that expanding genetic studies into adult patients would uncover new types of pathogenic variants for epilepsy, contributing to the advancement of precision medicine for individuals with epilepsy. In conclusion, our results highlight the practical value of employing gene panel sequencing in adult epilepsy patients, particularly when genetic etiology is clinically suspected.

Reversibility and developmental neuropathology of linear nevus sebaceous syndrome caused by dysregulation of the RAS pathway.

Linear nevus sebaceous syndrome (LNSS) is a neurocutaneous disorder caused by somatic gain-of-function mutations in KRAS or HRAS. LNSS brains have neurodevelopmental defects, including cerebral defects and epilepsy; however, its pathological mechanism and potentials for treatment are largely unclear. We show that introduction of KRASG12V in the developing mouse cortex results in subcortical nodular heterotopia and enhanced excitability, recapitulating major pathological manifestations of LNSS. Moreover, we show that decreased firing frequency of inhibitory neurons without KRASG12V expression leads to disrupted excitation and inhibition balance. Transcriptional profiling after destabilization domain-mediated clearance of KRASG12V in human neural progenitors and differentiating neurons identifies reversible functional networks underlying LNSS. Neurons expressing KRASG12V show molecular changes associated with delayed neuronal maturation, most of which are restored by KRASG12V clearance. These findings provide insights into the molecular networks underlying the reversibility of some of the neuropathologies observed in LNSS caused by dysregulation of the RAS pathway.