Abstracts

Rationale: The SCN1A gene encodes the voltage-gated Na+ channel alpha subunit Nav1.1 and is the most clinically relevant epilepsy gene. Variants in SCN1A result in a broad phenotypic spectrum of epilepsy syndromes, from mild genetic epilepsy with febrile seizures plus to severe Dravet syndrome (DS).

Methods: Here, we generated induced pluripotent stem cells (iPSCs) from a normal individual by electroporation of peripheral blood mononuclear cells (PBMCs) and further generated an SCN1A-knockout human iPSC line via CRISPR/Cas9 gene editing. The resulting iPSCs had a normal karyotype, were free of genomically integrated epitomal plasmids, expressed pluripotency markers, and maintained trilineage differentiation potential.

Results: The SCN1A-knockout induced pluripotent stem cell (iPSC) line is useful for modeling refractory epilepsy in vitro, studying the molecular basis of the disease, investigating the in vitro electric properties of the neuronal network for genetic epilepsy and screening novel anti-epilepsy drugs, especially for SCN1A mutation-induced genetic epilepsy.

Conclusions: Most SCN1A mutation patients exhibit subsequent developmental slowing and comorbidities, including autism-like behavior and behavioral difficulties. Approximately 80% of DS patients carry deleterious variants in the SCN1A gene. However, variants in SCN1A are not limited only to DS and have also been identified in patients with other clinical phenotypes, including febrile seizures (simple or complex), intractable childhood epilepsy with generalized tonic-clonic seizures (ICE-GTC), epilepsy of infancy with migrating focal seizures (EIMFS), myoclonic-astatic epilepsy (MAE, Doose syndrome), Lennox-Gastaut syndrome (LGS), infantile spasms (West syndrome) or even hemiplegic migraine.

More than 1910 variants have been identified in the SCN1A gene (Human Gene Variant Database 2019.4). Small DNA variations accounted for 92.8% (1773); missense/nonsense accounted for 60.0% (1283), small deletions and insertions accounted for 23.9% (343 and 114, respectively), small indels accounted for 1.7% (32) and splice site variants accounted for 9.2% (176). Large structural variations accounted for the remaining 7.2% (137) of variants, with 5.9% (111) gross deletions, 0.8% (16) gross duplications and 0.5% (10) complex rearrangements. There were no hot spot variants in the SCN1A gene. Most SCN1A variants are novel and distributed throughout the gene. Genotype‐phenotype correlations were not clear. Moreover, the pathogenicity impact of missense variants on channel function was difficult to predict without functional studies, especially for missense variants.

Funding: Please list any funding that was received in support of this abstract.: This work was supported by the China Postdoctoral Science Foundation (No. 2019M660719) and Beijing Postdoctoral Research Foundation (ZZ 2019-09).