SCN1A-deficient hiPSC-derived excitatory neuronal networks display mutation-specific phenotypes
Authors: van Hugte Eline J.H. , Lewerissa Elly I. , Wu Ka Man , Parodi Giulia , van Voorst Torben , Kogo Naoki , Keller Jason M. , Schubert Dirk , Schelhaas Helenius J. , Verhoeven Judith , Majoie Marian , van Bokhoven Hans , Nadif Kasri Nael 
Published: January 2023

Dravet syndrome is a severe epileptic encephalopathy, characterized by (febrile) seizures, behavioral problems and developmental delay. 80% of Dravet syndrome patients have a mutation inSCN1A, encoding NaV1.1. Milder clinical phenotypes, such as GEFS+(generalized epilepsy with febrile seizures plus), can also arise fromSCN1Amutations. Predicting the clinical phenotypic outcome based on the type of mutation remains challenging, even when the same mutation is inherited within one family. Both this clinical and genetic heterogeneity add to the difficulties of predicting disease progression and tailored prescription of anti-seizure medication. A better understanding of the neuropathology of differentSCN1Amutations, might give insight in differentiating the expected clinical phenotype and best fit treatment choice. Initially it was recognized that loss of Na+-current in inhibitory neurons specifically resulted in disinhibition and consequently seizure generation. However, the extent to which excitatory neurons contribute to the pathophysiology is currently debated, and might depend on the patient clinical phenotype or the specific mutation inSCN1A.

To examine the genotype-phenotype correlations ofSCN1Amutations in relation to excitatory neurons, we investigated a panel of patient-derived excitatory neuronal networks differentiated on multi-electrode arrays. We included patients with different clinical phenotypes, harboring different mutations inSCN1A, plus a family where the same mutation leads to both GEFS+ and Dravet syndrome.

We hitherto describe a previously unidentified functional excitatory neuronal network phenotype in the context of epilepsy, which corresponded to seizurogenic network prediction patterns elicited by proconvulsive compounds. We find that excitatory neuronal networks were differently affected, dependent on the type of SCN1Amutation, but not on clinical severity. Specifically, pore domain mutations could be distinguished from voltage sensing domain mutations. Furthermore, all patients showed aggravated neuronal network responses upon febrile temperatures. While the basal neuronal network phenotypes could not be distinguished based on patient clinical severity, retrospective drug screening revealed that anti-seizure medication only affected GEFS+ patient-, but not Dravet patient-derived neuronal networks in a patient specific and clinically relevant manner. In conclusion, our results indicate a mutation-specific excitatory neuronal network phenotype, which recapitulates the foremost clinically relevant features, providing future opportunities for precision therapies.

Highlights

Human stem cell derived excitatory neurons are affected by mutations inSCN1Aand display mutation-specific, but not clinical phenotype specific, neuronal network phenotypes

The neuronal network phenotype we describe corresponds to seizurogenic network prediction patterns in vitro

Excitatory neuronal networks respond to Dravet syndrome clinically relevant triggers, like febrile temperatures and Dravet-contraindicated ASM Carbamazepine

Retrospective drug screening revealed that GEFS+ neuronal networks, but not Dravet neuronal networks respond to ASM in a patient-specific and clinical relevant manner