SCN3A ‐related neurodevelopmental disorder: A spectrum of epilepsy and brain malformation

Zaman, Tariq, Helbig, Katherine L., Clatot, Jérôme, Thompson, Christopher H., Kang, Seok Kyu, Stouffs, Katrien, Jansen, Anna E., Verstraete, Lieve, Jacquinet, Adeline, Parrini, Elena, Guerrini, Renzo, Fujiwara, Yuh, Miyatake, Satoko, Ben-Zeev, Bruria, Bassan, Haim, Reish, Orit, Marom, Daphna, Hauser, Natalie, Vu, Thuy?Anh, Ackermann, Sally, Spencer, Careni E., Lippa, Natalie, Srinivasan, Shraddha, Charzewska, Agnieszka, Hoffman-Zacharska, Dorota, Fitzpatrick, David, Harrison, Victoria, Vasudevan, Pradeep, Joss, Shelagh, Pilz, Daniela T., Fawcett, Katherine A., Helbig, Ingo, Matsumoto, Naomichi, Kearney, Jennifer A., Fry, Andrew E. ORCID: https://orcid.org/0000-0001-9778-6924 and Goldberg, Ethan M. 2020. SCN3A ‐related neurodevelopmental disorder: A spectrum of epilepsy and brain malformation. Annals of Neurology 88 (2) , pp. 348-362. 10.1002/ana.25809

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Abstract

Objective Pathogenic variants in SCN3A , encoding the voltage‐gated sodium channel subunit Nav1.3, cause severe childhood‐onset epilepsy and malformation of cortical development. Here, we define the spectrum of clinical, genetic, and neuroimaging features of SCN3A ‐related neurodevelopmental disorder. Methods Patients were ascertained via an international collaborative network. We compared sodium channels containing wild‐type vs. variant Nav1.3 subunits co‐expressed with β1 and β2 subunits using whole‐cell voltage clamp electrophysiological recordings in a heterologous mammalian system (HEK‐293 T cells). Results Of 22 patients with pathogenic SCN3A variants, most had treatment‐resistant epilepsy beginning in the first year of life (16/21, 76%; median onset, 2 weeks), with severe or profound developmental delay (15/20; 75%). Many, but not all (15/19; 79%), exhibited malformations of cortical development. Pathogenic variants clustered in transmembrane segments 4–6 of domains II‐IV. Most pathogenic missense variants tested (10/11; 91%) displayed gain of channel function, with increased persistent current and/or a leftward shift in the voltage dependence of activation, and all variants associated with malformation of cortical development exhibited gain of channel function. One variant (p.Ile1468Arg) exhibited mixed effects, with gain and partial loss of function. Two variants demonstrated loss of channel function. Interpretation Our study defines SCN3A‐ related neurodevelopmental disorder along a spectrum of severity, but typically including epilepsy and severe or profound developmental delay/intellectual disability. Malformations of cortical development are a characteristic feature of this unusual channelopathy syndrome, present in over 75% of affected individuals. Gain of function at the channel level in developing neurons is likely an important mechanism of disease pathogenesis.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Medicine
Publisher:	Wiley
ISSN:	0364-5134
Date of First Compliant Deposit:	16 June 2020
Date of Acceptance:	25 May 2020
Last Modified:	13 Nov 2023 08:01
URI:	https://orca.cardiff.ac.uk/id/eprint/132507

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