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Epilepsia Open December 1, 2020; 5 (4): 562-573.
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Familial neonatal seizures caused by the Kv7.3 selectivity filter mutation T313I.

Maghera J , Li J , Lamothe SM , Braun M , Appendino JP , Au PYB , Kurata HT .

OBJECTIVE: A spectrum of seizure disorders is linked to mutations in Kv7.2 and Kv7.3 channels. Linking functional effects of identified mutations to their clinical presentation requires ongoing characterization of newly identified variants. In this study, we identified and functionally characterized a previously unreported mutation in the selectivity filter of Kv7.3. METHODS: Next-generation sequencing was used to identify the Kv7.3[T313I] mutation in a family affected by neonatal seizures. Electrophysiological approaches were used to characterize the functional effects of this mutation on ion channels expressed in Xenopus laevis oocytes. RESULTS: Substitution of residue 313 from threonine to isoleucine (Kv7.3[T313I]) likely disrupts a critical intersubunit hydrogen bond. Characterization of the mutation in homomeric Kv7.3 channels demonstrated a total loss of channel function. Assembly in heteromeric channels (with Kv7.2) leads to modest suppression of total current when expressed in Xenopus laevis oocytes. Using a Kv7 activator with distinct effects on homomeric Kv7.2 vs heteromeric Kv7.2/Kv7.3 channels, we demonstrated that assembly of Kv7.2 and Kv7.3[T313I] generates functional channels. SIGNIFICANCE: Biophysical and clinical effects of the T313I mutation are consistent with Kv7.3 mutations previously identified in cases of pharmacoresponsive self-limiting neonatal epilepsy. These findings expand our description of functionally characterized Kv7 channel variants and report new methods to distinguish molecular mechanisms of channel mutations.

PubMed ID: 33336127
Article link: Epilepsia Open

Species referenced: Xenopus laevis
Genes referenced: kcnq1 kcnq2 kcnq3 prrt2
GO keywords: potassium channel activity

Disease Ontology terms: benign familial neonatal epilepsy [+]

Article Images: [+] show captions
References [+] :
Adams, Synaptic inhibition of the M-current: slow excitatory post-synaptic potential mechanism in bullfrog sympathetic neurones. 1983, Pubmed