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January 26, 2026Epilepsia

Strong gain-of-function KCNQ2 variants link to cognitive impairment despite similar seizure control.

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Why the study?

Pathogenic KCNQ2 variants cause a spectrum of disorders, but their clinical progression, underlying pathogenesis, and the specific role of gain-of-function variants in neurodevelopmental impairment required delineation.

Population

90 patients in a Chinese cohort with KCNQ2-related disorders

Comparison

SeL(F)NIE vs DEEs vs NDDs subgroups

Design

Longitudinal cohort study with integrated functional analyses

Key result

Strong gain-of-function KCNQ2 variants were associated with significant cognitive impairment, despite comparable seizure control between NDDs and SeL(F)NIE subgroups (96% vs 100%).

Authors

JXJuan XiongHDHaolin DuanBLBo Li

Discussion

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Overview

Strong GoF KCNQ2 variants may warrant cognitive monitoring beyond seizure control; leaves open targeted therapies in NDDs.

Key Points

  • This study aimed to investigate the clinical progression and underlying mechanisms of cognitive impairment associated with KCNQ2-related disorders.
  • Conducted a longitudinal analysis of a Chinese cohort with 90 patients having KCNQ2-related disorders.
  • Classified patients into subgroups including SeL(F)NIE, DEEs, and NDDs.
  • Performed clinical phenotyping and functional analysis using electrophysiology and biochemistry on five missense variants.
  • Examined both homomeric and heteromeric channel assemblies.
  • The NDDs group showed significant cognitive impairment despite comparable seizure control to SeL(F)NIE (96% vs 100%).
  • All deceased patients were from the DEEs group (8/90).
  • Identified a spectrum of variants from loss-of-function (LoF) to gain-of-function (GoF) types.
  • Strong GoF variants (P335A/L) were linked to insensitivity to PIP2 regulation and cognitive dysfunction.
  • Defined novel strong GoF KCNQ2 variants that differ mechanistically and phenotypically from established variants.

Study Design

Type

Cohort (n=90)

Structured PICO

P
Population
90 Chinese patients with KCNQ2-related disorders, classified into SeL(F)NIE, DEEs, and NDDs subgroups, followed longitudinally.
E
Exposure
Functional analyses (electrophysiology, biochemistry) of five missense variants in homomeric and heteromeric (with Kv7.3/Kv7.5) channel assemblies.
O
Outcome
Clinical progression and underlying pathogenesis, specifically the role of gain-of-function (GoF) variants in neurodevelopmental impairment.

Main Result

Absolute Event Rate: 96% vs 100%

Clinical outcomes in KCNQ2-related disorders depend on the functional consequence of the variant (LoF vs GoF) and its behavior in heteromeric complexes, with strong GoF variants driving cognitive dysfunction.

Cite This Study

Xiong et al. (2026) conducted a cohort in KCNQ2-related disorders (n=90). KCNQ2 variants (gain-of-function vs loss-of-function) vs. Different variant types / SeL(F)NIE subgroup was evaluated on Seizure control (NDDs vs SeL(F)NIE). Strong gain-of-function KCNQ2 variants were associated with significant cognitive impairment, despite comparable seizure control between NDDs and SeL(F)NIE subgroups (96% vs 100%).

synapsesocial.com/papers/69770413722626c4468e912ehttps://doi.org/10.1002/epi.70075
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