Human iPSC-derived glutamatergic neurons with pathogenic KCNQ2 variants display hyperactive bursting phenotypes

Area of Science:

• Neuroscience
• Genetics
• Stem Cell Biology

Background:

• Pathogenic variants in the KCNQ2 gene are linked to severe neurological conditions, including neonatal seizures and epileptic encephalopathy.
• The precise molecular mechanisms driving these KCNQ2-related neurological phenotypes are not fully understood.
• Patient-specific neuronal models are crucial for studying these variants and developing treatments.

Purpose of the Study:

• To generate and characterize patient-specific induced pluripotent stem cell (iPSC)-derived neurons harboring distinct KCNQ2 pathogenic variants.
• To investigate the functional consequences of these KCNQ2 variants on neuronal development and network activity.
• To establish disease models for KCNQ2-related disorders suitable for drug screening.

Main Methods:

• Generated patient-specific iPSCs from fibroblasts of individuals with three different KCNQ2 pathogenic variants.
• Utilized CRISPR-Cas9 gene editing to create isogenic control lines.
• Differentiated iPSCs into glutamatergic neurons for functional and molecular analyses.
• Employed high-density microelectrode arrays for network electrophysiology.

Main Results:

• Patient-derived neurons exhibited altered neurite outgrowth and transcriptional profiles enriched in synaptic and cell adhesion pathways.
• All three KCNQ2 variant lines showed increased neuronal burst duration.
• Specific variants led to increased network connectivity and synaptic marker density.
• One variant (G256W) displayed hyperexcitable networks, which were rescued by retigabine treatment.

Conclusions:

• Patient-specific iPSC-derived neurons accurately model KCNQ2-related neurological phenotypes.
• Distinct KCNQ2 variants result in unique cellular and network dysfunctions.
• These models provide a valuable platform for identifying therapeutic interventions for KCNQ2 channelopathies.