Modelling human brain circuitry in patients with KCNQ2-Developmental Epileptic Encephalopathy using induced pluripotent stem cells
Date
2023-10-16Author
Stewart, Rachel
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Abstract
Mutations (pathogenic variants) in KCNQ2, which encode the voltage-dependent K+ channel
Kv7.2 (responsible for neuronal M-current) can cause developmental epileptic
encephalopathy (DEE), a disorder presenting with severe early-onset seizures and impaired
neurodevelopment. Treatment of this disorder is very difficult because the effect of
KCNQ2 mutations on neurodevelopment is still largely unknown. In this study, we generated
patient-specific iPSCs from 4 patients harbouring different KCNQ2-DEE loss-of-function,
mutations: R213Q, F261L, A265T and A294V, and 4 sibling controls which were subsequently
differentiated into excitatory cortical neurons to model the disease in vitro. We performed
multi-electrode array (MEA) recordings of cortical neurons with the KCNQ2-DEE pathogenic
variants F261L, A265T and A294V and found that for each mutation, neurons were
hyperexcitable and displayed a burst-suppression firing pattern that is reminiscent of the
interictal electroencephalography pattern seen in patients (burst suppression). We chose to
focus on the pathogenic variant A265T for further functional analysis and found that A265T
neurons displayed functional enhancement of Na+ channels and Ca2+ activated K+ channels
while also exhibited altered spontaneous Ca2+ transients via Ca2+ imaging experiments. We
showed that the Na+ channel blocker carbamazepine, and the K+
channel opener retigabine,
were capable of reducing the phenotype in patient neurons, albeit not to the level of controls.
Our data shows for the first time that patient-specific iPSC-derived cortical neurons
harbouring the pathogenic variants F261L, A265T and A294V are hyperexcitable and display
an irregular firing pattern compared to sibling controls. Moreover, we have generated a
patient-specific disease model which is invaluable for drug testing and discovery with great
potential for precision medicine.