SCN8A epileptic encephalopathy mutations produce hyperexcitability by differentially modulating persistent and resurgent sodium current in human iPSC-derived excitatory cortical neurons.
Abstract number :
1.011
Submission category :
1. Translational Research: 1A. Mechanisms / 1A2. Epileptogenesis of genetic epilepsies
Year :
2017
Submission ID :
348480
Source :
www.aesnet.org
Presentation date :
12/2/2017 5:02:24 PM
Published date :
Nov 20, 2017, 11:02 AM
Authors :
Luis F. Lopez-Santiago, University of Michigan Medical School; Yukun Yuan, University of Michigan Medical School; Andrew M. Tidball, University of Michigan Medical School; Jack M. Parent, University of Michigan; and Lori L. Isom, University of Michigan Me
Rationale: SCN8A encodes the voltage-gated sodium channel (VGSC) Nav1.6, the most abundant VGSC in brain. De novo mutations in SCN8A have recently been found to cause an early infantile epileptic encephalopathy, EIEE13. More than 100 EIEE13 patients have been identified, with disease typically manifesting as intractable seizures, intellectual disability and high rates of Sudden Unexpected Death in Epilepsy (SUDEP). Methods: We obtained dermal fibroblasts from three EIEE13 patients with SCN8A mutations and compared them to non-epileptic controls. Fibroblasts were reprogrammed into induced pluripotent stem cells (iPSCs) and then differentiated into excitatory cortical-like neurons. The electrophysiological properties of these cells were analyzed using whole-cell patch-clamp recordings. Results: We observed an increase in the percentage of the peak transient sodium current density that is persistent, or non-inactivating, in two of the three EIEE13 patients (control, 4.00±0.70%; patient 1, 5.75±0.60%, p=007; patient 2, 7.10±1.24%, p=0.026; patient 3, 3.65±0.44%. p=0.981), as well as decreased peak transient sodium current density in neurons from one of the patients (-226±39 pA/pF in control; -134±12 pA/pF (p=0.036) for patient 1; -179±36 pA/pF (p=0.548) for patient 2, -190±28 pA/pF (p=0.705) for patient 3). Analysis of resurgent sodium current showed a 10-fold increase in neurons from EIEE13 patient 3 (-0.74±0.32 pA/pF in control; -7.32±1.06 pA/pF for patient 3), but not in the other two EIEE13 patients. There were no significant changes in voltage dependent properties of any patient neurons compared with controls. Action potential recordings showed hyperexcitability (spontaneous firing) in all three patient neuronal populations compared with control neurons. In addition, neurons from patient 3 also showed early afterdepolarization (EAD)-like waveforms. Conclusions: These data suggest that increased persistent sodium current or resurgent current may underlie pathogenic mechanisms in EIEE13. Funding: Supported by NIH U01 NS090364 and R01NS088571 to LLI and JMP.
Translational Research