Authors :
Presenting Author: Huijie Feng, PhD – Children's Hospital of Philadelphia
Martin Gunthorpe, PhD – Autifony Therapeutics Limited; Leah Deflitch, BS – Children's Hospital of Philadelphia; Ala Somarowthu, PhD – Children's Hospital of Philadelphia; Charles Large, PhD – Autifony Therapeutics Limited; Ethan Goldberg, MD, PhD – Children's Hospital of Philadelphia
Rationale:
A recurrent heterozygous variant c.959G >A (p.Arg320His) in KCNC1 causes progressive myoclonus epilepsy type 7 (EPM7), characterized by epilepsy, myoclonus, and ataxia. KCNC1 encodes the voltage-gated potassium (K+) channel subunit Kv3.1; Kv3.1-containing channels are expressed in defined subsets of brain neurons that fire at high frequency as determined by the unique biophysical properties of Kv3 channels. The Arg320His variant exerts a loss of Kv3.1 function via dominant negative action. Previously, we demonstrated that the complex features of EPM7 correlate with the dysfunction of Kv3.1-expressing neurons in distributed brain regions in a novel mouse model of EPM7, Kcnc1-p.Arg320His/+ (H/+) mice, and investigated the therapeutic potential of a Kv3 channel positive modulator, AUT00206. We demonstrated effects of AUT00206 on variant Kv3.1 in vitro in heterologous (HEK-293T) cells, on the excitability of Kv3.1-expressing cerebellar granule cells in acute brain slice, and on impaired performance on the Rotarod and pentylenetetrazol (PTZ) seizure threshold assay in H/+ mice in vivo. Here, we investigate the translational potential of a more potent Kv3 channel-positive modulator, AUT00201, that is currently under investigation as a therapeutic in patients with EPM7. Methods:
We tested the effect of AUT00201 at various concentrations on Kv3.1-expressing cerebellar granule neurons in acute brain slices prepared from H/+ and age-matched wild-type littermate control mice. The effects of AUT00201 on motor function and propensity to seizure in these mice was assessed
in vivo using the accelerated Rotarod test and pentylenetetrazol (PTZ) kindling test, respectively. In addition, we explored the efficacy of AUT00201 to raise the threshold for acute PTZ-induced seizures in wild-type mice. To assess the activity of Kv3.1-expressing parvalbumin-positive fast-spiking GABAergic interneurons (PV-INs), we employed 2-photon calcium imaging in mouse neocortex
in vivo.
Results:
We found that AUT00201 normalizes the excitability of cerebellar granule cells from H/+ mice to wild-type levels in acute brain slices
in vitro.
AUT00201 improved cerebellar dysfunction and propensity to seizure in vivo in a dose-dependent manner (5 mg/kg and 20 mg/kg). Furthermore, AUT00201 raised the threshold for PTZ-induced seizures in wild-type mice.Conclusions:
Kcnc1-p.Arg320H/+ mice exhibit progressive ataxia and enhanced seizure susceptibility, and hence reproduce key disease features of, and represent a model for, the study of EPM7. Impaired excitability of Kv3.1-expressing neurons in vitro and indices of cerebellar dysfunction and seizure susceptibility in vivo could be ameliorated with the potent Kv3-channel modulator AUT00201, which may demonstrate therapeutic potential for the treatment of human patients with EPM7.
Funding:
National Ataxia Foundation Postdoctoral Fellowship Award (H.F.); The Children’s Hospital of Philadelphia IDDRC New Program Development Award via NIH NINDS P50 HD105354 (E.M.G.); NIH NINDS NS122887 (E.M.G.); Autifony Therapeutics, Limited. (E.M.G.). We also acknowledge the support of the NIH NINDS Epilepsy Therapy Screening Program (ETSP) for generation of the indicated data.