Authors :
First Author: Sheryl Anne Vermudez, PhD – Boston Children's Hospital
Presenting Author: Gabrielle McGinty, BS – Boston Children's Hospital
Rui Lin, MS – Boston Children's Hospital; Gabrielle McGinty, BS – Boston Children's Hospital; Amanda Liebhardt, BS – Boston Children's Hospital; Benjamin Hui, BS – Boston Children's Hospital; Henry Lee, PhD – Boston Children's Hospital; Mustafa Sahin, MD, PhD – Boston Children's Hospital; Alexander Rotenberg, MD, PhD – Boston Children's Hospital
Rationale:
Dravet syndrome (DS), the most common monogenic epilepsy, is caused by haploinsufficiency of the Nav1.1 voltage-gated sodium channel, which is encoded by the Scn1a gene. Seizures in DS are commonly resistant to available anti-seizure drugs. A novel anti-seizure therapeutic target in DS is thus highly desirable. Firing rate restriction of the fast-spiking parvalbumin-positive (PV+) interneurons is a major DS pathophysiology that results from Nav1.1 deficiency. The Kv3.1 voltage-gated potassium channel is highly expressed in PV+ interneurons and is critical for the fast-spiking properties of PV+ cells. Given Kv3.1’s role in PV+ cell biology, we tested, in the DS mouse model, Scn1a+/-, 1) whether Kv3.1 expression is depressed in DS, and 2) whether Kv3.1 positive modulation suppresses seizure in DS.
Methods:
Adult Scn1a+/- mice and wild-type (WT, Scn1a+/+) littermates (n = 8 total/genotype; n = 3-9 males/genotype; n = 4-6 females/genotype) were implanted with wireless 1-channel EEG transmitters and monitored for seizure incidence for seven days. EEG recordings were analyzed for generalized tonic-clonic (GTC) seizures and interictal spectral power density across frequency bands. Mice were categorized as either non-seizing or seizing. Brains were then harvested for analysis of Kv3.1 protein expression. In a separate cohort, baseline EEG recordings in implanted Scn1a+/- mice (n = 4 total, 3 male) were first conducted. This was followed by simultaneous EEG recordings and daily intraperitoneal administration of Kv3.1 positive modulator, AUT1 or vehicle in the seizing mice. We measured changes in GTC seizure frequency and spectral power with treatment to assess the effects of Kv3.1 potentiation, and compared groups by unpaired or paired t-tests.
Results:
We did not detect sex differences in our results, so all data presented here is pooled from mixed-sex cohorts. First, we found that cortical Kv3.1 protein levels were normal in adult non-seizing Scn1a+/- mice but decreased in seizing animals compared to WT littermates (non-seizing Scn1a+/-: 95 ± 0.11%, p = 0.734 (vs WT); seizing Scn1a+/-: 78 ± 0.04%, p = 0.013 (vs WT)). Correspondingly, Kv3.1 potentiation with AUT1 treatment significantly reduced GTC seizure frequency (baseline: 8.1 ± 2.03 seizures/week; AUT1: 2.8 ± 1.87 seizures/week, p = 0.0004) and total seizure time (baseline: 334 ± 94.4 sec; AUT1: 118 ± 81.9 sec, p = 0.0009) in Scn1a+/- mice. In addition, the enhanced relative gamma power (30-90 Hz) observed in seizing Scn1a+/- animals was reduced upon AUT1 treatment (AUT1: -32 ± 2.0% of baseline, p = 0.025). The above effects diminished after AUT1 washout, suggesting phenotype reversibility.
Conclusions:
In conclusion, our findings indicate that: 1) decreased Kv3.1 activity is linked to epilepsy in DS, 2) acute Kv3.1 potentiation is anti-epileptic in DS, and 3) Kv3.1 is a promising novel target for seizure control in DS.
Funding:
This project was supported by NIMH 5T32MH112510 (SADV).