Abstracts

Rationale: Dravet Syndrome (DS) has been associated with mutations in Scn1a, and constitutive Kcnq2 mutations have been found to exacerbate the DS phenotype. However, the cell-type specific influence of Kcnq2 mutations and the potential for treatment targeting Kv7.2 channels have not previously been explored. Methods: Scn1a mutant mice (Ogiwara et al, 2007) were crossed with Parvalbumin-Cre and Kcnq2-floxxed mice (Soh et al, 2014) to conditionally delete Kcnq2 from parvalbumin-expressing (PV+) interneurons in the mutant mice and maintained on a 93% C57BL/6 and 7% 129S5 background. Fluorescence immunohistochemistry (IHC) was performed using antibodies to Kv7.2 (Pierce). A Kaplan-Meier survival analysis was performed with significance calculated using the Mantel-Cox test. Mice ages P30-45 were tested with a closed-loop thermal regulator and simultaneously monitored with EEG recording over bilateral somatosensory cortex, sampling at 2 kHz. Retigabine was administered intraperitoneally at a dose of 10 mg/kg. Results: After crossing, IHC with antibodies to Kv7.2 confirmed successful recombination and deletion of Kcnq2 from PV+ interneurons. There was significantly reduced survival in DS mice with PVCre/Kcnq2fl/fl compared to PVCre/Kcnq2+/+ (p=0.0035) and no significant change in mortality for WT mice up to postnatal day 42. Baseline power between 2-300 Hz at 37.5 degrees Celcius in DS mice was not significantly different from WT mice. Thermal induction of core body temperature up to 42.5 degrees Celcius (or prior to a seizure, whichever came first) significantly increased high gamma power (72-134 Hz, maximal at 115 Hz) in DS mice (n=5) but not in WT mice (n=6). In preliminary experiments, retigabine (10 mg/kg, i.p.) prevented thermal induction of both augmented high gamma power and seizures in DS mice (n=3). Conclusions: Here we show that targeting the potassium channel Kv7.2 on both excitatory and inhibitory neurons in Dravet Syndrome may be a successful strategy, with gamma power as a potential biomarker for drug efficacy. Funding: This work was supported by the National Institute of Neurological Disorders and Stroke NINDS K08 NS096029.