Long-term downregulation of SCN8A in mouse models of developmental and epileptic encephalopathy II

De novo mutations of the voltage-gated sodium channel SCN8A cause severe developmental and epileptic encephalopathy (DEE). Since pathogenic variants have gain-of-function effects on SCN8A activity, reduction of SCN8A expression is an effective therapeutic strategy. We previously described an antisense oligonucleotide (ASO) that delays seizure onset in a mouse model of SCN8A-DEE when administered at postnatal day 2. To investigate the potential effectiveness of post-onset ASO treatment, we first examined the extent of differential gene expression in hippocampus during the pre-onset period. Hippocampal single-nucleus RNA-sequencing detected only minor expression changes after the two month pre-seizure period. ASO treatments that were initiated after seizure onset were protective in the Scn8a mutant mice during the 12 month observation period. As an alternative treatment for down-regulation of Scn8a, we administered a single dose of an AAV10 virus expressing Scn8a shRNA. The viral shRNA was protective against seizures and lethality during the 12 month observation period. These data indicate that reduction of SCN8A expression, either by repeated administration of ASO or a single dose of shRNA virus, may be effective for longterm control of SCN8A-DEE.电压门控钠通道(voltage-gated sodium channel)SCN8A的新发突变可引发严重的发育性癫痫性脑病(developmental and epileptic encephalopathy, DEE)。鉴于致病变异体对SCN8A活性具有功能获得性效应，降低SCN8A的表达是一种有效的治疗策略。本团队此前曾报道一种反义寡核苷酸(antisense oligonucleotide, ASO)，在出生后第2天给药时，可延缓SCN8A-DEE小鼠模型的癫痫发作起始。为探究发作后ASO治疗的潜在有效性，我们首先检测了发作前阶段海马体中的差异基因表达水平。海马体单细胞核RNA测序(single-nucleus RNA-sequencing)结果显示，在为期2个月的癫痫发作前阶段后，仅观察到轻微的基因表达变化。在癫痫发作起始后启动的ASO治疗，在为期12个月的观察期内对Scn8a突变小鼠具有保护作用。作为下调Scn8a表达的替代治疗方案，我们给予了单剂表达Scn8a短发夹RNA(shRNA)的AAV10病毒(AAV10 virus)。该病毒介导的shRNA在12个月的观察期内，可对抗癫痫发作与致死性事件。上述数据表明，无论是通过反复给予ASO，还是单次给予shRNA病毒以降低SCN8A的表达，均可有效长期控制SCN8A-DEE。