De novo heterozygous mutations in STXBP1/Munc18-1 cause early infantile epileptic encephalopathies (EIEE4, OMIM #612164) characterized by infantile epilepsy, developmental delay, intellectual disability, and can include autistic features. We characterized the cellular deficits for an allelic series of seven STXBP1 mutations and developed four mouse models that recapitulate the abnormal EEG activity and cognitive aspects of human STXBP1-encephalopathy. Disease-causing STXBP1 variants supported synaptic transmission to a variable extent on a null background, but had no effect when overexpressed on a heterozygous background. All disease variants had severely decreased protein levels. Together, these cellular studies suggest that impaired protein stability and STXBP1 haploinsufficiency explain STXBP1-encephalopathy and that, therefore, Stxbp1^+/− mice provide a valid mouse model. Simultaneous video and EEG recordings revealed that Stxbp1^+/− mice with different genomic backgrounds recapitulate the seizure/spasm phenotype observed in humans, characterized by myoclonic jerks and spike-wave discharges that were suppressed by the antiepileptic drug levetiracetam. Mice heterozygous for Stxbp1 in GABAergic neurons only, showed impaired viability, 50% died within 2–3 weeks, and the rest showed stronger epileptic activity. c-Fos staining implicated neocortical areas, but not other brain regions, as the seizure foci. Stxbp1^+/− mice showed impaired cognitive performance, hyperactivity and anxiety-like behaviour, without altered social behaviour. Taken together, these data demonstrate the construct, face and predictive validity of Stxbp1^+/− mice and point to protein instability, haploinsufficiency and imbalanced excitation in neocortex, as the underlying mechanism of STXBP1-encephalopathy. The mouse models reported here are valid models for development of therapeutic interventions targeting STXBP1-encephalopathy.

中文翻译：

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蛋白质不稳定、单倍体不足和皮质过度兴奋是 STXBP1 脑病的基础


STXBP1 /Munc18-1 的从头杂合突变会导致早期婴儿癫痫性脑病（EIEE4，OMIM #612164），其特征为婴儿癫痫、发育迟缓、智力障碍，并可能包括自闭症特征。我们描述了七个STXBP1突变等位基因系列的细胞缺陷，并开发了四种小鼠模型，以概括人类 STXBP1 脑病的异常脑电图活动和认知方面。致病的STXBP1变体在空背景下在不同程度上支持突触传递，但在杂合背景上过表达时没有影响。所有疾病变体的蛋白质水平都严重降低。总之，这些细胞研究表明，蛋白质稳定性受损和STXBP1单倍体不足解释了 STXBP1 脑病，因此， Stxbp1 ^+/-小鼠提供了有效的小鼠模型。同时视频和脑电图记录显示，具有不同基因组背景的Stxbp1 ^+/-小鼠重现了在人类中观察到的癫痫/痉挛表型，其特征是肌阵挛性抽搐和棘波放电，并被抗癫痫药物左乙拉西坦抑制。仅在 GABA 能神经元中具有Stxbp1杂合子的小鼠表现出活力受损，50% 的小鼠在 2-3 周内死亡，其余的则表现出更强的癫痫活性。 c-Fos 染色涉及新皮质区域，但不涉及其他大脑区域作为癫痫病灶。 Stxbp1 ^+/-小鼠表现出认知能力受损、多动和焦虑样行为，但社交行为没有改变。 总而言之，这些数据证明了Stxbp1 ^+/-小鼠的结构、表面和预测有效性，并指出新皮质中的蛋白质不稳定、单倍体不足和兴奋不平衡是 STXBP1 脑病的潜在机制。这里报道的小鼠模型是开发针对 STXBP1 脑病的治疗干预措施的有效模型。