Pathophysiology of familial hemiplegic migraine: analysis of a newly generated transgenic SCN1A mouse model

家族性偏瘫偏头痛(FHM)是一种严重的常染色体显性先兆偏头痛亚型。申请人通过定位克隆的方法，鉴定了SCN1A为第三个FHM基因(FHM3；Dichgans*，Freilinger*等人)。《柳叶刀》2005)。SCN1A编码一个神经元电压门控钠通道(Nav1.1)，负责动作电位的产生和传播。以前对过度表达Nav1.1通道的细胞的研究表明，FHM患者的突变通道功能丧失(Kahlig，...，Freilinger等人)。《北京大学学报》，S，2008年)。然而，到目前为止，突变的Nav1.1在偏头痛和偏头痛先兆中的确切作用尚不清楚。为了揭示Nav1.1在偏头痛和偏头痛先兆的病理生理学中的意义，申请者通过同源重组的方法，建立了具有代表性的人类SCN1A突变(L1649Q)的敲入小鼠模型。在对转基因动物进行生化和组织学初步表征后，以下具体假设将在这个新产生的动物模型中进行验证：1.SCN1a基因敲入的动物表现出间歇性的神经功能障碍(例如偏瘫发作或癫痫发作)。敲入SCN1a基因的动物对皮层扩散性去极化(CSD)的诱导敏感性增加，CSD可能与偏头痛有关。SCN1a基因敲入动物具有神经生理学改变，可以解释神经元的高度兴奋性。Scn1aL1649Q Ki动物的多模式功能特征，特别关注偏头痛等效物和癫痫发作，2.分析突变对实验诱导的体内CSD的影响，3.通过对原代培养的Scn1aL1649QKI动物神经细胞突变的电生理学特征以及急性脑片和自发神经网络活动的分析，我们希望通过这些研究，进一步深入了解FHM和偏头痛的病理生理学，这可能为新的治疗策略的开发打开大门。我们已经获得了携带紧邻L1649(R1648H)的氨基酸突变的转基因癫痫小鼠模型。这将允许对这两种动物模型进行直接的面对面比较，旨在更好地了解偏头痛和癫痫的不同机制，即两种表型重叠的发作性神经疾病。

Familial hemiplegic migraine (FHM) is a severe autosomal-dominant subtype of migraine with aura. The applicants, by means of positional cloning, have identified SCN1A as the third FHM gene (FHM3; Dichgans*, Freilinger* et al. Lancet 2005). SCN1A encodes a neuronal voltage-gated sodium channel (Nav1.1), which is responsible for the generation and propagation of action potentials.Previous studies in cells overexpressing Nav1.1 channels with FHM-associated mutations point towards a loss-of-function of mutant channels in FHM patients (Kahlig, ..., Freilinger et al. Proc Natl Acad Sci U S A 2008). However, the precise role of mutant NaV1.1 for migraine and migraine aura remains unclear to date.To unravel the significance of NaV1.1 in the pathophysiology of migraine and migraine aura, the applicants, by means of homologous recombination, have generated a knock-in mouse model for a representative human SCN1A mutation (L1649Q).After an initial characterization of transgenic animals with respect to biochemistry and histology, the following specific hypotheses will be tested in this newly generated animal model: 1.) Scn1a knock-in animals show episodic neurological disturbances (e.g. hemiplegic attacks or epileptic seizures).2.) Scn1a knock-in animals have an increased susceptibility to the induction of cortical spreading depolarisations (CSD), the likely correlate of migraine aura.3.) Scn1a knock-in animals have neurophysiological alterations, which can explain neuronal hyperexcitability.In detail, the following investigations are planned: 1.) multimodal functional characterization of Scn1aL1649Q KI animals, focussing specifically on migraine equivalents and epileptic seizures, 2.) analysis of the effects of the mutation on experimentally induced CSD in vivo, 3.) electrophysiological characterization of the mutation in primary neuronal cell cultures from Scn1aL1649Q KI animals complemented by an analysis of acute brain slices and spontaneous neuronal network activity.By means of these investigations, we hope to gain further insight into the pathophysiology of FHM and migraine in general, which may open the door for the development of novel therapeutic strategies.Of note, mutations in Scn1a are associated also with epilepsy. We have access to a transgenic epilepsy mouse model carrying a mutation of the amino acid immediately adjacent to L1649 (R1648H). This will allow a direct head-to-head comparison of these two animal models, aiming at a better understanding of the differential mechanisms of migraine and epilepsy, i.e. two phenotypically overlapping paroxysmal neurological disorders.