Pathophysiology of DYT1 dystonia: Targeted Mouse Models

肌张力障碍是一种运动障碍，其特征在于持续或间歇性肌肉收缩， 不正常的，经常重复的动作或姿势。DYT1早发性全身性肌张力障碍是最常见的 遗传性肌张力障碍中的常见类型。大多数受DYT1肌张力障碍影响的个体都有一个共同的特征， 位于DYT1或TOR1A基因外显子5的三核苷酸缺失（ΔGAG），导致谷氨酸缺失 torsinA的氨基酸残基（torsinA Δ E）。症状从四肢开始，然后变得普遍。 受影响的人可能严重残疾，需要使用轮椅。扭转蛋白A的条件性敲除 在小鼠中的研究表明，DYT 1肌张力障碍的发病机制涉及多个脑区和细胞类型。 DYT1和其他肌张力障碍的这些和其他病理生理学研究到目前为止支持电路或网络 肌张力障碍发病机制的模型。然而，哪些大脑区域和神经元类型在大脑中起着关键作用， 发病机制尚不清楚。纹状体多巴胺能和胆碱能系统的改变似乎起着重要作用。 在DYT 1肌张力障碍的病理生理学中起关键作用。纹状体胆碱能的多巴胺能调节 在包括DYT 1肌张力障碍的多种肌张力障碍模型中，中间神经元（ChI）发生改变。是否扭转 纹状体ChI对纹状体胆碱能功能障碍具有细胞自主作用尚不清楚。初步研究 的DYT 1肌张力障碍的条件性敲入（KI）小鼠模型显示多巴胺能和纹状体中棘 在DYT 1肌张力障碍的发病机制中，MSNs而不是ChI起着至关重要的作用。然而，如何折磨 在MSN和多巴胺能神经元中导致肌张力障碍是未知的。这些未知因素阻碍了 为DYT1患者开发有效的治疗方法，特别是基于CRISPR的基因靶向治疗， 反义寡核苷酸或小发夹RNA。我们研究的广泛、长期目标是：1） 确定torsinA的功能作用和torsinA β E导致早发性肌张力障碍的机制，2） 开发新的有效的治疗方法。该应用程序的具体目标是生成和 分析五系条件性KI小鼠以了解纹状体多巴胺能系统和MSNs的作用 DYT 1肌张力障碍的发病机制。我们假设torsinA在多巴胺能神经元和MSNs中表达， 而不是ChIs，导致这些神经元的异常放电，MSNs中D1R和D2R的减少，纹状体 多巴胺释放，受损皮质纹状体LTD，改变直接和间接途径，并最终持续 肌张力障碍所特有的肌肉收缩和共同收缩。目标1将生成条件 MSN KI小鼠限于直接途径、间接途径或两者，并确定其表型。在目标2中， 我们将在多巴胺能神经元或ChIs中特异性地引入torsinA β E，并确定其与肌张力障碍相关的 表型成功完成拟议的研究将大大增加我们的了解 DYT 1肌张力障碍的病理生理学，并有助于开发肌张力障碍的新型靶向治疗方法 患者

Dystonia is a movement disorder characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive, movements or postures. DYT1 early-onset generalized dystonia is the most common type among the genetic dystonias. Most of the individuals affected by DYT1 dystonia share a trinucleotide deletion (ΔGAG) located in exon 5 of DYT1 or TOR1A gene, leading to a loss of a glutamate amino acid residue for torsinA (torsinA∆E). The symptoms start from limbs and then become generalized. Affected individuals could be seriously disabled and need to use a wheelchair. Conditional knockout of torsinA in mice points to the involvement of multiple brain regions and cell types in the pathogenesis of DYT1 dystonia. These and other pathophysiological studies of DYT1 and other dystonias so far support a circuit or network model of dystonia pathogenesis. However, which brain region and neuronal types play a critical role in pathogenesis is unclear. Alterations of both the striatal dopaminergic and cholinergic systems appear to play a critical role in the pathophysiology of DYT1 dystonia. Dopaminergic modulation of striatal cholinergic interneurons (ChIs) is altered in multiple dystonia models that include DYT1 dystonia. Whether torsinA∆E in striatal ChIs has the cell-autonomous effect on striatal cholinergic dysfunction is not known. Preliminary studies of conditional knockin (KI) mouse models of DYT1 dystonia revealed dopaminergic and striatal medium spiny neurons (MSNs), but not ChIs, play a vital role in the pathogenesis of DYT1 dystonia. However, how torsinA∆E in MSNs and dopaminergic neurons lead to dystonia is unknown. These unknowns impede the progress in developing effective treatment for DYT1 patients, especially gene-based targeted therapy with CRISPR, antisense oligonucleotides, or small hairpin RNA. The broad, long-term objective of our research is 1) to determine the functional role of torsinA and the mechanism by which torsinA∆E leads to early-onset dystonia, 2) to develop novel and effective therapeutic treatment. The specific goal of this application is to generate and analyze five lines of conditional KI mice to understand the role of the striatal dopaminergic system and MSNs in the pathogenesis of DYT1 dystonia. We hypothesize that torsinA∆E in dopaminergic neurons and MSNs, but not ChIs, leads to abnormal firing of these neurons, decreased D1R and D2R in MSNs, altered striatal dopamine release, impaired corticostriatal LTD, altered direct and indirect pathways, and ultimately sustained muscle contractions and co-contractions that are characteristic of dystonia. Aim 1 will generate conditional MSN KI mice restricted to direct pathway, indirect pathway, or both and determine their phenotype. In Aim 2, we will introduce torsinA∆E specifically in dopaminergic neurons or ChIs and determine their dystonia-related phenotypes. The successful completion of the proposed research will significantly increase our understanding of the pathophysiology of DYT1 dystonia and aid the development of novel targeted treatments for dystonia patients.