Pathophysiology of DYT1 dystonia: Targeted Mouse Models

肌张力障碍是一种运动障碍，其特征是持续性或间歇性肌肉收缩导致 反常动作不正常的，经常重复的动作或姿势DYT1早发性全身性肌张力障碍最多 遗传性牙张力障碍中常见的类型。大多数受DYT1肌张力障碍影响的个体都有相同的 位于DYT1或Δ基因第5外显子的三核苷酸缺失(DYT1GAG)导致谷氨酸丢失 TorsinA的氨基酸残基(TorsinA∆E)。症状从四肢开始，然后变得普遍。 受影响的人可能是严重残疾，需要使用轮椅。扭力A的条件性击倒 研究表明，DYT1肌张力障碍的发病机制涉及多个脑区和细胞类型。 到目前为止，这些和其他对DYT1和其他牙列障碍的病理生理学研究支持一种回路或网络 肌张力障碍发病机制模型。然而，哪些脑区和神经元类型在 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在 在DYT1肌张力障碍的病理生理学中的关键作用。纹状体胆碱能的多巴胺能调节 中间神经元(CHI)在包括DYT1肌张力障碍在内的多种肌张力障碍模型中发生改变。TorsinA∆E是否进入 纹状体CHIS对纹状体胆碱能功能障碍的细胞自主作用尚不清楚。初步研究 条件性敲击(KI)小鼠DYT1肌张力障碍模型显示多巴胺能和纹状体中棘 神经元(MSN)，而不是CHI，在DYT1肌张力障碍的发病机制中起重要作用。然而，TorsinA∆E如何 在MSN和多巴胺能神经元中导致肌张力障碍的原因尚不清楚。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Torsin A的功能作用以及Torsin A∆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。此应用程序的特定目标是生成和 分析5株条件性Ki小鼠以了解纹状体多巴胺能系统和MSN的作用 在DYT1肌张力障碍的发病机制中起重要作用。我们假设在多巴胺能神经元和MSN中TorsinA∆E，但是 非CHIS导致这些神经元的异常放电，MSN中D1R和D2R减少，纹状体改变 多巴胺释放，损害了皮质纹状体LTD，改变了直接和间接途径，并最终持续 肌肉收缩和联合收缩是肌张力障碍的特征。目标1将生成有条件的 MSN Ki小鼠被限制为直接途径、间接途径或两者兼而有之，并确定其表型。在目标2中， 我们将在多巴胺能神经元或CHI中特异性地引入TorsinA∆E，并确定它们与肌张力障碍相关 表型。拟议研究的成功完成将大大增加我们对 研究DYT1肌张力障碍的病理生理机制，并帮助开发新的针对肌张力障碍的靶向治疗方法 病人。

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.