Molecular characterization of TUBB4 mutations

我们最近发现β微管蛋白4 （TUBB4或TUBB4A）基因突变是DYT4肌张力障碍的原因。DYT4的特点是突出的低声发音障碍和广泛性张力障碍。随着肌张力障碍中微管蛋白基因突变的检测，一种新的途径，即细胞骨架的破坏，已经涉及肌张力障碍的病理生理学，保证功能表征。在本文中，我们旨在阐明TUBB4突变的频谱和功能后果，具体目的有以下三个：(1)为了确定由TUBB4突变引起的肌张力障碍表型的频谱，我们将对约2000名不同形式的肌张力障碍/肌张力障碍综合征患者的所有编码外显子进行测序。(2)为了确定已知和新的TUBB4突变对分子水平的影响，我们将分析三种已知和最多两种新发现的突变体和野生型TUBB4的mRNA水平、蛋白质稳定性和亚细胞定位。为此，我们将主要使用生物学相关的细胞模型。即诱导多能干细胞（iPSC）衍生的神经元，由我们的突变载体产生，以及talen校正的等基因控制系。(3)为了研究ipsc衍生神经元的神经元形态和轴突运输，我们将分析线粒体运输和神经突生长，并测试微管蛋白稳定剂对tubb4相关神经元功能障碍的拯救能力。

We recently identified mutations in the beta Tubulin 4 (TUBB4 or TUBB4A) gene as the cause of DYT4 dystonia. DYT4 is characterized by prominent whispering dysphonia and generalized dystonia. With the detection of mutations in a tubulin gene in dystonia, a novel pathway, i. e. disruption of the cytoskeleton, has been implicated in the pathophysiology of dystonia warranting functional characterization. In the present proposal, we aim to elucidate the spectrum and functional consequences of TUBB4 mutations with the following three specific aims: (1) To determine the spectrum of dystonic phenotypes caused by mutations in TUBB4, we will sequence all coding exons in ~2000 patients with different forms of dystonia/dystonic syndromes. (2) To identify the impact of known and novel mutations in TUBB4 on the molecular level, we will analyze mRNA levels, protein stability, and subcellular localization of the three known and up to two newly identified mutants and wildtype TUBB4. For this, we will primarily use a biologically relevant cell model. i.e. induced pluripotent stem cell (iPSC)-derived neurons generated from our mutation carriers, as well as TALEN-corrected isogenic control lines. (3) To study neuronal morphology and axonal transport in iPSC-derived neurons, we will analyze mitochondrial transport and neurite outgrowth and test the ability of a tubulin-stabilizing agent to rescue TUBB4-related neuronal dysfunction.