Human Huntington's Disease iPSC-derived cortical neurons display altered transcriptomics, morphology and electrophysiological maturation

Huntington's disease (HD) is a neurodegenerative disease caused by an expanded CAG repeat in the Huntingtin (HTT) gene. Induced pluripotent stem cell (iPSC) models of HD provide an opportunity to study the mechanisms underlying disease pathology in patient tissues relevant to disease. Murine studies have demonstrated that HTT is intricately involved in corticogenesis, and mutant (mt) HTT cannot compensate for the loss of non-CAG-expanded HTT. However, the critical effect of mtHTT in human corticogenesis has not yet been specifically explored and due to inherent differences in cortical development and timing between humans and mice. We therefore differentiated HD and non-diseased iPSCs into functional cortical neurons. While HD patient iPSCs can be successfully differentiated towards a cortical fate in culture, the resulting neurons display transcriptomic, morphological and functional phenotypes indicative of altered neurodevelopment. This is the first demonstration of altered corticogenesis from HD human patient cells, further supporting the potential neurodevelopmental aspect of HD. Overall design: HD patients with an expanded CAG HTT allele of 180 (CS97iHD180n), 109 (CS09iHD109n), or 77 CAG repeats (CS77iHD77n) and from three non-HD “controls” with 33 (CS83iCTR33n), 21 (CS00iCTR21n), or 18 (CS25iCTR18n) repeat CAG alleles. iPSCs were differentiated towards a cortical fate as described in Shi et al. (doi: 10.1038/nprot.2012.116.) for 0 (iPSC colonies), 60, 80, 100, 130 days.

亨廷顿舞蹈症（Huntington's disease, HD）是一类由亨廷顿蛋白（Huntingtin, HTT）基因CAG三核苷酸重复序列异常扩增所引发的神经退行性疾病。基于HD的诱导多能干细胞（induced pluripotent stem cell, iPSC）模型，为在疾病相关的患者源性组织中解析疾病病理发生的分子机制提供了可行途径。既往小鼠研究证实，HTT在大脑皮质发生过程中发挥着精密且关键的调控作用，且突变型（mutant, mt）HTT无法代偿非CAG扩增型HTT的功能缺失。然而，由于人类与小鼠在皮质发育模式及时间进程上存在固有差异，mtHTT在人类皮质发生中的核心调控效应迄今尚未得到专门探究。为此，本研究将HD患者及健康非患病个体的iPSC定向诱导分化为功能性皮质神经元。尽管HD患者iPSC可在体外培养体系中成功定向分化为皮质谱系细胞，但所得神经元在转录组、形态学及功能层面均呈现出神经发育异常的表型。本研究首次证实HD患者来源细胞的皮质发生过程存在异常，进一步支撑了HD存在潜在神经发育异常维度的学术观点。实验设计：纳入携带HTT基因CAG重复序列分别为180次（CS97iHD180n）、109次（CS09iHD109n）及77次的扩增等位基因的HD患者，以及3名非HD健康对照个体，其HTT基因CAG重复序列分别为33次（CS83iCTR33n）、21次（CS00iCTR21n）及18次（CS25iCTR18n）。按照Shi等人（doi: 10.1038/nprot.2012.116）报道的实验方案，将iPSC定向诱导为皮质谱系细胞，诱导时长分别设置为0天（即未分化的iPSC集落）、60天、80天、100天及130天。