Tuberous Sclerosis Complex (TSC) is a disease caused by autosomal dominant mutations in the TSC1 or TSC2 genes, and is characterized by tumor susceptibility, brain lesions, seizures and behavioral impairments. The TSC1 and TSC2 genes encode proteins forming a complex (TSC), which is a major regulator and suppressor of mammalian target of rapamycin complex 1 (mTORC1), a signaling complex that promotes cell growth and proliferation. TSC1/2 loss of heterozygosity (LOH) and the subsequent complete loss of TSC regulatory activity in null cells causes mTORC1 dysregulation and TSC-associated brain lesions or other tissue tumors. However, it is not clear whether TSC1/2 heterozygous brain cells are abnormal and contribute to TSC neuropathology. To investigate this issue, we generated induced pluripotent stem cells (iPSCs) from TSC patients and unaffected controls, and utilized these to obtain neural progenitor cells (NPCs) and differentiated neurons in vitro. These patient-derived TSC2 heterozygous NPCs were delayed in their ability to differentiate into neurons. Patient-derived progenitor cells also exhibited a modest activation of mTORC1 signaling downstream of TSC, and a marked attenuation of upstream PI3K/AKT signaling. We further show that pharmacologic PI3K or AKT inhibition, but not mTORC1 inhibition, causes a neuronal differentiation delay, mimicking the patient phenotype. Together these data suggest that heterozygous TSC2 mutations disrupt neuronal development, potentially contributing to the disease neuropathology, and that this defect may result from dysregulated PI3K/AKT signaling in neural progenitor cells.

结节性硬化症（TSC）是由TSC1或TSC2基因的常染色体显性突变引起的疾病，其特征是肿瘤易感性，脑损伤，癫痫发作和行为障碍。的TSC1和TSC2基因编码形成复合物（TSC），这是一个主要调节剂和雷帕霉素复合物1（mTORC1的）的哺乳动物靶的抑制剂，信号复合物，促进细胞生长和增殖的蛋白。TSC1 / 2杂合性（LOH）丧失以及随后空细胞中TSC调节活性的完全丧失会导致mTORC1失调以及与TSC相关的脑损伤或其他组织肿瘤。但是，尚不清楚是否TSC1 / 2杂合子脑细胞异常并促成TSC神经病理学。为了调查此问题，我们从TSC患者和未受影响的对照中产生了诱导性多能干细胞（iPSC），并利用它们来获得神经祖细胞（NPC）和体外分化的神经元。这些患者来源的TSC2杂合NPC分化为神经元的能力有所延迟。患者来源的祖细胞还表现出TSC下游mTORC1信号传导的适度激活，以及上游PI3K / AKT信号传导的显着衰减。我们进一步表明，药理学PI3K或AKT抑制作用而非mTORC1抑制作用引起神经元分化延迟，模仿患者的表型。这些数据加在一起表明杂合的TSC2 突变破坏神经元发育，可能导致疾病神经病理，并且这种缺陷可能是由于神经祖细胞中PI3K / AKT信号传导失调所致。