Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA; Division of Epilepsy and Clinical Neurophysiology and Epilepsy Genetics Program, Boston Children's Hospital, Boston, MA 02115, USA; Department of Neurology, Harvard Medical School, Boston, MA 02115, USA.
Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA.
Neurobiol Dis. 2018 Mar;111:91-101. doi: 10.1016/j.nbd.2017.12.010. Epub 2017 Dec 20.
DEPDC5 is a newly identified epilepsy-related gene implicated in focal epilepsy, brain malformations, and Sudden Unexplained Death in Epilepsy (SUDEP). In vitro, DEPDC5 negatively regulates amino acid sensing by the mTOR complex 1 (mTORC1) pathway, but the role of DEPDC5 in neurodevelopment and epilepsy has not been described. No animal model of DEPDC5-related epilepsy has recapitulated the neurological phenotypes seen in patients, and germline knockout rodent models are embryonic lethal. Here, we establish a neuron-specific Depdc5 conditional knockout mouse by cre-recombination under the Synapsin1 promotor. Depdc5-Syn1 (Depdc5cc+) mice survive to adulthood with a progressive neurologic phenotype that includes motor abnormalities (i.e., hind limb clasping) and reduced survival compared to littermate control mice. Depdc5cc+ mice have larger brains with increased cortical neuron size and dysplastic neurons throughout the cortex, comparable to the abnormal neurons seen in human focal cortical dysplasia specimens. Depdc5 results in constitutive mTORC1 hyperactivation exclusively in neurons as measured by the increased phosphorylation of the downstream ribosomal protein S6. Despite a lack of increased mTORC1 signaling within astrocytes, Depdc5cc+ brains show reactive astrogliosis. We observed two Depdc5cc+ mice to have spontaneous seizures, including a terminal seizure. We demonstrate that as a group Depdc5cc+ mice have lowered seizure thresholds, as evidenced by decreased latency to seizures after chemoconvulsant injection and increased mortality from pentylenetetrazole-induced seizures. In summary, our neuron-specific Depdc5 knockout mouse model recapitulates clinical, pathological, and biochemical features of human DEPDC5-related epilepsy and brain malformations. We thereby present an important model in which to study targeted therapeutic strategies for DEPDC5-related conditions.
DEPdc5 是一种新发现的与癫痫相关的基因，与局灶性癫痫、脑畸形和癫痫不明原因猝死 (SUDEP) 有关。在体外，DEPdc5 负调控 mTOR 复合物 1 (mTORC1) 通路的氨基酸感应，但 DEPDC5 在神经发育和癫痫中的作用尚未描述。没有 DEPDC5 相关癫痫的动物模型能够重现患者中观察到的神经表型，并且种系敲除啮齿动物模型是胚胎致死的。在这里，我们通过 Synapsin1 启动子下的 Cre 重组建立了神经元特异性 Depdc5 条件性敲除小鼠。Depdc5-Syn1 (Depdc5cc+) 小鼠存活至成年，表现出进行性神经表型，包括运动异常（即后肢紧握）和与同窝对照小鼠相比生存率降低。Depdc5cc+ 小鼠的大脑较大，皮质神经元大小增加，皮质各处存在发育不良的神经元，与人类局灶性皮质发育不良标本中异常神经元相似。Depdc5 导致 mTORC1 持续激活，这仅在神经元中被测量到下游核糖体蛋白 S6 的磷酸化增加。尽管星形胶质细胞中没有增加的 mTORC1 信号，但 Depdc5cc+ 大脑显示出反应性星形胶质增生。我们观察到两只 Depdc5cc+ 小鼠发生自发性癫痫，包括一次终末性癫痫。我们证明，作为一个整体，Depdc5cc+ 小鼠的癫痫发作阈值降低，这表现在化学惊厥剂注射后癫痫发作潜伏期缩短和戊四氮诱导的癫痫发作死亡率增加。总之，我们的神经元特异性 Depdc5 敲除小鼠模型再现了人类 DEPDC5 相关癫痫和脑畸形的临床、病理和生化特征。因此，我们提出了一个重要的模型，可用于研究针对 DEPDC5 相关疾病的靶向治疗策略。
