Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China.
School of Life Science and Technology, Xinxiang Medical University, Xinxiang, China.
Epilepsia. 2021 Feb;62(2):517-528. doi: 10.1111/epi.16805. Epub 2021 Jan 5.
Mutations of the cyclin-dependent kinase-like 5 (CDKL5) gene cause severe neurodevelopmental disorders characterized by intractable epilepsy, intellectual disability, and autism. Multiple mouse models generated for mechanistic studies have exhibited phenotypes similar to some human pathological features, but none of the models has developed one of the major symptoms affecting CDKL5 deficiency disorder (CDD) patients: intractable recurrent seizures. As disrupted neuronal excitation/inhibition balance is closely associated with the activity of glutamatergic and γ-aminobutyric acidergic (GABAergic) neurons, our aim was to study the effect of the loss of CDKL5 in different types of neurons on epilepsy.
Using the Cre-LoxP system, we generated conditional knockout (cKO) mouse lines allowing CDKL5 deficiency in glutamatergic or GABAergic neurons. We employed noninvasive video recording and in vivo electrophysiological approaches to study seizure activity in these Cdkl5 cKO mice. Furthermore, we conducted Timm staining to confirm a morphological alteration, mossy fiber sprouting, which occurs with limbic epilepsy in both human and mouse brains. Finally, we performed whole-cell patch clamp in dentate granule cells to investigate cell-intrinsic properties and synaptic excitatory activity.
We demonstrate that Emx1- or CamK2α-derived Cdkl5 cKO mice manifest high-frequency spontaneous seizure activities recapitulating the epilepsy of CDD patients, which ultimately led to sudden death in mice. However, Cdkl5 deficiency in GABAergic neurons does not generate such seizures. The seizures were accompanied by typical epileptic features including higher amplitude spikes for epileptiform discharges and abnormal hippocampal mossy fiber sprouting. We also found an increase in spontaneous and miniature excitatory postsynaptic current frequencies but no change in amplitudes in the dentate granule cells of Emx1-cKO mice, indicating enhanced excitatory synaptic activity.
Our study demonstrates that Cdkl5 cKO mice, serving as an animal model to study recurrent spontaneous seizures, have potential value for the pathological study of CDD-related seizures and for therapeutic innovation.
细胞周期蛋白依赖性激酶样 5（CDKL5）基因突变导致严重的神经发育障碍，其特征为难治性癫痫、智力障碍和自闭症。为了进行机制研究而生成的多种小鼠模型表现出与一些人类病理特征相似的表型，但没有一种模型出现影响 CDKL5 缺乏症（CDD）患者的主要症状之一：难治性复发性癫痫。由于神经元兴奋/抑制平衡的破坏与谷氨酸能和γ-氨基丁酸能（GABA 能）神经元的活性密切相关，我们的目的是研究 CDKL5 在不同类型神经元中的缺失对癫痫的影响。
我们使用 Cre-LoxP 系统生成条件性敲除（cKO）小鼠系，允许谷氨酸能或 GABA 能神经元中 CDKL5 缺失。我们采用非侵入性视频记录和体内电生理方法研究这些 Cdkl5 cKO 小鼠的癫痫发作活动。此外，我们进行 Timm 染色以确认在人类和小鼠大脑中的边缘性癫痫中发生的形态改变，苔藓纤维发芽。最后，我们在齿状回颗粒细胞中进行全细胞膜片钳记录以研究细胞内特性和突触兴奋性活动。
我们证明 Emx1-或 CamK2α衍生的 Cdkl5 cKO 小鼠表现出高频自发性癫痫发作，重现了 CDD 患者的癫痫发作，最终导致小鼠突然死亡。然而，GABA 能神经元中的 Cdkl5 缺失不会产生这种癫痫发作。癫痫发作伴随着典型的癫痫特征，包括癫痫样放电的更高幅度尖峰和海马苔藓纤维发芽异常。我们还发现 Emx1-cKO 小鼠的齿状回颗粒细胞中自发性和微小兴奋性突触后电流频率增加，但幅度没有变化，表明兴奋性突触活性增强。
我们的研究表明，Cdkl5 cKO 小鼠作为研究复发性自发性癫痫的动物模型，对于 CDD 相关癫痫的病理研究和治疗创新具有潜在价值。
