9 / 12 / 2019
Christopher Patzke, Ph.D.
条件敲除方法： Cre / Lox技术在人类神经元中的应用
Dr. Minmin Luo
使用人类多能干细胞来模拟人类疾病已成为生物医学领域的新标准。为此，许多研究采用体外培养的患者来源的体细胞以模拟人类病理状况。值得注意的是，人类突触与许多先天性疾病有关，因此对其功能和结构的系统性理解对于寻求治疗方法至关重要。在我的演讲中，我将介绍一种实验策略“条件性基因敲除法”，该方法可以对人类神经元中与疾病相关的突变进行改造。结合Cre / Lox技术，该方法使我能够研究人类疾病的分子机理，而不受遗传背景或克隆选择引起的遗传改变的影响。我构建了神经元突触关键蛋白如Munc18-1（STXBP1），L1CAM和Synapsin-1的基因敲除，这些基因分别影响突触传递、轴突发育和突触可塑性。令人惊讶的是，在Synapsin-1的研究中我们发现了人类神经元新的突触前可塑性机制： 在神经调质的刺激下， synapsins以迅速和双向依赖cAMP的方式，通过作用于下游五羟色胺和去甲肾上腺素的调质GPCR, 调控突触小泡储备池的大小。
Christopher Patzke studied Biology at the Freie Universität in Berlin and the École Normale Supérieure in Paris (1998-2004). During his PhD training and initial postdoc time (2004-2011) in the laboratory of Dr. Fritz Rathjen at the Max-Delbrück-Center in Berlin he investigated the role of cell adhesion in neuronal cells. Since January 2012, he works as a postdoctoral research associate at Stanford in the laboratory of Dr. Thomas Südhof and focuses on developing new neurobiological disease and research models by utilizing human pluripotent stem cell derived neurons.
Initially in his work, Christopher helped developing and characterizing stem cell derived human neurons generated by overexpressing a single transcription factor (Neurogenin-2). Subsequently, he sought ways of applying these induced human neurons for disease modelling. In particular, he established a truly isogenic platform by combining cre/lox technology with induced neurons. This conditional knockout approach allows to study disease-relevant candidate mutations in a controlled genetic background, because mutant and wild type cell are derived from the same cell population of healthy stem cells.
He has successfully engineered heterozygous and homozygous mutant stem cell lines for Munc18-1 (STXBP1), a member of the SM-protein family, essential for synaptic vesicle fusion. Heterozygous mutations lead to a severe form of early infantile epileptic encephalopathy, namely Ohtahara Syndrome. Christopher’s work demonstrated that Munc18-1 deletions in a healthy genetic background leads to decreased synaptic transmission. Moreover, he generated conditionally hemizygous mutants for L1CAM and Synapsin-1, two X-chromosomal genes linked to severe intellectual disabilities and epilepsy. In the case of L1CAM, an immunoglobulin-domain containing cell adhesion molecule, he was able to reveal a new phenotype in loss-of-function mutant neurons: The decreased excitability of these neurons, due to an impaired axonal development, represents an underappreciated phenotype, which likely contributes to the disease pathology of L1-syndrome patients. In his main project, the Synapsin-1 conditional knockout, Christopher can compellingly show, that the presynaptic phosphoprotein Synapsin acts down-stream of neuromodulators such as Norepinephrine or Serotonin, as a bidirectional cAMP-dependent regulator of the synaptic vesicle pool size.
Combining technologies, such as genetic engineering, cell imaging, biochemistry, brain organoid cultures and physiology, he generates and studies Cre/Lox conditionally mutated human neurons, allowingin vitro analyses of cellular processes independent of the genetic background or genetic alterations induced by clonal selection. His main goal is to answer questions about the molecular underpinnings of human biology and pathology mechanisms in neurodevelopmental and neuropsychiatric disorders.