MARK1 in dendritic spine neoteny

项目摘要 学习和记忆的一个关键细胞基质是树突棘的可塑性， 哺乳动物大脑中兴奋性突触输入的位点。树突棘表现出延长的突触 在人类大脑发育过程中成熟，导致成年后更长的脊椎具有更高的密度， 与啮齿动物相比。这种特殊的脊椎幼态持续被认为是高认知能力的基础。 人类的表现。然而，仍然缺乏关于分子生物学的知识。 机制，有助于树突棘幼态持续独特的人类。解决这个问题的一个方法是 问题是检查基因，显示适应性进化沿沿着人类血统。这些基因在 积极的选择压力，并可能在人类物种形成中发挥作用。特别是， 适应性进化和与神经发育障碍的遗传联系是可能 有助于人类大脑的高认知能力。到目前为止，只有少数基因 符合这两个标准。其中一个基因编码微管亲和调节激酶1（MARK 1）， 丝氨酸/苏氨酸激酶在脑内高表达。MARK 1显示了强有力的证据表明， MARK 1的单核苷酸多态性（SNP）与自闭症有关 谱系障碍（ASD）和双相情感障碍。我们以前发现MARK介导的磷酸化 突触支架蛋白PSD-95对于双向树突棘可塑性是重要的。而且我们 初步研究表明，前脑锥体神经元中MARK 1的缺失导致脊柱形成减少， 延迟空间学习此外，我们观察到AMPA的突触水平显著增加， MARK 1条件性KO（cKO）海马中的受体亚基GluR 2。相反，在神经元中， 用人类MARK 1替代啮齿动物MARK 1，我们观察到棘密度增加， 形态让人联想到人类神经元。这些令人兴奋的数据使我们假设MARK 1的缺失 导致过早的树突棘稳定，这限制了棘密度并损害学习。 相反，人MARK 1显示增强的激酶活性，导致树突棘幼态持续， 增加脊柱密度，这有助于人类的高认知功能。目标1将测试 假设人类MARK 1通过调节PSD支架和GluR 2来促进脊柱幼态持续 贩卖人口目的2将检验人类MARK 1活性的时空动态改变是 对脊椎幼态持续的影响。我们将利用FRET、FRAP、超分辨率成像和两个- 光子谷氨酸释放我们将用生化分析来补充这些成像方法， MARK 1活性的光遗传学操纵。完成拟议的实验将确立以下方面的作用： MARK 1在人类神经元中观察到树突棘幼态持续。结果可以揭示分子 人类大脑高级认知功能的潜在机制。

Project Summary A key cellular substrate underlying learning and memory is the plasticity of dendritic spines, which are sites of excitatory synaptic inputs in the mammalian brain. Dendritic spines show protracted synaptic maturation during human brain development, leading to longer spines with higher density in adulthood as compared with rodents. This extraordinary neoteny of spines is believed to underlie the high cognitive performance in humans. However, there remains a dearth of knowledge regarding the molecular mechanisms that contribute to dendritic spine neoteny unique to humans. One way to approach this issue is to examine genes that show adaptive evolution along the human lineage. These genes are under positive selection pressure and are likely to play a role in human speciation. In particular, genes that show adaptive evolution and genetically linked to neurodevelopmental disorders are strong candidates that may contribute to the high cognitive capacity of the human brain. To date, there are only a handful of genes reported to fit both criteria. One of the genes encodes the Microtubule Affinity Regulating Kinase 1 (MARK1), a Ser/Thr kinase highly expressed in the brain. MARK1 displays strong evidence of adaptive evolution in the lineage leading to humans, and single nucleotide polymorphisms (SNPs) of MARK1 are associated with autism spectrum disorders (ASD) and bipolar disorder. We previously found MARK-mediated phosphorylation of the synaptic scaffolding protein PSD-95 is important for bidirectional dendritic spine plasticity. Moreover, our preliminary studies show loss of MARK1 in forebrain pyramidal neurons leads to reduced spine formation and delayed spatial learning. In addition, we observed a significant increase in the synaptic levels of the AMPA receptor subunit GluR2 in the MARK1 conditional KO (cKO) hippocampus. By contrast, in neurons where rodent MARK1 was replaced with human MARK1, we observed increased spine density and immature morphology reminiscent of human neurons. These exciting data led us to hypothesize that loss of MARK1 leads to premature dendritic spine stabilization, which limits spine density and impairs learning. Conversely, human MARK1 shows enhanced kinase activity leading to dendritic spine neoteny and increased spine density, which contributes to high cognitive functions in humans. Aim 1 will test the hypothesis that human MARK1 contributes to spine neoteny through regulating the PSD scaffold and GluR2 trafficking. Aim 2 will test the hypothesis that altered spatiotemporal dynamics of human MARK1 activity is responsible for its effects on spine neoteny. We will utilize FRET, FRAP, super resolution imaging, and two- photon glutamate uncaging. We will complement these imaging approaches with biochemical analyses and optogenetic manipulation of MARK1 activity. Completion of the proposed experiments will establish a role for MARK1 in dendritic spine neoteny observed in human neurons. The results can shed light on the molecular mechanisms underlying high level cognitive functions of the human brain.