MARK1 in dendritic spine neoteny

项目摘要 支持学习和记忆的一个关键细胞底物是树突棘的可塑性，树突棘是 哺乳动物大脑中兴奋性突触输入的位置。树突棘显示延长的突触 在人类大脑发育过程中成熟，导致成年后脊椎更长、密度更高 与啮齿动物相比。这种非同寻常的新生脊椎被认为是高度认知的基础 在人类身上的表现。然而，关于分子方面的知识仍然很匮乏。 导致人类独有的树突状脊椎新生的机制。解决这一问题的一种方法 问题是检查沿着人类血统显示适应性进化的基因。这些基因都在 正向选择压力，并可能在人类物种形成中发挥作用。特别是，显示出 适应性进化和与神经发育障碍的基因联系是可能的有力候选者 有助于人类大脑的高认知能力。到目前为止，只有少数几个基因 据报道符合这两个标准。其中一个基因编码微管亲和力调节激酶1(Mark1)，a 丝氨酸/苏氨酸蛋白激酶在脑内高表达。Mark1显示出强烈的证据表明，在 导致人类的血统和Mark1的单核苷酸多态(SNPs)与自闭症相关 谱系障碍(ASD)和双相情感障碍。我们先前发现Mark介导的磷酸化 突触支架蛋白PSD-95对双向树突棘的可塑性起重要作用。而且，我们的 初步研究表明，前脑锥体神经元中Mark1的缺失会导致脊柱形成减少和 延迟的空间学习。此外，我们观察到AMPA的突触水平显著增加 Mark1条件性KO(CKO)海马区的受体亚单位GluR2。相比之下，在神经元中， 啮齿动物Mark1被人类Mark1取代，我们观察到脊椎密度增加和幼稚 形态使人联想到人类神经元。这些令人兴奋的数据使我们假设Mark1的丢失 导致树突状棘突过早稳定，从而限制脊椎密度并损害学习。 相反，人类Mark1表现出增强的激酶活性，导致树突状脊柱新生和 增加脊椎密度，这有助于提高人类的认知功能。目标1将测试 人类Mark1通过调节PSD支架和GluR2参与脊柱新生的假说 贩卖人口。目标2将检验这样一种假设，即人类Mark1活动的时空动力学改变是 对其对脊柱新生的影响负责。我们将使用FRET、FRAP、超分辨率成像和两个- 光子谷氨酸去化。我们将用生化分析来补充这些成像方法 MARK1活性的光基因操作。拟议实验的完成将为 树突棘中的Mark1在人类神经元中观察到的新生。这一结果可以帮助我们了解分子 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.