Function of stimulus-induced MeCP2 phosphorylation

刺激诱导的MeCP2磷酸化的功能 摘要 MeCP2是识别甲基化DNA和解释编码在DNA中的表观遗传信息的关键参与者。 不同的DNA甲基化模式X连锁人MECP 2序列或拷贝数的改变 基因导致Rett综合征（RTT）或MECP2复制综合征。除了RTT引起的 突变，许多功能意义未知的错义突变已在MECP 2中被鉴定出来。 人类的基因其中两个突变位于或接近丝氨酸80或丝氨酸421，其磷酸化 状态对于调节MeCP2功能是重要的。为了充分理解MECP2在以下方面的重要作用， 由于MeCP 2在调节神经系统的发育和功能方面发挥着重要作用，因此研究MeCP 2的各个方面非常重要。 功能我们以前已经证明，丝氨酸421（S421）的磷酸化可以被诱导， S421磷酸化在调节MeCP2与基因结合中起着关键作用 启动子，神经元基因转录，兴奋性突触发生，两种类型的突触可塑性（长期 增强和突触缩放）、运动、学习和记忆。最近，我们发现S421 在分离自海马的成体神经祖细胞（aNPC）中也被磷酸化。有趣的是 刺激，S421磷酸化在aNPC中的调节和功能与那些刺激完全不同。 有丝分裂后的神经元。在aNPC中，MeCP2 S421磷酸化由生长因子诱导，与细胞生长因子相关。 细胞周期，直接由极光激酶B调节，并在调节细胞增殖和 通过Notch信号传导途径促进aNPC的分化。这些新发现进一步推广了MeCP2 磷酸化作为细胞功能中的常见调节模块。更有趣的是， 丝氨酸80（S80）似乎在有丝分裂后神经元中与S421处的磷酸化不同地调节， 并在有丝分裂后神经元和aNPC中对S421磷酸化起相反的功能作用。 总的来说，这些研究提高了MeCP2上多个位点的动态磷酸化状态的可能性。 可以形成组合密码，呈现除DNA外的另一个表观遗传调控模块 甲基化和组蛋白编码。为了验证这一假设，我们提出了几个新的Mecp2敲入， 携带点突变组合的等位基因，所述点突变消除或模拟S80和S421处的磷酸化， 并在神经发生的成熟范例中研究每个组合代码的功能输出， 小鼠和人类模型。我们的具体目标是：1）研究S80双突变的影响， S421对小鼠aNPC增殖和分化的影响 S80和S421突变对人干细胞模型中NPC增殖和分化的影响，以及3） 定义连接MeCP2磷酸化与其功能输出的分子机制。研究 MeCP2的翻译后修饰为理解MeCP2的基本功能提供了一个关键的角度。 MeCP2，这将扩大我们对MeCP2的了解，超越RTT和MECP2复制综合征。

Function of stimulus-induced MeCP2 phosphorylation Abstract MeCP2 is a key player in recognizing methylated DNA and interpreting the epigenetic information encoded in different DNA methylation patterns. Alterations in sequence or copy number of the X-linked human MECP2 gene cause either Rett syndrome (RTT) or MECP2 duplication syndrome. In addition to RTT-causing mutations, many missense mutations with unknown functional significance have been identified in the MECP2 gene in humans. Two of those mutations are at or close to serine 80 or serine 421, whose phosphorylation status is important for regulating MeCP2 function. To fully understand the significant role of MECP2 in regulating the development and function of the nervous system, it is important to study all aspects of MeCP2 function. We have previously demonstrated that phosphorylation at serine 421 (S421) can be induced by spatial learning, and that S421 phosphorylation plays critical roles in regulating MeCP2 binding to gene promoters, neuronal gene transcription, excitatory synaptogenesis, two types of synaptic plasticity (long-term potentiation and synaptic scaling), locomotion, learning and memory. Most recently, we discovered that S421 is also phosphorylated in adult neural progenitor cells (aNPC) isolated from the hippocampus. Interestingly, the stimulus, the regulation and the function of S421 phosphorylation in aNPCs are completely different from those in post-mitotic neurons. In aNPCs, MeCP2 S421 phosphorylation is induced by growth factors, linked to cell cycle, directly regulated by aurora kinase B, and plays critical roles in regulating the proliferation and differentiation of aNPCs through the Notch signaling pathway. These new findings further generalize MeCP2 phosphorylation as a common regulatory module in cellular functions. More interestingly, phosphorylation at serine 80 (S80) appears to be regulated differentially from phosphorylation at S421 in post-mitotic neurons, and plays opposing functional roles against S421 phosphorylation in both post-mitotic neurons and aNPCs. Collectively, these studies raise the possibility that dynamic phosphorylation states at multiple sites on MeCP2 may form a combinatorial code, presenting another epigenetic regulatory module in addition to DNA methylation and histone codes. To test this hypothesis, we propose to generate several novel Mecp2 knockin alleles carrying combinations of point mutations that either abolish or mimic phosphorylation at S80 and S421, and study the functional output of each combinatorial code in the well-established paradigm of neurogenesis in both mouse and human models. Our specific aims are: 1) To study the effects of double mutations at S80 and S421 on aNPC proliferation and differentiation in mouse models, 2) To study the effects of single and double mutations at S80 and S421 on NPC proliferation and differentiation in human stem cell models, and 3) To define the molecular mechanism linking MeCP2 phosphorylation with its functional output. Studying posttranslational modification of MeCP2 provides a critical angle of understanding the basic function of MeCP2, which will expand our knowledge of MeCP2 beyond RTT and MECP2 duplication syndrome.