The role of mammalian CAMTA proteins in transcriptional control of neuronal morphology and long-term memory

长期记忆的形成需要神经元长期的结构和功能适应。为了指导这些适应，突触活动启动钙依赖性信号级联反应，导致神经元基因表达的变化。这种突触到细胞核的通讯涉及钙/钙调素依赖性转录调节因子的激活，包括CREB、CBP、MeCP2和MEF2。最近发现了一个新的转录调节因子家族，即所谓的钙调素结合转录激活因子（CAMTA）蛋白。两个哺乳动物CAMTA家族成员，CAMTA1和CAMTA2，在小鼠和人类大脑中高度表达。作为钙调素依赖的转录调节因子，它们可能参与突触活动依赖的基因表达，这是记忆形成的基础。与这一观点一致，遗传学研究报告了CAMTA1基因多态性与人类认知能力之间的关联。我们最近未发表的实验表明，成年小鼠海马中shRNA介导的CAMTAs敲低会导致长期记忆性能受损。此外，我们发现CAMTA在培养的小鼠海马神经元中敲除会导致树突生长受损。树突是突触输入和信号整合的主要部位。因此，它们的形态对神经元的功能特性和认知功能有重要影响。基于我们未发表的研究结果，我们因此认为CAMTA蛋白通过神经元形态的转录控制介导长期记忆的形成。在本研究中，我们将采用小鼠海马神经元体外和小鼠海马体内功能丧失和功能获得的方法来研究哺乳动物CAMTA蛋白在树突和树突脊柱形态发生和长期记忆形成中的作用。此外，我们将使用无偏倚的基因组学和生物信息学方法来鉴定介导CAMTA形态学和认知功能丧失表型的神经元中的CAMTA靶基因。最后，我们将研究连接突触活性和CAMTA转录活性的信号机制。

The formation of long-term memories requires long-lasting structural and functional adaptations of neurons. To instruct these adaptations, synaptic activity initiates calcium-dependent signaling cascades that lead to changes in neuronal gene expression. This synapse-to-nucleus communication involves the activation of calcium/calmodulin-dependent transcriptional regulators that include CREB, CBP, MeCP2, and MEF2. Recently a novel family of transcriptional regulators, the so-called calmodulin-binding transcription activator (CAMTA) proteins, were identified. The two mammalian CAMTA family members, CAMTA1 and CAMTA2, are highly expressed in the mouse and human brain. As calmodulin-dependent transcriptional regulators, they might be involved in synaptic activity-dependent gene expression that underlies memory formation. In line with this notion, genetic studies reported an association between CAMTA1 gene polymorphisms and cognitive performance in humans. Our recent unpublished experiments revealed that shRNA mediated knock-down of CAMTAs in the hippocampus of adult mice causes impaired long-term memory performance. In addition, we found that CAMTA knock-down in cultured mouse hippocampal neurons causes impaired dendrite growth. Dendrites are the major site of synaptic input and signal integration. Their morphology thus has a major influence on the functional properties of neurons and impacts on cognitive function. Based on our unpublished findings we thus suggest that CAMTA proteins mediate the formation of long-term memories via transcriptional control of neuronal morphology. In this proposal we will use loss-of-function and gain-of-function approaches in mouse hippocampal neurons in vitro and in the mouse hippocampus in vivo to study the role of mammalian CAMTA proteins in dendrite and dendritic spine morphogenesis and in the formation of long-term memories. In addition, we will use unbiased genomic and bioinformatics approaches to identify CAMTA target genes in neurons that mediate the morphological and cognitive CAMTA loss-of-function phenotypes. Finally, we will investigate the signaling mechanisms that link synaptic activity to CAMTA transcriptional activity.