M1 circuit dysfunction in MECP2 duplication syndrome

 描述(申请人提供)：自闭症相关基因突变通过扰乱大脑中突触连接的稳定性和可塑性之间的平衡来改变学习能力。这种不平衡可能会导致自闭症谱系障碍(ASD)中出现的僵化、受限的行为模式，坚持相同，有时还会出现学者样的行为。运动功能障碍是ASD常见的早期症状。运动学习和形成新的行为体系的能力对于患有自闭症的儿童来说是必要的，以便进行社交联系和交流。这些儿童的动作能力往往非常有限，需要强化治疗，以提高和学习新的运动技能。甲基CpG结合蛋白2(MeCP2)是一种转录调节因子，参与 通过依赖活性的基因表达和剪接调节维持神经回路的动态平衡。它的复制导致MECP2重复综合征，这是自闭症的100%穿透性单基因原因，导致男性进行性智力残疾、自闭症、运动障碍、痉挛和癫痫。基因工程使MeCP2在两倍正常水平过表达的小鼠表现出类似的神经表型。值得注意的是，在出生后发育的早期，这些动物表现出增强的运动学习和记忆(Collins等人，2004年)，随着时间的推移，这会进展为运动功能障碍、痉挛和癫痫。这种增强的运动学习表型在几种自闭症模型中都是相同的，并使用旋转臂训练作为巩固重复运动行为的范式进行研究(Collins等人，2004；Kwan等人，2006；Nakatani等人，2009；Rothwell等人，2014)。在这里，我们关注初级运动皮质(M1区)，这是已知的有助于运动学习的区域。我们将使用慢性、活体、双光子成像和敏感的慢性钙指示剂GCaMP6来跟踪M1区运动过程中诱发的神经元活动的动态模式。这项研究将在症状前阶段开始，将包括一段运动技能(旋转)学习阶段，在这段时间内，突变动物的表现好于同年龄的对照动物，并将终止于运动退化阶段。在运动技能学习过程中，将遵循与运动速度、不同细胞类型之间的成对同步(“功能连接”)和发射的可靠性相关的调谐曲线，并将其与表现和运动技能习得记忆相关联。在锥体神经元和抑制性中间神经元中选择性表达MECP2复制的小鼠将被描述和研究。具体目标1：研究MECP2重复(Tg1)小鼠区域M1回路在症状前期运动学习过程中的变化。具体目标2：观察MECP2-复制Tg1区M1区电路功能从症状前到症状后的变化。我们的目标是在MECP2复制综合征的这个模型中建立M1回路功能障碍的模式和异常运动行为之间的联系。

 DESCRIPTION (provided by applicant): Autism-associated genetic mutations produce altered learning abilities by perturbing the balance between stability and plasticity of synaptic connections in the brain. Such an imbalance may contribute to the rigid, restricted behavioral repertoire, insistence on sameness, and at times savant-like behavior seen in autism spectrum disorders (ASD). Motor dysfunction is a common and early symptom of ASD. Motor learning and with it the ability to form a new behavioral repertoire is essential for children with ASD in order to socially connect and communicate. These children often have a very restricted movement repertoire and require intensive therapy in order to improve and learn new motor skills. Methyl-CpG-binding protein 2 (MeCP2) is a transcriptional regulator that contributes to the maintenance of neural circuit homeostasis through the activity-dependent modulation of gene expression and splicing. Its duplication causes MECP2-duplication syndrome, an 100% penetrant monogenic cause of autism, which leads to progressive intellectual disability, autism, motor dysfunction, spasticity, and epilepsy in males. Mice engineered to overexpress MeCP2 at twice normal levels exhibit a similar neurological phenotype. Remarkably, early in postnatal development these animals exhibit enhanced motor learning and memory (Collins et al., 2004), which over time progresses to motor dysfunction, spasticity and epilepsy. Such enhanced motor learning phenotype is shared across several models of autism, and is studied using rotarod training as a paradigm for consolidation of repetitive motor behaviors (Collins et al., 2004; Kwon et al., 2006; Nakatani et al., 2009; Rothwell et al., 2014). Here, we focus on primary motor cortex (area M1), which is known to contribute to motor learning. We will use chronic, in vivo, 2-photon imaging with the sensitive chronic calcium indicator GCaMP6s to follow dynamic patterns of neuronal activity elicited during locomotion in area M1. The study will start at the pr- symptomatic stage, will include a period of motor skill (rotarod) learning in which mutant animals perform better than littermate controls, and will terminate into the time period of motor regression. Tuning curves relative to the speed of locomotion, pairwise synchrony between different cell types ("functional connectivity") and reliability of firing will be followed during otor skill learning and correlated with performance and motor skill acquisition memory. Mice with selective expression of the MECP2 duplication in pyramidal neurons versus inhibitory interneurons will be characterized behaviorally and studied. Specific aim 1: Study how MECP2-duplication (Tg1) mouse area M1 circuits change during motor learning at the pre-symptomatic stage. Specific aim 2: Follow how MECP2-duplication Tg1 area M1 circuit function changes from the pre-symptomatic to the post-symptomatic stage. We aim to forge a link between patterns of M1 circuit dysfunction and abnormal motor behavior in this model of the MECP2 duplication syndrome.