M1 circuit dysfunction in MECP2 duplication syndrome

 描述（由申请人提供）：自闭症相关的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。这种不平衡可能导致自闭症谱系障碍（ASD）中出现的僵化、受限的行为库、对同一性的坚持，以及有时像学者一样的行为。运动功能障碍是ASD常见的早期症状。运动学习以及形成新行为的能力对于ASD儿童来说是必不可少的，以便进行社会联系和交流。这些儿童通常有非常有限的运动曲目，需要强化治疗，以改善和学习新的运动技能。甲基-CpG结合蛋白2（MeCP 2）是一种转录调节因子，其促进了 通过基因表达和剪接的活性依赖性调节来维持神经回路的稳态。它的复制导致MECP 2-复制综合征，这是自闭症的100%渗透性单基因原因，导致男性进行性智力残疾、自闭症、运动功能障碍、痉挛和癫痫。经工程改造以两倍于正常水平过表达MeCP 2的小鼠表现出类似的神经学表型。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（柯林斯等人，2004），其随着时间的推移发展为运动功能障碍、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是共有的，并且使用旋转棒训练作为巩固重复运动行为的范例进行研究（柯林斯等人，2004; Kwon等人，2006; Nakatani等人，2009; Rothwell等人，2014年）。在这里，我们专注于初级运动皮层（M1区），这是已知的有助于运动学习。我们将使用慢性，在体内，2-光子成像与敏感的慢性钙指示剂GCaMP 6s遵循动态模式的神经元活动引起的运动过程中在M1区。研究将从症状前阶段开始，将包括一段运动技能（旋转棒）学习期，其中突变动物的表现优于同窝对照动物，并将终止于运动消退期。在耳技能学习期间，将遵循相对于运动速度、不同细胞类型之间的成对同步性（“功能连接性”）和放电可靠性的调谐曲线，并与表现和运动技能获取记忆相关。将对在锥体神经元中相对于抑制性中间神经元中选择性表达MECP 2复制的小鼠进行行为表征和研究。具体目标1：研究MECP 2重复（Tg 1）小鼠M1区回路在症状前阶段的运动学习过程中如何变化。具体目标2：跟踪MECP 2-重复Tg 1区M1回路功能如何从症状前阶段变化到症状后阶段。我们的目的是建立一个链接的模式M1电路功能障碍和异常的运动行为在这个模型的MECP 2重复综合征。

 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.