驱动蛋白适配子Calsyntenin1失调影响脆性X综合征小鼠运动技能学习的小脑环路机制

运动学习能力下降常见于脆性X综合征（FXS）和孤独谱系障碍（ASD），严重限制了患者融入社会的能力，小脑外侧部发育障碍可能与其有关，但具体病理机制并不清楚。申请人前期发现驱动蛋白适配子Calsyntenin 1（CLSTN1）是FMRP的靶分子，CLSTN1在FXS动物模型Fmr1KO小鼠小脑表达失调。前人已证明CLSTN1在突触发育和轴突生长导向中有重要作用，我们推测CLSTN1表达失调可能损害输入到小脑浦肯野细胞（PC）的关键投射通路的结构和功能，影响运动技能学习。本项目通过训练Fmr1基因敲除小鼠、小脑CLSTN1敲除和过表达等小鼠模型完成单个食丸抓取任务，结合在体光纤记录PC钙活动，脑片全细胞膜片钳记录攀缘纤维和平行纤维激活诱导的PC电活动，在体双光子成像观察PC单个突触形成、维持和消失变化。证明FXS小脑CLSTN1表达失调引起神经环路结构和功能变化是其运动技能学习障碍的关键原因

Motor skills learning ability deficits are notable in Fragile X syndrome and other autism spectrum disorders，which affect their motor learning and social performance. The development delay of lateral cerebellum may be the pathological basis, but the specific neurophysiological processes underlying the development delay of cerebellum remains poorly understood. Calsyntenin 1 (CLSTN1) form a linker protein between distinct populations of vesicles and kinesin motors for axonal transport，and is implicated in synapse formation and synaptic plasticity by findings in worms, mice and humans. CLSTN1-deficiency phenotypes range from synapse numbers to synaptic Ca2+-dynamics. We have previously demonstrated that Fmr1 KO mice, fragile X syndrome (FXS), have decreased CLSTN1 expression and social behavioral impairments. Overexpression of CLSTN1 in dentate gyrus of hippocampus of Fmr1 KO mice can repair hippocampus-dependent memory deficit. We hypothesize the CLSTN1 influences cerebellar circuit development and adult behavior via regulation of excitation-inhibition balance. In this study, using single-seed grabing during motor-skill learning, electrophysiological studies, and in vivo two photon imaging, to uncover the circuit-level alterations in the Fmr1-/- mouse model that underlie atypical motor skill learning associated with FXS，and to dissect out mechanisms by which the CLSTN1 could be affecting the synaptic development and circuit structure at the cerebellum. Our study will illustrate a novel neuromodulatory role of CLSTN1-mediated signaling in regulating the cerebellar circuit development and motor skill learning behavior.