Abstract：
The presynapse performs an essential role in brain communication via the activity-dependent release of neurotransmitters. However, the sequence of events through which a presynapse acquires functionality is relatively poorly understood, which is surprising, since mutations in genes essential for its operation are heavily implicated in neurodevelopmental disorders. We addressed this gap in knowledge by determining the developmental trajectory of synaptic vesicle (SV) recycling pathways in primary cultures of rat hippocampal neurons. Exploiting a series of optical and morphological assays, we revealed that the majority of nerve terminals displayed activity-dependent calcium influx from 3 days in vitro (DIV), immediately followed by functional evoked exocytosis and endocytosis, although the number of responsive nerve terminals continued to increase until the second week in vitro. However, the most intriguing discovery was that activity-dependent bulk endocytosis (ADBE) was only observed from DIV 14 onwards. Importantly, optimal ADBE recruitment was delayed until DIV 21 in Fmr1 knockout neurons, which model Fragile X Syndrome (FXS). This implicates the delayed recruitment of ADBE as a potential contributing factor in the development of circuit dysfunction in FXS, and potentially other neurodevelopmental disorders.
摘要：
突触前通过神经递质的活动依赖性释放在大脑交流中发挥重要作用。然而,预先同步获取功能的事件序列相对知之甚少，令人惊讶的是，因为对其运作至关重要的基因突变与神经发育障碍密切相关。我们通过确定大鼠海马神经元原代培养物中突触小泡（SV）再循环途径的发育轨迹，解决了这一知识差距。利用一系列光学和形态学检测，我们发现，大多数神经末梢显示活性依赖性钙流入从3天体外（DIV），紧接着是功能性诱发的胞吐作用和内吞作用，尽管反应性神经末梢的数量持续增加直到体外第二周。然而,最有趣的发现是,仅从DIV14开始观察到活性依赖性本体内吞作用(ADBE).重要的是,最佳ADBE募集延迟到Fmr1敲除神经元的DIV21，该模型是脆性X综合征(FXS)的模型。这暗示ADBE的延迟募集是FXS中电路功能障碍发展的潜在促成因素，以及潜在的其他神经发育障碍。
