Variation in Dube3a expression affects neurotransmission at the Drosophila neuromuscular junction.
Variation in Dube3a expression affects neurotransmission at the Drosophila neuromuscular junction.
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DOI：
10.1242/bio.20148045
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发表时间：
2015-05-06
期刊：
影响因子：
2.4
通讯作者：
Reiter LT
中科院分区：
文献类型：
--
作者：
Valdez C;Scroggs R;Chassen R;Reiter LT
神经元中UBE 3A表达水平的变化可导致从安吉尔曼综合征（AS）（水平降低）到自闭症（水平升高）等神经遗传性疾病。在这里，我们研究了不同的UBE 3A水平对神经元功能的影响，使用果蝇神经肌肉接头作为这两种神经遗传性疾病的模型。相对于对照（单独C155>+），使用泛神经元GAL 4驱动C155-GAL 4（C155-GAL 4> UAS-Dube 3a），在1Hz间歇性诱发兴奋性接点电位（EJPs）的刺激在15 Hz时在显著更高比例的Dube 3a过表达者中未能诱发EJPs。然而，在没有失败的Dube 3a过表达幼虫神经元中，与对照相比，在训练开始时EJP振幅或在训练过程中EJP振幅的降低速率没有差异。在不存在河豚毒素（TTX）的情况下，与对照相比，在显著更多的C155-GAL 4> UAS-Dube 3a幼虫中观察到自发EJPs。在TTX的存在下，自发性和诱发性EJPs被完全阻断，mEJP的振幅和频率在基因型之间没有差异。这些数据表明，野生型Dube 3a的过度表达，而不是泛素化缺陷Dube 3a-C/A蛋白，损害运动神经元轴突支持紧密间隔的动作电位序列的能力，同时增加兴奋性。EJPs诱发在15 Hz的情况下Dube 3a（Dube 3a 15 b纯合子突变体幼虫）衰减更迅速，在30刺激的过程中相比，w1118控制，Dube 3a 15 b幼虫肌肉有显着更多的负静息膜电位（RMP）。然而，这些结果不能在肌肉或神经元中单独使用Dube 3a的RNAi敲低来概括，这表明更多的整体发育缺陷导致了这种表型。这些数据表明，降低UBE 3A表达水平可能会导致全局变化，影响RMP和神经肌肉接头处运动神经元的神经递质释放。UBE 3A的低表达和过表达对膜电位和突触传递的类似影响可能是在AS和自闭症中观察到的突触可塑性缺陷的基础。
Changes in UBE3A expression levels in neurons can cause neurogenetic disorders ranging from Angelman syndrome (AS) (decreased levels) to autism (increased levels). Here we investigated the effects on neuronal function of varying UBE3A levels using the Drosophila neuromuscular junction as a model for both of these neurogenetic disorders. Stimulations that evoked excitatory junction potentials (EJPs) at 1 Hz intermittently failed to evoke EJPs at 15 Hz in a significantly higher proportion of Dube3a over-expressors using the pan neuronal GAL4 driver C155-GAL4 (C155-GAL4>UAS-Dube3a) relative to controls (C155>+ alone). However, in the Dube3a over-expressing larval neurons with no failures, there was no difference in EJP amplitude at the beginning of the train, or the rate of decrease in EJP amplitude over the course of the train compared to controls. In the absence of tetrodotoxin (TTX), spontaneous EJPs were observed in significantly more C155-GAL4>UAS-Dube3a larva compared to controls. In the presence of TTX, spontaneous and evoked EJPs were completely blocked and mEJP amplitude and frequency did not differ among genotypes. These data suggest that over-expression of wild type Dube3a, but not a ubiquitination defective Dube3a-C/A protein, compromises the ability of motor neuron axons to support closely spaced trains of action potentials, while at the same time increasing excitability. EJPs evoked at 15 Hz in the absence of Dube3a (Dube3a15b homozygous mutant larvae) decayed more rapidly over the course of 30 stimulations compared to w1118 controls, and Dube3a15b larval muscles had significantly more negative resting membrane potentials (RMP). However, these results could not be recapitulated using RNAi knockdown of Dube3a in muscle or neurons alone, suggesting more global developmental defects contribute to this phenotype. These data suggest that reduced UBE3A expression levels may cause global changes that affect RMP and neurotransmitter release from motorneurons at the neuromuscular junction. Similar affects of under- and over-expression of UBE3A on membrane potential and synaptic transmission may underlie the synaptic plasticity defects observed in both AS and autism.