Gene dosage-dependent transmitter release changes at neuromuscular synapses of Cacna1a R192Q knockin mice are non-progressive and do not lead to morphological changes or muscle weakness
Gene dosage-dependent transmitter release changes at neuromuscular synapses of Cacna1a R192Q knockin mice are non-progressive and do not lead to morphological changes or muscle weakness
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DOI：
10.1016/j.neuroscience.2005.04.069
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发表时间：
2005-01-01
期刊：
影响因子：
3.3
通讯作者：
Plomp, JJ
中科院分区：
文献类型：
--
作者：
Kaja, S;Van de Ven, RCG;Plomp, JJ
Ca(v)2.1通道介导神经肌肉接点（NMJ）和许多中枢突触的神经递质释放。编码基因CACNA1A的突变可能会影响神经递质释放。此前，我们培养了携带R192Q突变的小鼠，该突变与人类家族性偏瘫偏头痛1型相关，并首次显示突触前Ca2+内流增强的证据[Neuron 41(2004) 701]。在这里，我们详细描述了小鼠R192Q NMJs的递质释放，包括可能的基因剂量依赖性，随年龄变化的进展，以及相关的形态学损伤和肌肉无力。我们发现，在低Ca2+下，诱发乙酰胆碱释放的成对脉冲促进降低，释放概率升高，易释放的递质囊泡池大小增加。自发释放在Ca2+浓度范围（0.2- 5mm）内增加。在高频率的神经刺激下，我们观察到一些额外的递质释放减少。然而，通过肌电图、握力测试和肌肉收缩实验评估，没有发现传递阻滞或肌肉无力的临床证据。我们研究了成年（类似于3-6个月大）和老年（类似于21-26个月大）R192Q敲入小鼠，以评估突触前Ca2+内流慢性升高的影响，但未发现额外或进行性改变。两组小鼠NMJ大小及相关超微结构参数均未见变化。我们的研究结果加强了通过r192q突变的突触前Ca(v)2.1通道增加Ca2+通量的假设，并表明由此产生的神经递质释放改变与NMJ或肌肉无力的形态学改变无关，甚至与长期的形态学改变无关。(c) 2005 IBRO。Elsevier Ltd.出版。版权所有。
Ca(v)2.1 channels mediate neurotransmitter release at the neuromuscular junction (NMJ) and at many central synapses. Mutations in the encoding gene, CACNA1A, are thus likely to affect neurotransmitter release. Previously, we generated mice carrying the R192Q mutation, associated with human familial hemiplegic migraine type-1, and showed first evidence of enhanced presynaptic Ca2+ influx [Neuron 41 (2004) 701]. Here, we characterize transmitter release in detail at mouse R192Q NMJs, including possible gene-dosage dependency, progression of changes with age, and associated morphological damage and muscle weakness. We found, at low Ca2+, decreased paired-pulse facilitation of evoked acetylcholine release, elevated release probability, and increased size of the readily releasable transmitter vesicle pool. Spontaneous release was increased over a broad range of Ca2+ concentrations (0.2-5 mM). Upon high-rate nerve stimulation we observed some extra rundown of transmitter release. However, no clinical evidence of transmission block or muscle weakness was found, assessed with electromyography, grip-strength testing and muscle contraction experiments. We studied both adult (similar to 3-6 months-old) and aged (similar to 21-26 months-old) R192Q knockin mice to assess effects of chronic elevation of presynaptic Ca2+ influx, but found no additional or progressive alterations. No changes in NMJ size or relevant ultrastructural parameters were found, at either age. Our characterizations strengthen the hypothesis of increased Ca2+ flux through R192Q-mutated presynaptic Ca(v)2.1 channels and show that the resulting altered neurotransmitter release is not associated with morphological changes at the NMJ or muscle weakness, not even in the longer term. (c) 2005 IBRO. Published by Elsevier Ltd. All rights reserved.