School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland; Department of Cognitive, Linguistic and Psychological Sciences, Brown University, Providence, RI 02912, USA.
Neurosci Lett. 2013 Oct 25;555:36-41. doi: 10.1016/j.neulet.2013.09.007. Epub 2013 Sep 11.
Tetanus toxin light chain has been used for some time as a genetically-encoded tool to inhibit neurotransmission and thereby dissect mechanisms underlying neural circuit formation and function. In addition to cleaving v-SNARE proteins involved in axonal neurotransmitter release, tetanus toxin light chain can also block activity-dependent dendritic exocytosis. The application of tetanus toxin light chain as a research tool in mammalian models, however, has been limited to a small number of cell types. Here we have induced expression of tetanus toxin light chain in a very small number of fluorescently labeled neurons in many regions of the adult mouse brain. This was achieved by crossing SLICK (single-neuron labeling with inducible cre-mediated knockout) transgenic lines with RC::Ptox mice that have Cre recombinase-controlled expression of the tetanus toxin light chain. Using this system we have examined the cell-autonomous effects of tetanus toxin light chain expression on dendritic spines in vivo. We find that dendritic spine density is reduced by 15% in tetanus toxin expressing hippocampal CA1 pyramidal cells, while spine morphology is unaltered. This effect is likely to be a consequence of inhibition of activity-dependent dendritic exocytosis and suggests that on-going plasticity-associated exocytosis is required for long-term dendritic spine maintenance in vivo.
破伤风毒素轻链在一段时间内一直被用作一种遗传编码工具，以抑制神经递质传递，从而剖析神经回路形成和功能的机制。除了切割参与轴突神经递质释放的 v-SNARE 蛋白外，破伤风毒素轻链还可以阻断活性依赖性树突小泡胞吐。然而，破伤风毒素轻链作为一种研究工具在哺乳动物模型中的应用仅限于少数几种细胞类型。在这里，我们通过将 SLICK（通过诱导型 Cre 介导的敲除进行单神经元标记）转基因系与 RC::Ptox 小鼠杂交，在成年小鼠大脑的许多区域中诱导表达了非常少量荧光标记神经元的破伤风毒素轻链。RC::Ptox 小鼠的破伤风毒素轻链表达受 Cre 重组酶的控制。使用该系统，我们研究了破伤风毒素轻链表达对体内树突棘的细胞自主效应。我们发现，破伤风毒素表达的海马 CA1 锥体神经元中的树突棘密度降低了 15%，而棘突形态未改变。这种效应可能是由于活性依赖性树突小泡胞吐抑制的结果，表明体内长期维持树突棘需要与可塑性相关的胞吐作用。
