The microtubule cytoskeleton is a major driving force of neuronal circuit development. Fine-tuned remodelling of this network by selective activation of microtubule-regulating proteins, including microtubule-severing enzymes, has emerged as a central process in neuronal wiring. Tubulin posttranslational modifications control both microtubule properties and the activities of their interacting proteins. However, whether and how tubulin posttranslational modifications may contribute to neuronal connectivity has not yet been addressed. Here we show that the microtubule-severing proteins p60-katanin and spastin play specific roles in axon guidance during zebrafish embryogenesis and identify a key role for tubulin polyglutamylation in their functional specificity. Furthermore, our work reveals that polyglutamylases with undistinguishable activities in vitro, TTLL6 and TTLL11, play exclusive roles in motor circuit wiring by selectively tuning p60-katanin- and spastin-driven motor axon guidance. We confirm the selectivity of TTLL11 towards spastin regulation in mouse cortical neurons and establish its relevance in preventing axonal degeneration triggered by spastin haploinsufficiency. Our work thus provides mechanistic insight into the control of microtubule-driven neuronal development and homeostasis and opens new avenues for developing therapeutic strategies in spastin-associated hereditary spastic paraplegia.

中文翻译：

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微管蛋白谷氨酰化通过选择性调节微管切断酶来调节轴突导向。


微管细胞骨架是神经元回路发育的主要驱动力。通过选择性激活微管调节蛋白（包括微管切断酶）来微调该网络的重塑已成为神经元布线的核心过程。微管蛋白翻译后修饰控制微管特性及其相互作用蛋白的活性。然而，微管蛋白翻译后修饰是否以及如何促进神经元连接尚未得到解决。在这里，我们表明微管切断蛋白 p60-katanin 和 spastin 在斑马鱼胚胎发生过程中的轴突导向中起特定作用，并确定了微管蛋白多谷氨酰化在其功能特异性中的关键作用。此外，我们的工作揭示了在体外具有难以区分活性的聚谷氨酰酶 TTLL6 和 TTLL11，通过选择性调整 p60-katanin 和 spastin 驱动的电机轴突导向，在电机电路布线中发挥独家作用。我们证实了 TTLL11 对小鼠皮层神经元中 spastin 调节的选择性，并确定了其在防止 spastin 单倍体不足引发的轴突变性的相关性。因此，我们的工作为控制微管驱动的神经元发育和稳态提供了机制见解，并为开发 spastin 相关遗传性痉挛性截瘫的治疗策略开辟了新的途径。