Division of Biomedical Sciences, University of California, Riverside, Riverside, CA 92521, USA.
Graduate Program in Cell, Molecular and Developmental Biology, University of California, Riverside, Riverside, CA 92521, USA.
Neuron. 2019 Feb 20;101(4):690-706.e10. doi: 10.1016/j.neuron.2019.01.022. Epub 2019 Feb 4.
How a neuron acquires an axon is a fundamental question. Piecemeal identification of many axonogenesis-related genes has been done, but coordinated regulation is unknown. Through unbiased transcriptome profiling of immature primary cortical neurons during early axon formation, we discovered an association between axonogenesis and neuron-specific alternative splicing. Known axonogenesis genes exhibit little expression alternation but widespread splicing changes. Axonogenesis-associated splicing is governed by RNA binding protein PTBP2, which is enriched in neurons and peaks around axonogenesis in the brain. Cortical depletion of PTBP2 prematurely induces axonogenesis-associated splicing, causes imbalanced expression of axonogenesis-associated isoforms, and specifically affects axon formation in vitro and in vivo. PTBP2-controlled axonogenesis-associated Shtn1 splicing determines SHTN1's capacity to regulate actin interaction, polymerization, and axon growth. Precocious Shtn1 isoform switch contributes to disorganized axon formation of Ptbp2 neurons. We conclude that PTBP2-orchestrated alternative splicing programming is required for robust generation of a single axon in mammals.
神经元如何获得轴突是一个基本问题。虽然已经对许多与轴突发生相关的基因进行了零碎的鉴定，但协调调控尚不清楚。通过对早期轴突形成过程中未成熟的初级皮质神经元进行无偏倚的转录组谱分析，我们发现轴突发生与神经元特异性选择性剪接之间存在关联。已知的轴突发生基因表达变化不大，但广泛存在剪接变化。轴突发生相关剪接受 RNA 结合蛋白 PTBP2 调控，该蛋白在神经元中富集，在大脑中的轴突发生时达到峰值。皮质中 PTBP2 的耗竭会过早地诱导轴突发生相关剪接，导致轴突发生相关异构体的表达失衡，并特别影响体外和体内的轴突形成。PTBP2 控制的轴突发生相关 Shtn1 剪接决定了 SHTN1 调节肌动蛋白相互作用、聚合和轴突生长的能力。过早的 Shtn1 异构体转换有助于 Ptbp2 神经元中轴突形成的紊乱。我们的结论是，PTBP2 协调的选择性剪接编程是哺乳动物中生成单个轴突所必需的。
