Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht University, 3584 CG Utrecht, The Netherlands.
Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
J Neurosci. 2018 Jan 17;38(3):613-630. doi: 10.1523/JNEUROSCI.0662-17.2017. Epub 2017 Dec 1.
During embryonic development, axons extend over long distances to establish functional connections. In contrast, axon regeneration in the adult mammalian CNS is limited in part by a reduced intrinsic capacity for axon growth. Therefore, insight into the intrinsic control of axon growth may provide new avenues for enhancing CNS regeneration. Here, we performed one of the first miRNome-wide functional miRNA screens to identify miRNAs with robust effects on axon growth. High-content screening identified miR-135a and miR-135b as potent stimulators of axon growth and cortical neuron migration and in male and female mice. Intriguingly, both of these developmental effects of miR-135s relied in part on silencing of Krüppel-like factor 4 (KLF4), a well known intrinsic inhibitor of axon growth and regeneration. These results prompted us to test the effect of miR-135s on axon regeneration after injury. Our results show that intravitreal application of miR-135s facilitates retinal ganglion cell (RGC) axon regeneration after optic nerve injury in adult mice in part by repressing KLF4. In contrast, depletion of miR-135s further reduced RGC axon regeneration. Together, these data identify a novel neuronal role for miR-135s and the miR-135-KLF4 pathway and highlight the potential of miRNAs as tools for enhancing CNS axon regeneration. Axon regeneration in the adult mammalian CNS is limited in part by a reduced intrinsic capacity for axon growth. Therefore, insight into the intrinsic control of axon growth may provide new avenues for enhancing regeneration. By performing an miRNome-wide functional screen, our studies identify miR-135s as stimulators of axon growth and neuron migration and show that intravitreal application of these miRNAs facilitates CNS axon regeneration after nerve injury in adult mice. Intriguingly, these developmental and regeneration-promoting effects rely in part on silencing of Krüppel-like factor 4 (KLF4), a well known intrinsic inhibitor of axon regeneration. Our data identify a novel neuronal role for the miR-135-KLF4 pathway and support the idea that miRNAs can be used for enhancing CNS axon regeneration.
在胚胎发育过程中，轴突延伸很长的距离以建立功能连接。相比之下，成年哺乳动物中枢神经系统中的轴突再生受到内在轴突生长能力降低的部分限制。因此，深入了解轴突生长的内在控制可能为增强中枢神经系统再生提供新途径。在这里，我们进行了第一次 miRNA 组范围内的功能 miRNA 筛选之一，以鉴定对轴突生长具有强大影响的 miRNA。高内涵筛选鉴定出 miR-135a 和 miR-135b 是雄性和雌性小鼠中轴突生长和皮质神经元迁移的有效刺激物。有趣的是，miR-135s 的这两种发育作用部分依赖于 Krüppel 样因子 4（KLF4）的沉默，KLF4 是一种已知的内在轴突生长和再生抑制剂。这些结果促使我们测试 miR-135s 对损伤后轴突再生的影响。我们的结果表明，miR-135s 的玻璃体内应用部分通过抑制 Krüppel 样因子 4（KLF4）促进成年小鼠视神经损伤后的视网膜神经节细胞（RGC）轴突再生。相比之下，miR-135s 的耗竭进一步减少了 RGC 轴突再生。总之，这些数据确定了 miR-135s 和 miR-135-KLF4 途径的新神经元作用，并强调了 miRNA 作为增强中枢神经系统轴突再生的工具的潜力。成年哺乳动物中枢神经系统中的轴突再生受到内在轴突生长能力降低的部分限制。因此，深入了解轴突生长的内在控制可能为增强再生提供新途径。通过进行 miRNA 组范围内的功能筛选，我们的研究确定 miR-135s 是轴突生长和神经元迁移的刺激物，并表明这些 miRNA 的玻璃体内应用促进了成年小鼠神经损伤后的中枢神经系统轴突再生。有趣的是，这些发育和促进再生的作用部分依赖于 Krüppel 样因子 4（KLF4）的沉默，KLF4 是一种已知的内在轴突再生抑制剂。我们的数据确定了 miR-135-KLF4 途径的新神经元作用，并支持使用 miRNA 增强中枢神经系统轴突再生的想法。
