Department of Biological Sciences, Rutgers University, Newark, New Jersey 07102.
Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel.
J Neurosci. 2020 Jul 8;40(28):5413-5430. doi: 10.1523/JNEUROSCI.2730-19.2020. Epub 2020 Jun 4.
Diverse neuronal populations with distinct cellular morphologies coordinate the complex function of the nervous system. Establishment of distinct neuronal morphologies critically depends on signaling pathways that control axonal and dendritic development. The Sema3A-Nrp1/PlxnA4 signaling pathway promotes cortical neuron basal dendrite arborization but also repels axons. However, the downstream signaling components underlying these disparate functions of Sema3A signaling are unclear. Using the novel knock-in male and female mice, generated by CRISPR/cas9, we show here that the KRK motif in the PlxnA4 cytoplasmic domain is required for Sema3A-mediated cortical neuron dendritic elaboration but is dispensable for inhibitory axon guidance. The RhoGEF FARP2, which binds to the KRK motif, shows identical functional specificity as the KRK motif in the PlxnA4 receptor. We find that Sema3A activates the small GTPase Rac1, and that Rac1 activity is required for dendrite elaboration but not axon growth cone collapse. This work identifies a novel Sema3A-Nrp1/PlxnA4/FARP2/Rac1 signaling pathway that specifically controls dendritic morphogenesis but is dispensable for repulsive guidance events. Overall, our results demonstrate that the divergent signaling output from multifunctional receptor complexes critically depends on distinct signaling motifs, highlighting the modular nature of guidance cue receptors and its potential to regulate diverse cellular responses. The proper formation of axonal and dendritic morphologies is crucial for the precise wiring of the nervous system that ultimately leads to the generation of complex functions in an organism. The Semaphorin3A-Neuropilin1/Plexin-A4 signaling pathway has been shown to have multiple key roles in neurodevelopment, from axon repulsion to dendrite elaboration. This study demonstrates that three specific amino acids, the KRK motif within the Plexin-A4 receptor cytoplasmic domain, are required to coordinate the downstream signaling molecules to promote Sema3A-mediated cortical neuron dendritic elaboration, but not inhibitory axon guidance. Our results unravel a novel Semaphorin3A-Plexin-A4 downstream signaling pathway and shed light on how the disparate functions of axon guidance and dendritic morphogenesis are accomplished by the same extracellular ligand .
具有不同细胞形态的多种神经元群体协调神经系统的复杂功能。不同神经元形态的建立严重依赖于控制轴突和树突发育的信号通路。Sema3A-Nrp1/PlxnA4 信号通路促进皮质神经元基底树突分支，但也排斥轴突。然而，Sema3A 信号的这些不同功能的下游信号成分尚不清楚。使用新型 CRISPR/cas9 生成的雄性和雌性 knock-in 小鼠，我们在这里表明，PlxnA4 细胞质结构域中的 KRK 基序对于 Sema3A 介导的皮质神经元树突延伸是必需的，但对于抑制性轴突导向是可有可无的。与 KRK 基序结合的 RhoGEF FARP2 在功能上与 PlxnA4 受体中的 KRK 基序具有相同的特异性。我们发现 Sema3A 激活小 GTPase Rac1，并且 Rac1 活性对于树突延伸是必需的，但对于轴突生长锥塌陷是可有可无的。这项工作确定了一种新的 Sema3A-Nrp1/PlxnA4/FARP2/Rac1 信号通路，该信号通路专门控制树突形态发生，但对于排斥性导向事件是可有可无的。总的来说，我们的结果表明，多功能受体复合物的发散信号输出取决于不同的信号基序，突出了导向信号受体的模块化性质及其调节多种细胞反应的潜力。轴突和树突形态的正确形成对于神经系统的精确布线至关重要，最终导致生物体产生复杂的功能。Semaphorin3A-Neuropilin1/Plexin-A4 信号通路已被证明在神经发育过程中具有多种关键作用，从轴突排斥到树突延伸。这项研究表明，三个特定的氨基酸，即 Plexin-A4 受体细胞质结构域中的 KRK 基序，是协调下游信号分子以促进 Sema3A 介导的皮质神经元树突延伸所必需的，但不是抑制性轴突导向。我们的结果揭示了一种新的 Semaphorin3A-Plexin-A4 下游信号通路，并阐明了同一细胞外配体如何完成轴突导向和树突形态发生的不同功能。
