Department of Neuroscience, Washington University School of Medicine, St. Louis, MO, 63110, USA.
Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, 305-8575, Japan.
Nat Commun. 2017 Nov 2;8(1):1271. doi: 10.1038/s41467-017-01333-6.
Although ubiquitin ligases have been implicated in autism, their roles and mechanisms in brain development remain incompletely understood. Here, we report that in vivo knockdown or conditional knockout of the autism-linked ubiquitin ligase RNF8 or associated ubiquitin-conjugating enzyme UBC13 in rodent cerebellar granule neurons robustly increases the number of parallel fiber presynaptic boutons and functional parallel fiber/Purkinje cell synapses. In contrast to the role of nuclear RNF8 in proliferating cells, RNF8 operates in the cytoplasm in neurons to suppress synapse differentiation in vivo. Proteomics analyses reveal that neuronal RNF8 interacts with the HECT domain protein HERC2 and scaffold protein NEURL4, and knockdown of HERC2 or NEURL4 phenocopies the inhibition of RNF8/UBC13 signaling on synapse differentiation. In behavior analyses, granule neuron-specific knockout of RNF8 or UBC13 impairs cerebellar-dependent learning. Our study defines RNF8 and UBC13 as components of a novel cytoplasmic ubiquitin-signaling network that suppresses synapse formation in the brain.
尽管泛素连接酶与自闭症有关，但它们在大脑发育中的作用和机制仍不完全清楚。在这里，我们报告说，在体内敲低或条件敲除自闭症相关泛素连接酶 RNF8 或相关泛素连接酶 UBC13 在啮齿动物小脑颗粒神经元中，强烈增加了平行纤维突触前末梢和功能性平行纤维/浦肯野细胞突触的数量。与核 RNF8 在增殖细胞中的作用相反，RNF8 在神经元中在细胞质中起作用，以抑制体内突触分化。蛋白质组学分析表明，神经元 RNF8 与 HECT 结构域蛋白 HERC2 和支架蛋白 NEURL4 相互作用，敲低 HERC2 或 NEURL4 可模拟 RNF8/UBC13 信号对突触分化的抑制作用。在行为分析中，颗粒神经元特异性敲除 RNF8 或 UBC13 会损害小脑依赖的学习。我们的研究将 RNF8 和 UBC13 定义为一种新型细胞质泛素信号网络的组成部分，该网络抑制大脑中的突触形成。
