The orphan receptor, G protein-coupled receptor 137 (GPR137), is an integral membrane protein involved in several types of cancer. GPR137 is expressed ubiquitously, including in the central nervous system (CNS). We established a GPR137 knockout (KO) neuro2A cell line to analyze GPR137 function in neuronal cells. KO cells were generated by genome editing using clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 and cultured as single cells by limited dilution. Rescue cells were then constructed to re-express GPR137 in GPR137 KO neuro2A cells using an expression vector with an EF1-alpha promoter. GPR137 KO cells increased cellular proliferation and decreased neurite outgrowth (i.e., a lower level of neuronal differentiation). Furthermore, GPR137 KO cells exhibited increased expression of a cell cycle regulator, cyclin D1, and decreased expression of a neuronal differentiation marker, NeuroD1. Additionally, GPR137 KO cells exhibited lower expression levels of the neurite outgrowth markers STAT3 and GAP43. These phenotypes were all abrogated in the rescue cells. In conclusion, GPR137 deletion increased cellular proliferation and decreased neuronal differentiation, suggesting that GPR137 promotes cell cycle exit and neuronal differentiation in neuro2A cells. Regulation of neuronal differentiation by GPR137 could be vital to constructing neuronal structure during brain development.

Graphical Abstract

中文翻译：

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GPR137 抑制 Neuro2a 细胞的细胞增殖并促进神经元分化

孤儿受体 G 蛋白偶联受体 137 (GPR137)是一种整合膜蛋白，与多种类型的癌症有关。GPR137广泛表达，包括中枢神经系统 (CNS)。我们建立了GPR137敲除（KO）neuro2A 细胞系来分析GPR137在神经元细胞中的功能。KO 细胞是通过使用成簇规则间隔的短回文重复序列 (CRISPR)/Cas9 进行基因组编辑而产生的，并通过有限稀释作为单细胞进行培养。然后构建救援细胞，使用带有 EF1-α 启动子的表达载体在GPR137 KO 神经2A 细胞中重新表达GPR137 。GPR137 KO 细胞增加细胞增殖并减少神经突生长（即神经元分化水平较低）。此外，GPR137 KO 细胞表现出细胞周期调节因子细胞周期蛋白 D1 的表达增加，以及神经元分化标记物 NeuroD1 的表达减少。此外，GPR137 KO 细胞表现出较低的神经突生长标志物 STAT3 和 GAP43 的表达水平。这些表型在救援细胞中全部被消除。总之，GPR137缺失增加了细胞增殖并减少了神经元分化，表明GPR137促进了 Neuro2A 细胞的细胞周期退出和神经元分化。GPR137对神经元分化的调节对于大脑发育过程中神经元结构的构建至关重要。

图形概要