Developmental Biomedical Science, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5, Takayama-cho, Ikoma 630-0192, Japan.
Department of Regenerative Medicine and Stem Cell Biology, Faculty of Medicine, University of Tsukuba, Tsukuba 305-8575, Japan.
Development. 2019 Sep 12;146(17):dev176784. doi: 10.1242/dev.176784.
Dorsal-ventral pattern formation of the neural tube is regulated by temporal and spatial activities of extracellular signalling molecules. Sonic hedgehog (Shh) assigns ventral neural subtypes via activation of the Gli transcription factors. Shh activity in the neural progenitor cells changes dynamically during differentiation, but the mechanisms regulating this dynamicity are not fully understood. Here, we show that temporal change of intracellular cAMP levels confers the temporal Shh signal, and the purinergic G-protein-coupled receptor GPR17 plays an essential role in this regulation. GPR17 is highly expressed in the ventral progenitor regions of the neural tube and acts as a negative regulator of the Shh signal in chick embryos. Although the activation of the GPR17-related signal inhibits ventral identity, perturbation of expression leads to aberrant expansion of ventral neural domains. Notably, perturbation of expression partially inhibits the negative feedback of Gli activity. Moreover, GPR17 increases cAMP activity, suggesting that it exerts its function by inhibiting the processing of Gli3 protein. GPR17 also negatively regulates Shh signalling in neural cells differentiated from mouse embryonic stem cells, suggesting that GPR17 function is conserved among different organisms. Our results demonstrate that GPR17 is a novel negative regulator of Shh signalling in a wide range of cellular contexts.
神经管的背腹模式形成受细胞外信号分子的时空活性调节。Sonic hedgehog（Shh）通过激活 Gli 转录因子来指定腹侧神经亚型。Shh 在神经祖细胞中的活性在分化过程中动态变化，但调节这种动态性的机制尚不完全清楚。在这里，我们表明细胞内 cAMP 水平的时间变化赋予了时间 Shh 信号，嘌呤能 G 蛋白偶联受体 GPR17 在这种调节中起着至关重要的作用。GPR17 在神经管的腹侧祖细胞区域中高度表达，并在鸡胚中作为 Shh 信号的负调节剂发挥作用。虽然 GPR17 相关信号的激活抑制了腹侧特征，但对 表达的扰动导致腹侧神经区域的异常扩张。值得注意的是，对 表达的扰动部分抑制了 Gli 活性的负反馈。此外，GPR17 增加了 cAMP 活性，表明它通过抑制 Gli3 蛋白的加工来发挥作用。GPR17 还在从小鼠胚胎干细胞分化的神经细胞中负调节 Shh 信号，表明 GPR17 功能在不同生物体中是保守的。我们的结果表明，GPR17 是广泛细胞环境中 Shh 信号的新型负调节剂。
