Institute of Genetics and Biophysics Adriano Buzzati-Traverso, Naples Italy.
PLoS One. 2012;7(2):e30661. doi: 10.1371/journal.pone.0030661. Epub 2012 Feb 17.
Due to their correlation with major human neurological diseases, dopaminergic neurons are some of the most studied neuronal subtypes. Mesencephalic dopaminergic (mDA) differentiation requires the activation of a cascade of transcription factors, among which play a crucial role the nuclear receptor Nurr1 and the paired-like homeodomain 3, Pitx3. During development the expression of Nurr1 precedes that of Pitx3 and those of typical dopaminergic markers such as tyrosine hydroxylase (TH) and dopamine Transporter (DAT) that are directly regulated by Nurr1. Interestingly we have previously demonstrated that Nurr1 RNA silencing reduced Pitx3 transcripts, leading to the hypothesis that Nurr1 may control Pitx3 expression.Here we show that Nurr1 overexpression up-regulates that of Pitx3 in a dose-dependent manner by binding to a non-canonical NBRE consensus sequence, located at the 5' site of the gene. Interestingly, this sequence shows the same effect as the canonical one in promoting gene translation, and its deletion abolishes the ability of Nurr1 to sustain reporter gene expression. Moreover, we show that there is a direct interaction between Nurr1 and the Pitx3 gene promoter in dopaminergic cell cultures and midbrain embryonic tissue. Altogether, our results suggest that the regulation of Pitx3 by Nurr1 may be an essential event controlling the development and function of mDA neurons.
由于与人类重大神经疾病相关，多巴胺能神经元是研究最多的神经元亚型之一。中脑多巴胺能（mDA）分化需要一系列转录因子的激活，其中核受体 Nurr1 和同源盒蛋白 3（Pitx3）起着至关重要的作用。在发育过程中，Nurr1 的表达先于 Pitx3 和其他典型的多巴胺能标志物，如酪氨酸羟化酶（TH）和多巴胺转运蛋白（DAT）的表达，这些标志物直接受 Nurr1 调控。有趣的是，我们之前已经证明，Nurr1 RNA 沉默会减少 Pitx3 转录物，这导致了 Nurr1 可能控制 Pitx3 表达的假设。在这里，我们展示 Nurr1 过表达以剂量依赖的方式上调 Pitx3 的表达，通过与基因 5' 位点的非典型 NBRE 共有序列结合。有趣的是，该序列与促进基因翻译的典型序列具有相同的效果，其缺失会削弱 Nurr1 维持报告基因表达的能力。此外，我们还证明在多巴胺能细胞培养物和中脑胚胎组织中，Nurr1 和 Pitx3 基因启动子之间存在直接相互作用。总之，我们的结果表明，Nurr1 对 Pitx3 的调节可能是控制 mDA 神经元发育和功能的一个重要事件。
