Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115, Taiwan.
Department of Neurology, School of Medicine, College of Medicine, Taipei Medical University, Taipei 115, Taiwan.
Sci Rep. 2016 Jun 21;6:28297. doi: 10.1038/srep28297.
Cyclins play a central role in cell-cycle regulation; in mammals, the D family of cyclins consists of cyclin D1, D2, and D3. In Xenopus, only homologs of cyclins D1 and D2 have been reported, while a novel cyclin, cyclin Dx (ccndx), was found to be required for the maintenance of motor neuron progenitors during embryogenesis. It remains unknown whether zebrafish possess cyclin D3 or cyclin Dx. In this study, we identified a zebrafish ccndx gene encoding a protein which can form a complex with Cdk4. Through whole-mount in situ hybridization, we observed that zccndx mRNA is expressed in the motor neurons of hindbrain and spinal cord during development. Analysis of a 4-kb promoter sequence of the zccndx gene revealed the presence of HRE sites, which can be regulated by HIF2α. Morpholino knockdown of zebrafish Hif2α and cyclin Dx resulted in the abolishment of isl1 and oligo2 expression in the precursors of motor neurons, and also disrupted axon growth. Overexpression of cyclin Dx mRNA in Hif2α morphants partially rescued zccndx expression. Taken together, our data indicate that zebrafish cyclin Dx plays a role in maintaining the precursors of motor neurons.
细胞周期蛋白在细胞周期调控中起着核心作用；在哺乳动物中，D 家族的细胞周期蛋白包括细胞周期蛋白 D1、D2 和 D3。在非洲爪蟾中，仅报道了细胞周期蛋白 D1 和 D2 的同源物，而一种新型的细胞周期蛋白 cyclin Dx（ccndx）被发现对于胚胎发生期间运动神经元前体的维持是必需的。目前尚不清楚斑马鱼是否具有细胞周期蛋白 D3 或 cyclin Dx。在这项研究中，我们鉴定了一个斑马鱼 ccndx 基因，该基因编码的蛋白质可以与 Cdk4 形成复合物。通过整体原位杂交，我们观察到 zccndx mRNA 在发育过程中在后脑和脊髓的运动神经元中表达。对 zccndx 基因的 4kb 启动子序列的分析显示存在 HRE 位点，该位点可受 HIF2α 调控。斑马鱼 Hif2α 和 cyclin Dx 的 Morpholino 敲低导致运动神经元前体中 isl1 和 oligo2 表达的消除，并破坏了轴突生长。cyclin Dx mRNA 在 Hif2α 形态发生体中的过表达部分挽救了 zccndx 的表达。总之，我们的数据表明，斑马鱼 cyclin Dx 在维持运动神经元前体中起作用。
