Division of Life Sciences (Molecular Biology Major), Jeonbuk National University, Jeonju 54896, Korea.
Department of Bioactive Material Sciences and Research Center of Bioactive Materials, Jeonbuk National University, Jeonju 54896, Korea.
Mol Cells. 2020 Mar 31;43(3):228-235. doi: 10.14348/molcells.2019.0294.
The transmembrane semaphorin Sema-1a mediates forward and reverse signaling that plays an essential role in motor and central nervous system (CNS) axon pathfinding during embryonic neural development. Previous immunohistochemical analysis revealed that Sema-1a is expressed on most commissural and longitudinal axons in the CNS and five motor nerve branches in the peripheral nervous system (PNS). However, Sema-1a-mediated axon guidance function contributes significantly to both intersegmental nerve b (ISNb) and segmental nerve a (SNa), and slightly to ISNd and SNc, but not to ISN motor axon pathfinding. Here, we uncover three -regulatory elements (CREs), , and , that robustly drove reporter expression in a large subset of neurons in the CNS. In the transgenic lines and reporter expression was consistently observed on both ISNb and SNa nerve branches, whereas in the line reporter expression was irregularly detected on ISNb or SNa nerve branches in small subsets of abdominal hemisegments. Through complementation test with a Sema1a loss-of-function allele, we found that neuronal expression of Sema-1a driven by each of and restores robustly the CNS and PNS motor axon guidance defects observed in Sema-1a homozygous mutants. However, when wild-type Sema-1a is expressed by in mutants, the PNS axon guidance phenotypes are partially rescued while the CNS axon guidance defects are completely rescued. These results suggest that in a redundant manner, the CREs, , and govern the Sema-1a expression required for the axon guidance function of during embryonic neural development.
跨膜信号素 Sema-1a 介导正向和反向信号，在胚胎神经发育过程中对运动和中枢神经系统 (CNS) 轴突寻路至关重要。以前的免疫组织化学分析表明，Sema-1a 在中枢神经系统的大多数连合和纵轴突以及周围神经系统 (PNS) 的 5 个运动神经分支上表达。然而，Sema-1a 介导的轴突导向功能对间节神经 b (ISNb) 和节段神经 a (SNa) 有重要贡献，对 ISNd 和 SNc 略有贡献，但对 ISN 运动轴突寻路没有贡献。在这里，我们发现了三个调节元件 (CREs)， ， 和 ，它们在中枢神经系统的一大类神经元中强烈驱动报告基因的表达。在 和 转基因系中，报告基因表达一致地观察到在 ISNb 和 SNa 神经分支上，而在 线中，报告基因表达在一小部分腹部半节段的 ISNb 或 SNa 神经分支上不规则地检测到。通过与 Sema1a 功能缺失等位基因的互补测试，我们发现由每个 和 驱动的 Sema-1a 的神经元表达在 Sema-1a 纯合突变体中恢复了中枢神经系统和 PNS 运动轴突导向缺陷的稳健性。然而，当野生型 Sema-1a 由 在 突变体中表达时，PNS 轴突导向表型部分恢复，而 CNS 轴突导向缺陷完全恢复。这些结果表明，在冗余方式下，CREs ， ，和 控制了 Sema-1a 的表达，这是 Sema-1a 在胚胎神经发育过程中对轴突导向功能所必需的。
