Temporo-spatial interactions among blood vessels, nerve axons and myogenic cells govern the guidance of hypoglossal nerve in mouse tongue primordium

本研究旨在探讨舌下神经轴突生长在小鼠舌发育中的导向机制。对150~600个连续切片进行三维重建。取ICR小鼠E9.5~11.5胚胎连续切片，分别用Pecam 1、Desmin或Pgp 9.5-Gap 43抗体进行免疫双标记。所实现的3D重建保证了上级定位精度，以追踪血管和单个颅神经轴突的远程连接。舌下神经轴突长距离向舌原基迁移，与舌肌源性细胞紧密接触，毛细血管位于舌下神经轴突尖端附近。基因表达和蛋白定位分析表明，Cxcl 12和Cxcr 4信号来源于舌肌细胞和毛细血管，可能是舌下神经的轴突导向因子。

We aimed to investigate the guidance mechanism of growing hypoglossal nerve axons in mouse tongue development. 3D reconstruction was conducted using 150~600 serial sections. All serial sections, which were obtained from ICR mouse embryos at E9.5~11.5, were dual-immunolabeled with Pecam1, Desmin or Pgp9.5-Gap43 antibodies. The achieved 3D reconstructs warranted superior positional accuracy to trace the long-range connectivity of blood vessels and individual cranial nerve axons. The hypoglossal nerve axons, which uniquely underwent long-range migration toward tongue primordium, were in close contact with tongue myogenic cells that originated from the occipital somites, and the blood capillaries were localized at the vicinity of the tip of hypoglossal nerve axons. The analysis of gene expression and protein localization revealed that Cxcl12 and Cxcr4 signals, which originated from tongue myogenic cells and blood capillaries, may act as the axon guidance factors of the hypoglossal nerve.