Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, USA.
Department of Anatomy and Neurobiology, University of Puerto Rico, USA.
Dev Biol. 2014 Jan 15;385(2):316-27. doi: 10.1016/j.ydbio.2013.10.027. Epub 2013 Nov 4.
Collective cell migration is critical for normal development, tissue repair and cancer metastasis. Migration of the posterior lateral line primordium (pLLP) generates the zebrafish sensory organs (neuromasts, NMs). This migration is promoted by the leader cells at the leading edge of the pLLP, which express the G protein-coupled chemokine receptor Cxcr4b and respond to the chemokine Cxcl12a. However, the mechanism by which Cxc112a/Cxcr4b signaling regulates pLLP migration remains unclear. Here we report that signal transduction by the heterotrimeric G protein subunit Gβ1 is essential for proper pLLP migration. Although both Gβ1 and Gβ4 are expressed in the pLLP and NMs, depletion of Gβ1 but not Gβ4 resulted in an arrest of pLLP migration. In embryos deficient for Gβ1, the pLLP cells migrated in an uncoordinated fashion and were unable to extend protrusions at the leading front, phenocopying those in embryos deficient for Cxcl12a or Cxcr4b. A transplantation assay showed that, like Cxcr4b, Gβ1 is required only in the leader cells of the pLLP. Analysis of F-actin dynamics in the pLLP revealed that whereas wild-type leader cells display extensive actin polymerization in the direction of pLLP migration, counterparts defective for Gβ1, Cxcr4b or Cxcl12a do not. Finally, synergy experiments revealed that Gβ1 and Cxcr4b interact genetically in regulating pLLP migration. Collectively, our data indicate that Gβ1 controls migration of the pLLP, likely by acting downstream of the Cxcl12a/Cxcr4b signaling. This study also provides compelling evidence for functional specificity among Gβ isoforms in vivo.
细胞集体迁移对于正常发育、组织修复和癌症转移至关重要。后外侧线原基（pLLP）的迁移产生了斑马鱼的感觉器官（神经丘，NM）。这种迁移是由 pLLP 前缘的先导细胞促进的，这些先导细胞表达 G 蛋白偶联趋化因子受体 Cxcr4b，并对趋化因子 Cxcl12a 作出反应。然而，Cxc112a/Cxcr4b 信号转导调节 pLLP 迁移的机制尚不清楚。在这里，我们报告说，异三聚体 G 蛋白亚基 Gβ1 的信号转导对于适当的 pLLP 迁移是必不可少的。尽管 Gβ1 和 Gβ4 都在 pLLP 和 NM 中表达，但 Gβ1 的耗竭而不是 Gβ4 的耗竭导致 pLLP 迁移停滞。在 Gβ1 缺陷的胚胎中，pLLP 细胞以不协调的方式迁移，并且无法在前沿延伸突起，这与 Cxcl12a 或 Cxcr4b 缺陷的胚胎相似。移植实验表明，与 Cxcr4b 一样，Gβ1 仅在 pLLP 的先导细胞中是必需的。对 pLLP 中 F-肌动蛋白动力学的分析表明，尽管野生型先导细胞在 pLLP 迁移的方向上显示出广泛的肌动蛋白聚合，但 Gβ1、Cxcr4b 或 Cxcl12a 缺陷的对应物则没有。最后，协同实验表明，Gβ1 和 Cxcr4b 在调节 pLLP 迁移中在遗传上相互作用。总的来说，我们的数据表明 Gβ1 控制 pLLP 的迁移，可能是通过 Cxcl12a/Cxcr4b 信号转导的下游作用。这项研究还为体内 Gβ 同工型的功能特异性提供了有力的证据。
