Sang Xianpeng, Curran Matthew S, Wood Antony W
Vincent Center for Reproductive Biology, Vincent Obstetrics and Gynecology Service, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, THR 933, Boston, Massachusetts 02114, USA.
Endocrinology. 2008 Oct;149(10):5035-42. doi: 10.1210/en.2008-0534. Epub 2008 Jun 19.
IGF signaling has been shown to stimulate migration of multiple cell types in vitro, but few studies have confirmed an equivalent function for IGF signaling in vivo. We recently showed that suppression of IGF receptors in the zebrafish embryo disrupts primordial germ cell (PGC) migration, but the mechanism underlying these effects has not been elucidated. We hypothesized that PGCs are intrinsically dependent upon IGF signaling during the migratory phase of development. To test this hypothesis, we first examined the spatial expression patterns of IGF ligand genes (igf1, igf2a, and igf2b) in the zebrafish embryo. In situ analyses revealed distinct expression patterns for each IGF ligand gene, with igf2b mRNA expressed in a spatial pattern that correlates strongly with PGC migration. To determine whether PGC migration is responsive to IGF signaling in vivo, we synthesized gene hybrid expression constructs that permit conditional overexpression of IGF ligands by PGCs into the PGC microenvironment. Conditional overexpression of IGF ligands consistently disrupted PGC migration, confirming that PGC migration is sensitive to local aberrations in IGF signaling. Finally, we show that conditional suppression of IGF signaling, via PGC-specific overexpression of a mutant IGF-I receptor, disrupts PGC migration, confirming that zebrafish PGCs intrinsically require IGF signaling for directional migration in vivo. Collectively, these studies confirm an in vivo role for IGF signaling in cell migration and identify a candidate ligand gene (igf2b) regulating PGC migration in the zebrafish.
胰岛素样生长因子（IGF）信号通路已被证明在体外可刺激多种细胞类型的迁移，但很少有研究证实IGF信号通路在体内具有同等功能。我们最近发现，斑马鱼胚胎中IGF受体的抑制会破坏原始生殖细胞（PGC）的迁移，但其潜在机制尚未阐明。我们推测，在发育的迁移阶段，PGC本质上依赖于IGF信号通路。为了验证这一假设，我们首先检测了斑马鱼胚胎中IGF配体基因（igf1、igf2a和igf2b）的空间表达模式。原位分析揭示了每个IGF配体基因的独特表达模式，其中igf2b mRNA的表达空间模式与PGC迁移密切相关。为了确定PGC迁移在体内是否对IGF信号通路有反应，我们合成了基因杂交表达构建体，使PGC能够在PGC微环境中条件性过表达IGF配体。IGF配体的条件性过表达持续破坏PGC迁移，证实PGC迁移对IGF信号通路的局部异常敏感。最后，我们表明，通过PGC特异性过表达突变型IGF-I受体对IGF信号通路进行条件性抑制会破坏PGC迁移，证实斑马鱼PGC在体内定向迁移本质上需要IGF信号通路。总的来说，这些研究证实了IGF信号通路在细胞迁移中的体内作用，并鉴定出一个调节斑马鱼PGC迁移的候选配体基因（igf2b）。
