Department of Human Molecular Genetics, University of Heidelberg, Heidelberg, Germany.
PLoS One. 2011;6(5):e19887. doi: 10.1371/journal.pone.0019887. Epub 2011 May 31.
Slit-Robo signaling guides commissural axons away from the floor-plate of the spinal cord and into the longitudinal axis after crossing the midline. In this study we have evaluated the role of the Slit-Robo GTPase activating protein 3 (srGAP3) in commissural axon guidance using a knockout (KO) mouse model. Co-immunoprecipitation experiments confirmed that srGAP3 interacts with the Slit receptors Robo1 and Robo2 and immunohistochemistry studies showed that srGAP3 co-localises with Robo1 in the ventral and lateral funiculus and with Robo2 in the lateral funiculus. Stalling axons have been reported in the floor-plate of Slit and Robo mutant spinal cords but our axon tracing experiments revealed no dorsal commissural axon stalling in the floor plate of the srGAP3 KO mouse. Interestingly we observed a significant thickening of the ventral funiculus and a thinning of the lateral funiculus in the srGAP3 KO spinal cord, which has also recently been reported in the Robo2 KO. However, axons in the enlarged ventral funiculus of the srGAP3 KO are Robo1 positive but do not express Robo2, indicating that the thickening of the ventral funiculus in the srGAP3 KO is not a Robo2 mediated effect. We suggest a role for srGAP3 in the lateral positioning of post crossing axons within the ventrolateral funiculus.
缝隙 - Robo 信号引导连合纤维离开脊髓基板并在中线交叉后进入纵轴。在这项研究中，我们使用基因敲除 (KO) 小鼠模型评估了缝隙 - Robo GTP 酶激活蛋白 3 (srGAP3) 在连合纤维导向中的作用。共免疫沉淀实验证实 srGAP3 与缝隙受体 Robo1 和 Robo2 相互作用，免疫组织化学研究表明 srGAP3 与 Robo1 在腹侧和外侧束中以及 Robo2 在外侧束中共定位。已报道在缝隙和 Robo 突变脊髓基板中的阻滞轴突，但我们的轴突追踪实验未显示 srGAP3 KO 小鼠基板中的背侧连合纤维轴突阻滞。有趣的是，我们观察到 srGAP3 KO 脊髓中的腹侧束明显增厚，外侧束变薄，这也最近在 Robo2 KO 中报道过。然而，srGAP3 KO 中增大的腹侧束中的轴突是 Robo1 阳性的，但不表达 Robo2，表明 srGAP3 KO 中腹侧束的增厚不是 Robo2 介导的效应。我们建议 srGAP3 在交叉后轴突在腹侧外侧束中的侧向定位中发挥作用。
