Dendrite microtubules are polarized with minus-end-out orientation in Drosophila neurons. Nucleation sites concentrate at dendrite branch points, but how they localize is not known. Using Drosophila, we found that canonical Wnt signaling proteins regulate localization of the core nucleation protein γTubulin (γTub). Reduction of frizzleds (fz), arrow (low-density lipoprotein receptor-related protein [LRP] 5/6), dishevelled (dsh), casein kinase Iγ, G proteins, and Axin reduced γTub-green fluorescent protein (GFP) at branch points, and two functional readouts of dendritic nucleation confirmed a role for Wnt signaling proteins. Both dsh and Axin localized to branch points, with dsh upstream of Axin. Moreover, tethering Axin to mitochondria was sufficient to recruit ectopic γTub-GFP and increase microtubule dynamics in dendrites. At dendrite branch points, Axin and dsh colocalized with early endosomal marker Rab5, and new microtubule growth initiated at puncta marked with fz, dsh, Axin, and Rab5. We propose that in dendrites, canonical Wnt signaling proteins are housed on early endosomes and recruit nucleation sites to branch points.

中文翻译：

---

内体Wnt信号蛋白控制树突中的微管成核。

果蝇神经元中的负端取向使树突微管极化。成核位点集中在枝晶的分支点，但如何定位尚不清楚。使用果蝇，我们发现经典的Wnt信号蛋白调节核心成核蛋白γTubulin（γTub）的本地化。减少毛躁（fz），箭头（低密度脂蛋白受体相关蛋白[LRP] 5/6），蓬乱（dsh），酪蛋白激酶Iγ，G蛋白和Axin减少分支处的γTub-绿色荧光蛋白（GFP）点和树突状核的两个功能性读数证实了Wnt信号蛋白的作用。dsh和Axin都位于分支点，而dsh在Axin的上游。此外，将Axin绑定到线粒体足以招募异位γTub-GFP并增加树突中的微管动力学。在树突分支点，Axin和dsh与早期的内体标记Rab5共定位，并且新的微管生长在标有fz，dsh，Axin和Rab5的点处开始。我们建议在树突中，规范的Wnt信号蛋白被安置在早期的内体中，并招募成核位点至分支点。