MT-Nanotubes: Lifelines for Stem Cells Marc Amoyel, Erika A. Bach  Cell Stem Cell  Volume 17, Issue 2, Pages 133-134 (August 2015) DOI: 10.1016/j.stem.2015.07.004 Copyright © 2015 Elsevier Inc. Terms and Conditions

Figure 1 Schematic of the Apex of the Adult Drosophila Testis The interface between one hub cell and one GSC is boxed and enlarged at right. Hub cells secrete the BMP factor Dpp into the extracellular space. MT-based membrane protrusions, termed MT-nanotubes, emanate from GSCs and orient toward hub cells. Tkv, a BMP receptor, trafficks on these structures and becomes activated along the MT-nanotubes by secreted Dpp. This results in the phosphorylation, activation, and nuclear translocation of the Smad protein Mad (phosphoMad), which induces GSC self-renewal (circular arrow). Depletion of several IFT-B proteins from GSCs results in fewer and shorter nanotubes, with the consequence of less Tkv stimulation, reduced phosphoMad levels, and impaired self-renewal. By contrast, depletion of the kinesin Klp10A results in thicker nanotubes, augmented Tkv activation on MT-nanotubes, increased phosphoMad levels, and enhanced self-renewal. Cell Stem Cell 2015 17, 133-134DOI: (10.1016/j.stem.2015.07.004) Copyright © 2015 Elsevier Inc. Terms and Conditions