Centrosomes lead stem cell orientation

Stem cells in the fly male germ line can both maintain their numbers and produce differentiating progeny by correctly orienting cell division, according to Yukiko Yamashita, D. Leanne Jones, and Margaret Fuller (Stanford University, Stanford, CA).

Asymmetric cell division is associated with control over spindle orientation in several models, such as the fly neuroblast and the worm P1 cell. In both of these cases, the spindle is reoriented during mitosis. But in fly germline stem cells (GSCs), which divide asymmetrically to produce one stem cell and one cell that initiates differentiation, Fuller's group now shows that the GSCs are oriented throughout the cell cycle, not just during mitosis.GSCs align themselves with the surface of their niche, known as the hub—a cluster of somatic cells in the testes...