< i > Mms19 < /i > promotes spindle microtubule assembly in < i > Drosophila < /i > neural stem cells

by Rohan Chippalkatti, Boris Egger, Beat Suter Mitotic divisions depend on the timely assembly and proper orientation of the mitotic spindle. Malfunctioning of these processes can considerably delay mitosis, thereby compromising tissue growth and homeostasis, and leading to chromosomal instability. Loss of functionalMms19 drastically affects the growth and development of mitotic tissues inDrosophila larvae and we now demonstrate thatMms19 is an important factor that promotes spindle and astral microtubule (MT) growth, and MT stability and bundling.Mms19 function is needed for the coordination of mitotic events and for the rapid progression through mitosis that is characteristic of neural stem cells. Surprisingly,Mms19 performs its mitotic activities through two different pathways. By stimulating the mitotic kinase cascade, it triggers the localization of the MT regulatory complex TACC/Msps (Transforming Acidic Coiled Coil/Minispindles, the homolog of human ch-TOG) to the centrosome. This activity of Mms19 can be rescued by stimulating the mitotic kinase cascade. However, other aspects of theMms19 phenotypes cannot be rescued in this way, pointing to an additional mechanism ofMms19 action. We provide evidence that Mms19 binds directly to MTs and that this stimulates MT stability and bundling.
Source: PLoS Genetics - Category: Genetics & Stem Cells Authors: Source Type: research