Every little helps

suggested a figure of 60 — that a chart of their activities would be as unappealingly complicated as a chart of intermediary metabolism. His prediction of the number of motor proteins has turned out to be disturbingly accurate (how did he do it?), though the charts have remained appealing. The significance of all this is that there are movements within cells, and motors responsible for them, that were undreamed of. Everything is moving all the time. Working all of this out will take some time, and should remain interesting for a long time to come. Some payoffs have already come in our understanding of chromosome segregation, which has proven to involve much more complex forms of motility than anticipated, and which has led to the identification of new and more specific targets for anti-proliferation drugs. In our own work we have made the surprising observation that cytoplasmic dynein, in addition to its clear roles in intracellular transport, is essential to cell migration. Through the skills of an outstanding current student, Jin-Wu Tsai, we are now able to inhibit dynein in developing brain and follow the effects on cell migration and division in brain slices. We can even image microtubules and other subcellular structures in situ in live migrating cells, which has us thinking that we are seeing the beginning of a brand new chapter in cell biology.