Speedy versus sluggish cells

Brain building H ow your brain grows might come down to how your cells divide. Lake and Sokol report that mouse protein Vangl2 controls the asymmetrical cell division and developmental fate of progenitor neurons. Vangl2 (aka Strabismus in fl ies) is a component of the PCP (planar cell polarity) pathway that is active in a variety of tissues and organisms. Mice that lack Vangl2 have a number of neurological defects including incomplete neural tube closure and reduced brain size. Lake and Sokol wondered how Vangl2 might infl uence brain development. In the cerebral cortex, neurons are born from a pool of progenitor cells, and the time of their birth determines their fate. The research duo found that Vangl2-lacking mouse embryos had large numbers of early-born neurons and few remaining progenitor cells. This hinted that Vangl2-lacking neurons were differentiating prematurely—a suspicion confi rmed in vitro. The progenitor pool is maintained by asymmetrical division— one daughter cell becomes a neuron, the other self-renews. This fate asymmetry is thought to depend on the orientation of cell division, and the authors observed an increase in the number of symmetrically dividing progenitors in the brains of Vangl2-lacking mouse embryos. Also, Vangl2-lacking cells in culture showed symmetrical distribution of a spindle-orienting factor that in normal cells distributes asymmetrically. Such similarities between Vangl2-lacking cells in vitro and in vivo will facilitate ongoing studies of the PCP pathway in neurogenesis. S ome cells live a fast-paced life, traveling far and wide. Others are more sedentary and stay closer to home. Ou and Vale now report molecular differences that underlie these lifestyle choices. Cell migration studies in living multicellular organisms are not easy. Ou and Vale used spinning disc confocal microscopy—a technique that allows fi ne focusing and rapid image capture—to follow the paths of individual fl uorescent cells in the bodies of worms. Images were captured from up to 10 worms at once over a period of hours, and the microscope automatically moved to specifi c focal points for each cell in each worm. Because the worms (and cells) were alive and moving, however, Ou had to readjust the focal points every 15 minutes or so. The cells of interest were neuroblasts, which are known to vary in their migration distances. The authors now report that these cells also vary in their speed, and faster cells ultimately go farther. Compared with their sluggish sisters, fast cells boosted their …