Development—the process of building a body, starting from a single cell—is a carefully choreographed dance in which every participant must perform the right actions at the right moments or else the entire progression will go awry. Different groups of cells communicate using protein signals to coordinate their actions, because, if they do not, then, like a dancer leaping before their partner is ready to catch them, they will fall short of their goal—in this case, building a working body. Researchers in Whitehead Institute Director Ruth Lehmann’s lab wanted to better understand the different groups of cells involved in creating the gonads—the reproductive organs—and in guiding development of the germ cells, the set of cells that become eggs and sperm. In work published in Developmental Cell on June 2, Lehmann lab postdoc Torsten Banisch showed that an unexpected type of cell, the swarm cells, relay a hormone signal to the germ cell precursors, known as primordial germ cells, which prompts them to differentiate and give rise to the eggs. Swarm cells were first identified almost two decades ago, but until now their function has been unknown.
