In PLoS Biology this week, investigators at St. Jude Children's Research Hospital show that the homeobox gene "Prox1 is required for granule cell maturation and intermediate progenitor maintenance during brain neurogenesis." Specifically, Prox1 — expressed in the dentate gyrus during embryonic development and adult neurogenesis — is expressed in intermediate progenitors, and "required for adult neural stem cell self-maintenance in the sub-granular zone," the authors write.