Initiation of neural induction by FGF signalling before gastrulation

During neural induction, the 'organizer' of the vertebrate embryo instructs neighbouring ectodermal cells to become nervous system rather than epiderm is. This process is generally thought to occur around the mid-gastrula stag e of embryogenesis(1). Here we report the isolation of ERNI, an early respo nse gene to signals from the organizer (Hensen's node). Using ERNI as a mar ker, we present evidence that neural induction begins before gastrulation - much earlier in development than previously thought. We show that the orga nizer and some of its precursor cells produce a fibroblast growth factor si gnal, which can initiate, and is required for, neural induction.