Specification of neuronal identity in the embryonic CNS

One of the earliest and most crucial steps in the development of connectivity within the CNS is the acquisition of specific identities by developing neural cells. In this review, we discuss how a neural cell may come to acquire its unique identity and some of the genes that may be involved in this process. Experimental evidence suggests that ectodermal cells may pass through several phases at which their potential fates become progressively more restricted. An initial step occurs during neural induction when ectodermal cells become restricted to either a neural or non-neural fate. A little later in development, a further set of interactions determine which of the neural cells become postmitotic and begin a programme of differentiation. The differentiation phase may itself involve several steps at which the postmitotic neuron progressively advances towards its final identity.