Retrograde neural circuit specification by target-derived neurotrophins and growth factors.

Neural circuit assembly during development involves a series of highly regulated steps. While genetically pre-determined programs play key roles in the early steps including neurogenesis, migration, and initial growth and guidance of axons; increasing evidence indicates that as the axons reach their targets, the late steps of neuronal differentiation and connectivity formation may be influenced or even specified by target-derived signals. Here we attempt to provide a brief synthesized review on the roles of retrograde neurotrophin and growth factor signaling in regulating the final stages of neural circuit specificity such as axonal projection, dendritic patterning, neurotransmitter phenotype acquisition, and synapse formation.