Positive and negative regulation of developmental signaling by the endocytic pathway.

Multicellular organisms acquire complex architecture through highly regulated developmental processes in which cells are programmed to respond to a specific set of extracellular signals produced by themselves and others. Modulation of sensitivity or duration of response is controlled by a variety of intracellular mechanisms. The endoocytic pathway performs essential regulatory roles both for the activation as well as the inactivation of signal transduction. Early stage of endocytic pathway is required for the recruitment of cytosolic mediators for signal amplification of signaling, whereas signal termination by late endosomes/lysosomes is important for spatiotemporal regulation. Herein, we summarize recent studies showing that dysfunction in endocytic pathways causes patterning defects in early embryogenesis in mammals.