We study signal transduction mechanisms in the context of development and disease. The zebrafish, with its optically transparent embryos and suitability for genetic research, is used as the major test organism and compared with the human system. We focus on the function of signal molecules and receptors that play a role in innate immunity, cancer cell migration and embryonic development. Our major objectives are to study how cells can distinguish between different signals (self and non-self) and to investigate how the recognition of these signals dynamically alters cellular polarity. The research integrates studies at multiple levels ranging from molecules and cells to functional organisms as illustrated in the figure. Therefore the section uses a strongly multidisciplinary approach involving techniques from cell biology, biophysics, biochemistry, functional genomics and bioinformatics.