Left-right axis determination.

Vertebrates display left-right (L-R) asymmetric organ positioning and morphologies, which are established during embryonic development. These asymmetries are conserved among individuals and species. How, when and where do embryos first break the symmetry? Why is it broken in a consistent direction? How is the asymmetry transmitted to and coordinated within the whole embryo? Which of these elements are conserved between different organisms? These questions have been the focus of intense research during the last decade, and much has been learned. Nonetheless, our understanding of how tissue and organ L-R differences are established during embryogenesis is scarce. A systems biology approach may enable us to better understand the dynamics of gene networks, epigenetics, cilia, fluids, and charged molecules as well as other processes involved in the generation of the vertebrate L-R axis.