Primary cilia and polycystic kidney disease

Situs inversus and polycystic kidney disease converge at primary cilia Although at first glance our body looks symmetrical, our internal organs obviously are arranged asymmetrically. It goes without saying that the heart is located on the left side and the liver on the right side yet such a seemingly trivial fact poses a very difficult biological question: How is the arrangement of the internal organs, the situs, regulated? Development of the organism starts with the fertilized oocyte, a round structure with no obvious asymmetry. At some point during development, however, axis formation occurs: A dorsal-ventral, an anterior-posterior and a leftright axis are established. Defects in left-right axis formation have been observed and are compatible with life, the patients suffer from situs inversus, i.e. their heart is located on the right side and the liver is located on the left side. As in many other circumstances, evidence obtained in the mouse has led to important insight into how the left-right axis may be for-