Organs such as the heart and gut are asymmetrical, but the mechanisms that control their development have been unclear. Two papers in 4 July
Shigenori Nonaka and colleagues at Osaka University, Japan, used murine embryos cultured under an artificial extracellular (nodal) fluid flow. They observed that a rightward flow that was sufficiently rapid to reverse the intrinsic leftward nodal flow resulted in reversal of situs in wild-type embryos. The artificial flow was also able to direct the situs of mutant mouse embryos with immotile cilia (
In the second paper, Jeffrey Essner and colleagues at the University of Utah, Salt Lake City, show that the existence of node monocilia and the expression of a dynein gene that is implicated in...