"We focused on the Dishevelled gene family because from our previous work, we knew that these genes were involved in the development of hair cells within the inner ear of the embryo, and that the cilia-like structures at the edge of the hair cells behave in a similar fashion as those on the node of the embryo. That similarity made us take a closer look at how this gene family was acting on correct placement of the nodal cilia at this very early stage of development," Wynshaw-Boris explained.

Masakazu Hashimoto, a graduate student in the Hamada lab and the first author of the study, monitored the movement of cilia in live mouse embryos using a high-speed camera attached to a microscope and observed that the cilia's position actually changed as development proceeded. In the very earliest stages - before left-right symmetry breaking occurred - cilia were located in the center of the node cells; then, as development progressed, the cilia gradually moved to the back side of the cells.

The researchers compared cilia in normal mouse embryos to those in embryos with mutated versions of all three Dishevelled genes. They found that the cilia in the mutant embryos were misplaced on the node cells and therefore unable to produce a leftward flow of fluid.

"This discovery provides exciting information about how we are built the way we are at the most basic of levels: that is, how do we differentiate our left side from our right? Ultimately this determines how the heart ends up on the left side of the body and the liver on the right side, for example," Wynshaw-Boris added.

Source: University of California - San Francisco