Choose a side

Dividing an organism into unequal halves just took a giant step backward—in time, that is. Michael Levin, Mark Mercola (Harvard Medical School, Boston, MA), and colleagues have identified what is so far the earliest-acting determinant of left/right (LR) asymmetry. According to their findings, this early determinant establishes voltage differences that distinguish left from right.

Based on previous evidence that gap junctions are required for LR asymmetry, the group devised a simple model to explain how asymmetry determinants might be driven directionally through gap junctions in a process akin to electrophoresis. Though he did not necessarily believe the model, Mercola says, “the idea that voltage differences and channels or pumps may be important was testable.”

And tested it was. In what Mercola likes to call the...