Each of us is a marvel of spontaneous organization: A single fertilized egg gave rise to a complex system of specialized tissues and properly located organs. Researchers at Boston's Forsyth Institute and at Harvard University have taken a big step toward explaining this process. When an embryo consists of just four cells, they have found, an electric gradient starts switching on the genes that distinguish left from right.
"We knew that something was instigating differential gene expression, serving as a master blueprint for development, and we had a hunch it happened right from the get-go," says biologist Michael Levin of the Forsyth Institute. He and his colleagues used a voltage-sensitive fluorescent dye to trace an electric potential across frog and chick embryos. The researchers identified the mechanism responsible for this electrical gradient: a tiny ion pump on the surface of the cells. The pump is localized on one side of ...
