The Path to the Heart and the Road Not Taken

Understanding which molecules induce an embryonic precursor cell to become one tissue instead of another has long fascinated developmental biologists. In his Perspective, Olson describes new findings that identify the Wnt signaling molecules Wnt3a and Wnt8 as inhibitory factors produced by the neural tube that prevent embryonic mesoderm cells from becoming heart tissue and instead induce them to become blood.