Vesicles may help embryos take shape

Over the past decade, biologists have discovered a variety of chemicals whose

varying concentrations within an embryo set up the organism’s body plan. The researchers have thought that these so-called morphogens create chemical maps by

simply diffusing through an embryo.

Yet many morphogens tend to stick to cells, making it difficult to imagine the

chemicals diffusing for any distance. A new report suggests that morphogens may be

hitching long-distance rides in sacs made of cellular membranes. In the Sept. 7

Cell, Suzanne Eaton of the Max Planck Institute for Molecular Cell Biology and Genetics in Dresden, Germany, and her colleagues describe observations in fruit

fly embryos of vesicles that they dub argosomes. Moreover, the researchers found

that a morphogen called Wingless is almost always in parts of the embryo where

there are argosomes.

One way to prove that argosomes ferry morphogens across the embryo would be to

stop the vesicles in their tracks. At the moment, notes Craig Micchelli of Harvard

Medical School in Boston, “we don’t have a way to specifically disrupt these