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.