S elf reliance is not enough. Some organs rely on the kindness of others to control their size, according to Correct organ size is measured in mass, not cell numbers— forcing or blocking cell division generally does not change an organ's overall dimensions. Parker found the same is true in the fl y embryonic P compartment, which forms part of the larval epidermis. Increases in P compartment cel...

mTOR is the target of the immunosuppressive drug rapamycin and the central component of a nutrientand hormone-sensitive signaling pathway that regulates cell growth and proliferation. We now appreciate that this pathway becomes deregulated in many human cancers and has an important role in the control of metabolism and aging. We have identified two distinct mTORcontaining proteins complexes, on...

Systems biology seeks not only to discover the machinery of life but to understand how such machinery is used for control, i.e., for regulation that achieves or maintains a desired, useful end. This sort of goal-directed, engineering-centered approach also has deep historical roots in developmental biology. Not surprisingly, developmental biology is currently enjoying an influx of ideas and met...

A recently described knockout mouse has abnormally large muscles. The phenotype suggests that the ablated product, growth differentiation factor 8 or 'myostatin', may be one of the long sought inhibitors that control the growth of individual tissues and organs.