Mhox and vertebrate skeletogenesis: The long and the short of it

The development of the vertebrate skeleton is under complex genetic control, and good progress is being made towards identifying the genes responsible. A recent paper contributes to this progress by describing transgenic mice in which the homeobox-containing MHox gene has been disrupted. MHox(-/-) mice have a range of skeletal defects, involving loss or shortening of structures in the skull, face and limb. Puzzling features of the MHox(-/-) mutation, which has similar effects on bones with very different embryological origins and yet spares other bones completely, may hold clues to the mechanisms that shape the skeleton. MHox(-/-) mice, used in conjunction with other skeletal mutants, will be important tools for exploring these mechanisms further.