Morphogen gradients - New insights from DPP

The Drosophila TGF beta family member Decapentaplegic (DPP) has been propos ed to function as a morphogen to pattern cell fields in a number of develop mental contexts. A series of recent: reports add significantly to our knowl edge of the mechanisms of DPP-gradient formation and interpretation. These reports identify additional genes and genetic circuitry necessary for this patterning system, and they highlight variations that might reflect develop mental constraints within individual target cell fields.