A new principle for control of organ size is discovered by using the mouse limb bud to study how signals signalling growth and expansion are terminated. A combination of mutations were identified that revealed an inhibitory loop whereby FGF signalling represses Gremlin1, these two factors being key positive signals in limb bud outgrowth. This inhibitory loop is triggered by a positive FGF/Shh loop, and this model differs from earlier published models.
- Jamie M. Verheyden
- Xin Sun
