The regulator of gene transcription, NF-κB, was first identified in the B cells of the immune system. A further function for it is emerging through studies of the chick limb, and two new papers show that NF-κB is on the signalling pathway that specifies correct limb development — when its activity is blocked, the result is truncated limbs. This line of research is all the more intriguing because of close parallels with development in the fruitflyDrosophila, and because mutations in one of the signalling targets of NF-κB, a gene called Twist, result in a human condition characterized by limb anomalies.
