Cilia signaling

It takes well-built cilia to send developmental signals on their way, show Tamara Caspary, Kathryn Anderson (Sloan-Kettering Institute, New York, NY), and Christine Larkins (Emory University, Atlanta, GA). Cilia that lack the correct internal architecture fail to transduce Hedgehog (Hh) signals correctly.

Hh signaling is particularly well-characterized in the developing nervous system. Depending on the amount of Hh activity, different types of neurons are produced. The particular type of neuron that forms is a result of the combination and amount of Hh-induced Gli transcription factors.

Caspary et al. now show that this neuronal choice is impaired in a mouse mutant called hennin, which has stumpy cilia. In these animals, different Hh levels were unable to increase or decrease Gli2 activity, which was stuck at a constitutively low level. As a result, one particular type...