Sonic hedgehog (Shh) signalling controls cellular differentiation in the neural tube by regulating a poorly defined gene regulatory network. To better understand this network, James Briscoe and colleagues have undertaken a genome-wide expression screen in chick neural tube and, on , they identify the forkhead transcription factor Foxj1 as an Shh target gene in this tissue. Foxj1, they report, is expressed in the chick and mouse neural tube in cells that constitute the floor plate (FP), a neural tube organising centre. Foxj1 expression is associated with the formation of long motile cilia in several cell types and, consistent with this, the authors show that chick and mouse FP cells produce primary cilia longer than those produced elsewhere in the neural tube. Finally, they show that Foxj1 expression in the neural tube attenuates Shh signal transduction by altering cilia structure and modifying the intracellular localisation of the Gli proteins that mediate Shh signalling. Together, these data reveal a novel cilia-dependent mechanism that modulates cellular responses to Shh signalling.
