The Forkhead protein, FoxJ1, specifies node-like cilia in Xenopus and Zebrafish embryos

Ciliated cells that produce a leftward fluid flow have been proposed to mediate left-right patterning in many vertebrate embryos. The cilia on these cells combine features of primary sensory and motile cilia, but how this cilia subtype is specified is unknown. We address this issue by analyzing the Xenopus and Zebrafish homologs of FoxJ1, a forkhead transcription factor necessary for ciliogenesis in multi-ciliate cells of the mouse. We show that the cilia that underlie left-right patterning on the Xenopus gastrocoel roof plate (GRP) and Zebrafish Kupffer's vesicle (KV) are severely shortened or fail to form in FoxJ1 morphants. We also show that misexpressing XFoxJ1 is sufficient to induce ectopic GRP-like cilia formation in frog embryos. Microarray analysis indicates that XFoxJ1 induces the formation of cilia by upregulating the expression of motile cilia genes. These results indicate that FoxJ1 is a critical determinant in specifying cilia used in left-right patterning.