Analysis of epithelial explants injected with the intracellular domain of Notch (ICD) to block the formation of multi-ciliate cells, either alone or along with FoxJ1. FoxJ1 misexpression leads to the induction fo ectopic cilia in Xenopus laevis epithelia. Results show which genes are affected by FoxJ1 during the induction of ectopic cilia. Ciliated cells that produce a leftward fluid flow have been proposed to mediate left-right patterning in many vertebrate embryos. These cilia combine features of primary sensory and motile cilia, but how such cilia are 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. Experiment Overall Design: 2-cell stage Xenopus embryos were injected with synthetic mRNA encoding ICD alone or along with FoxJ1. At stage 9/10 the presumptive ectoderm was cut off the embryo and cultured on a fibronectin coated coverslip. At stage 22 RNA was harvested from explants and used as the starting material for arrays.