Transcription factor that acts as a key regulator of ciliogenesis. Specifically regulates expression of genes required for cilium assembly and function. Recognizes and binds the X-box, a regulatory motif with DNA sequence 5'-GTNRCC(0-3N)RGYAAC-3' present on promoters (PubMed:22227339, PubMed:24424412). Required for neural tube closure and neural ciliogenesis (PubMed:22227339). Homodimer. Heterodimer; heterodimerizes with other rfx proteins. Mainly expressed in the nucleus and at lower level in cytoplasm. Preferentially expressed in ciliated tissues, such as neural tube, gastrocoel roof plate, epidermal multiciliated cells, otic vesicles and kidneys. Belongs to the RFX family.