Foxj1 (forkhead-box J1), also known as hepatocyte nuclear factor-3 (HNF-3) or forkhead homologue-4 (HFH-4), is a member of the forkhead-box transcription factor family, a class of transcription factors with a winged helix structure that binds to DNA. The Foxj1 factor plays a major regulatory role in controlling the transcription process of motile cilia synthesis. Airway cilia quickly clear airway mucus by swinging, playing a role in resisting pathogen invasion. It also has an effect on the left-right axis asymmetry of organ development during the embryonic period. Studies have shown that Foxj1 KO mice exhibit left-right asymmetric development and airway ciliated epithelium is lost in adult mice. The heterozygous Foxj1 KO mice are viable, while the homozygous mice are lethal.