FOXJ1 is a forkhead domain transcription factor essential for motile cilia formation and development. It acts as a master regulator of ciliogenesis by activating transcription of genes mediating ciliary assembly, including CFAP157 and ADGB 1. FOXJ1 binds specific DNA consensus sequences to drive expression of ciliary proteins in developing brain and lung tissues 2. Mechanistically, FOXJ1 expression is regulated by STAT-6 and IL-13 signaling; IL-13 suppresses FOXJ1 expression through STAT-binding elements in its promoter, leading to loss of ciliated cells and impaired mucociliary clearance 3. Additionally, FOXJ1 function can be disrupted via the tryptase-PAR2-FoxJ1 pathway, where mast cell-derived tryptase impairs choroid plexus epithelial cilia through FoxJ1 inhibition, increasing cerebrospinal fluid production in tumor-associated hydrocephalus 4. FoxJ1 mutations cause primary ciliary dyskinesia, a debilitating inherited motile ciliopathy affecting respiratory function 2. Beyond motile cilia, recent evidence reveals FOXJ1 regulates olfactory cilia biogenesis and olfactory sensory neuron differentiation, controlling expression of olfactory marker protein (omp) and odor-evoked signal transduction 5. Therapeutically, IL-4Rα inhibition (dupilumab) partially restores FOXJ1-dependent ciliation in severe asthma despite IL-13-induced remodeling 6.