FOXN4 is a forkhead box transcription factor located on chromosome 12.12 that functions as a key regulator of cellular differentiation and developmental patterning 1. The gene encodes multiple isoforms sharing conserved FOX and FN14 domains 1. During neural development, FOXN4 specifies amacrine and horizontal cell fates in the retina while suppressing photoreceptor fates through DLL4-NOTCH signaling activation, and cooperates with ASCL1 to drive V2b interneuron commitment in the spinal cord. In non-neural tissues, FOXN4 is essential for atrioventricular canal specification 2 and contributes to airway epithelial differentiation, where it marks deuterosomal precursors of multiciliated cells 3. Clinically, FOXN4 demonstrates tumor-suppressive functions. In breast cancer, elevated FOXN4 associates with improved prognosis and reduced proliferation, metastasis, and EMT through TP53 activation and Notch pathway inhibition 4. Conversely, miR-941-mediated FOXN4 downregulation promotes lung adenocarcinoma progression via altered neutrophil polarization and TGF-β signaling 5. In myocardial ischemia-reperfusion injury, FOXN4 knockdown alleviates cardiomyocyte ferroptosis through HIF-1α/MMP2 pathway inhibition 6. Evolutionary evidence suggests FOXN4 contributes to thymopoietic function in teleost fishes, with ancestral FOXN4 genes giving rise to mammalian FOXN1 7.