IFT25 is a specialized component of the IFT-B complex mediating ciliary protein trafficking 1. Unlike most IFT proteins, IFT25 is not required for general ciliary assembly in somatic cells but plays a critical role in sonic hedgehog (SHH) signaling by forming a functional dimer with IFT27 that interfaces with the BBSome complex 23. This IFT25-IFT27 dimer binds the IFT74-IFT81 module and mediates export of membrane proteins, particularly GPCRs like Smoothened and GPR161, from cilia 23. IFT25 is essential for male fertility and sperm flagella development, with bidirectional trafficking dynamics occurring throughout spermatogenesis 4. In kidney development, IFT25 regulates early ureteric bud initiation rather than preventing cyst formation, with Ift25 mutations causing duplex kidneys and reduced branching morphogenesis 5. Clinically, impaired IFT25-IFT27-IFT74-IFT81 cooperation causes Bardet-Biedl syndrome-associated ciliary defects including abnormal ciliary protein accumulation and trafficking defects 36, indicating IFT25 dysfunction contributes to this ciliopathy spectrum.