IFT80 and Osteopenia: Defects in IFT80 in osteoblast progenitor cells cause significant growth retardation and osteopenia associated with impaired osteoblast differentiation; IFT80 deficiency blocks cilia-dependent canonical Hh-Gli signaling and overactivates the cilia-independent non-canonical Hh-Gαi-RhoA pathway, which inhibits osteoblast differentiation.