Promotes osteoblast cell differentiation and terminal mineralization. Plays a role in inducing the cell cycle arrest via inhibiting CCND1 expression in all-trans-retinoic acid (ATRA) signal pathway. In osteoclasts, forms a transporter complex with ATRAID for nitrogen-containing-bisphophonates (N-BPs) required for releasing N-BP molecules that have trafficked to lysosomes through fluid-phase endocytosis into the cytosol (PubMed:29745899). . This is the function of Ensembl gene identifier ENSG00000138085 (ATRAID, all-trans retinoic acid induced differentiation factor).