Plays an important role in bone formation and normal bone mineralization. Promotes the differentiation of myoblasts into osteoblasts (PubMed:20025746). May induce the commitment and differentiation of myoblasts into osteoblasts through an enhancement of BMP2 production and interaction with the BMP-RUNX2 pathway. Up-regulates the expression of ATF4, a transcription factor which plays a central role in osteoblast differentiation. Essential for normal spermatogenesis and late testicular differentiation (By similarity). Interacts with SMAD1, SMAD5 and RUNX2. Expressed in brain microglia (at protein level). Elevated expression levels seen in the brain of patients with Alzheimer disease. Expressed by osteoblast-like cells in bone tissues and follicular dendritic cells in lymphoid tissues.