eLife assessment:
Bone marrow stromal cells (BMSCs) can differentiate into a variety of cell types such as osteoblasts, chondrocytes, and adipocytes. The authors of this important study provide compelling and strong evidence that ablating O-GlcNAc transferase (OGT) in BMSCs impairs bone formation but promotes marrow adiposity. The results show that the balance of osteogenic and adipogenic differentiation of BMSCs is controlled by reciprocal O-GlcNAc regulation of lineage-specifying transcription factors, and highlights the importance of an intracellular glycosylation process of specific proteins in bone formation and bone marrow adipocytes.