Membrane Palmitoylated Protein 7 is Required for Osteogenesis and is Linked with Bone Mineralization and Osteoporosis: The Functional Evaluation of GEFOS GWAS Hit.

Oct 17, 2025Calcified tissue international

How a Key Protein Affects Bone Growth and Osteoporosis

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Abstract

Research has shown that certain genes are linked to bone density, which is important for preventing fractures in osteoporosis. One such gene, called MPP7, is crucial for bone health but its role wasn't well understood. This study found that MPP7 levels were much lower in the bones of people with osteoporosis compared to those without. By using a gene-editing technique, researchers discovered that when MPP7 is removed from bone cells, these cells struggle to grow and mineralize properly, which is vital for strong bones. This suggests that MPP7 is important for bone cell function and may be linked to osteoporosis risk in humans.

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Genome-wide association studies have identified multiple loci associated with bone mineral density, a major determinant of osteoporotic fracture risk. At one such locus, genetic, bioinformatic, and zebrafish knockout data strongly prioritize membrane palmitoylated protein 7 (MPP7) as a candidate gene, although its precise role in bone biology remains poorly defined. MPP7 encodes a member of the p55 Stardust family of membrane-associated guanylate kinase proteins, which are key regulators of epithelial cell polarity and junctional organization. Here, we investigated the functional role of MPP7 in bone biology. We found that MPP7 expression was significantly reduced-by approximately twofold-in bone tissue from osteoporotic patients compared with osteoarthritic patients and non-osteoporotic controls. Furthermore, we generated a CRISPR/Cas9-mediated MPP7 knockout in the human osteosarcoma HOS cell line and demonstrated that MPP7 deletion impairs osteogenic differentiation and completely abrogates mineralization through downregulation of ALPL expression. Knockout cells also displayed altered morphology, suggesting that MPP7 influences osteoblast function via effects on cell polarity and adhesion. Collectively, our findings, together with zebrafish genetic evidence, indicate that MPP7 plays a critical role in osteoblast differentiation and mineralization and may contribute to osteoporosis susceptibility in humans.

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