Mutation of the sequestosome 1 (p62) gene increases osteoclastogenesis but does not induce Paget disease
Noriyoshi Kurihara, Yuko Hiruma, Hua Zhou, Mark A. Subler, David W. Dempster, Frederick R. Singer, Sakamuri V. Reddy, Helen E. Gruber, Jolene J. Windle, G. David Roodman
Noriyoshi Kurihara, Yuko Hiruma, Hua Zhou, Mark A. Subler, David W. Dempster, Frederick R. Singer, Sakamuri V. Reddy, Helen E. Gruber, Jolene J. Windle, G. David Roodman
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Research Article Bone biology

Mutation of the sequestosome 1 (p62) gene increases osteoclastogenesis but does not induce Paget disease

Abstract

Paget disease is the most exaggerated example of abnormal bone remodeling, with the primary cellular abnormality in the osteoclast. Mutations in the p62 (sequestosome 1) gene occur in one-third of patients with familial Paget disease and in a minority of patients with sporadic Paget disease, with the P392L amino acid substitution being the most commonly observed mutation. However, it is unknown how p62P392L mutation contributes to the development of this disease. To determine the effects of p62P392L expression on osteoclasts in vitro and in vivo, we introduced either the p62P392L or WT p62 gene into normal osteoclast precursors and targeted p62P392L expression to the osteoclast lineage in transgenic mice. p62P392L-transduced osteoclast precursors were hyperresponsive to receptor activator of NF-κB ligand (RANKL) and TNF-α and showed increased NF-κB signaling but did not demonstrate increased 1,25-(OH)2D3 responsivity, TAFII-17 expression, or nuclear number per osteoclast. Mice expressing p62P392L developed increased osteoclast numbers and progressive bone loss, but osteoblast numbers were not coordinately increased, as is seen in Paget disease. These results indicate that p62P392L expression on osteoclasts is not sufficient to induce the full pagetic phenotype but suggest that p62 mutations cause a predisposition to the development of Paget disease by increasing the sensitivity of osteoclast precursors to osteoclastogenic cytokines.

Authors

Noriyoshi Kurihara, Yuko Hiruma, Hua Zhou, Mark A. Subler, David W. Dempster, Frederick R. Singer, Sakamuri V. Reddy, Helen E. Gruber, Jolene J. Windle, G. David Roodman

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Figure 6

Time course for OCL formation, OCL precursor proliferation, and OCL apoptosis by marrow cells from TRAP-p62P392L or WT mice.

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Time course for OCL formation, OCL precursor proliferation, and OCL apop...
(A) OCL precursors (105 cells/well) from TRAP-p62P392L and WT mice were cultured in the presence of RANKL or TNF-α. After 3, 6, or 9 days of culture, cells were fixed and number of TRAP-positive OCLs counted. (B) OCL precursors (1 × 106 per culture) from WT (white bars) and TRAP-p62P392L (black bars) littermate mice were cultured for 2, 4, or 6 days and were pulsed at the end of the culture period for 1 hour with 1 mCi [3H]-thymidine. Radioactivity was counted by liquid scintillation spectrometry. Results are expressed as the mean ± SD for quadruplicate cultures. *P < 0.001 compared with results of WT cultures treated with the same concentration of RANKL or TNF-α. (C) OCL precursors (105 cells/well) from TRAP-p62P392L and WT mice were cultured in the presence of RANKL or TNF-α. After 9 days of culture, cells were fixed and number of apoptotic OCLs were counted using a commercial Annexin V kit (Promega). All results are expressed as the mean ± SD for quadruplicate cultures.