Effect of a rare genetic variant of TM7SF4 gene on osteoclasts of patients with Paget’s disease of bone

Abstract

BackgroundDendritic Cell-Specific Transmembrane Protein (DC-STAMP) is involved in osteoclastogenesis with a key role in mononucleated osteoclasts fusion. We reported in patients with Paget’s disease of bone (PDB) a rare variant (rs62620995) in the TM7SF4 gene, encoding for DC-STAMP, which changes a highly conserved amino acid, possibly damaging according to in silico predictions. This study aimed at determining the functional effects of this variant on osteoclast phenotype in PDB.MethodsFifty ml of peripheral blood were collected in pagetic patients carrier of this variant (n = 4) or not (n = 4) and healthy controls (n = 4). Monocytes were collected after Ficoll gradient and cultured in a medium containing RANKL (40 ng/ml) and hMCSF (25 ng/ml). At the end of the differentiation period, we assessed the osteoclast morphology and bone resorption abilities. We quantified gene expression of SQSTM1, DC-STAMP, OS9, CREB3, LAMP1, OC-STAMP, and NFATC1 genes from cell lysates. Proteins encoded by these genes were investigated by Western Blot. Statistical analyses relied on ANOVA followed by Tukey post-tests.ResultsAfter 21 days of differentiation, the mean number of nuclei per multinucleated cell was significantly higher in pagetic patients carrier of the variant than in healthy controls. Bone resorption abilities were not modified by the variant. qPCR and Western Blot analyses did not provide any differences, but DC-STAMP expression was higher in patients carrier of the variant than in patients non carrier.ConclusionsThis TM7SF4 rare variant may have an impact on osteoclast morphology and on DC-STAMP expression during osteoclastogenesis. Further analyses are required to understand the role of this variant during osteoclastogenesis in PDB.Electronic supplementary materialThe online version of this article (10.1186/s12881-017-0495-3) contains supplementary material, which is available to authorized users.

CD13 is a critical regulator of cell–cell fusion in osteoclastogenesis

“…Clinically, Paget’s disease of the bone (PDB) is a disorder resulting from osteoclast overactivity of unknown etiology. Osteoclast-like cells isolated from PDB patients carrying a DC-STAMP genetic variant showed higher DC-STAMP expression levels and greater numbers of nuclei per cell compared to both healthy controls and PDB patients without the variant 40 . A distinct gain-of-function DC-STAMP variant (rs2458413) studied in cells from 158 patients was significantly associated with PDB 41 .…”

Common signalling pathways in macrophage and osteoclast multinucleation

“…It is often used as a cell-fusion marker in fusing MGCs and osteoclasts (Eleveld-Trancikova et al, 2005). Moreover, a genetic variant of the DCSTAMP gene was found to simulate osteoclastogenesis in patients with Paget's disease of bone (Laurier et al, 2017). Its downstream signalling in osteoclasts and FBGCs appears to be via the RANKL-NFATc1 and IL-4-STAT6-NF-κB axes, respectively (Yagi et al, 2005).…”

Osteoclast Multinucleation: Review of Current Literature

“…Beauregard et al identified a rare variant (rs62620995) of DC-STAMP, although this turned out to have only a marginal association with PDB [ 69 ]. Laurier et al later found that osteoclast-like cells from PDB patients carrying this variant showed higher expression levels of DC-STAMP and greater numbers of nuclei compared to both healthy controls and PDB patients without the variant, suggesting that these patients are more susceptible to PDB lesions [ 70 ]. Using cells from 158 PDB patients, Mullin et al observed that a gain-of-function variant (rs2458413) was significantly associated with PDB [ 71 ].…”