Role of the captured retroviral envelope syncytin-B gene in the fusion of osteoclast and giant cell precursors and in bone resorption, analyzed ex vivo and in vivo in syncytin-B knockout mice

Bone Reports
Amélie E CoudertAnne Dupressoir

Abstract

Syncytin-A and -B are envelope genes of retroviral origin that have been captured in evolution for a role in placentation. They trigger cell-cell fusion and were shown to be essential for the formation of the syncytiotrophoblast layer during mouse placenta formation. Syncytin-A and -B expression has been described in other tissues and their highly fusogenic properties suggested that they might be involved in the fusion of other cell types. Here, taking advantage of mice knocked out for syncytin-B, SynB-/- mice, we investigated the potential role of syncytin-B in the fusion of cells from the monocyte/macrophage lineage into multinucleated osteoclasts (OCs) -in bone- or multinucleated giant cells -in soft tissues. In ex vivo experiments, a significant reduction in fusion index and in the number of multinucleated OCs and giant cells was observed as soon as Day3 in SynB-/- as compared to wild-type cell cultures. Interestingly, the number of nuclei per multinucleated OC or giant cell remained unchanged. These results, together with the demonstration that syncytin-B expression is maximal in the first 2 days of OC differentiation, argue for syncytin-B playing a role in the fusion of OC and giant cell mononucleated precursors, at initi...Continue Reading

Methods Mentioned

BETA
X-ray
urine collection
FACS
PCR
confocal microscopy
flow cytometry

Software Mentioned

NRecon
geNorm
Prism GraphPad
Zeiss LSM Image Browser
CTAn
Microvision

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