A NOVEL METHOD TO IDENTIFY OSTEOCLAST FUSION REGULATING GENES

Osteoclasts are bone resorbing cells derived from the monocyte-macrophage lineage. Enhanced activity of osteoclasts which results in net bone loss and fragility fractures underlies the pathologic mechanism of many bone diseases such as osteoporosis. Thus, inhibition of osteoclast activity is a desired outcome for the treatment of many metabolic bone disorders. Osteoclasts differentiation involves fusion of precursor cells which generate a multinucleated cell with high bone resorption capability. Although several osteoclast fusion regulatory genes have been discovered, little is known about the fusion process and its role in bone pathologies.

In order to identify new genes which effects cell fusion, we developed a novel method to screen for osteoclast fusion regulating genes. This screen is based on nuclear staining by different fluorescent proteins. We have used this method to screen 330 mouse kinases and discovered 40 novel fusion regulating kinases. Through validation and elimination process we identified Dyrk2 as a novel regulator of osteoclast fusion. We further show that knock-down of Dyrk2 expression in primary cells promotes both osteoclasts and macrophage cell fusion, suggesting a negative role for this kinase in osteoclast fusion. These results validate our screening method as an efficient tool to identify novel fusion- regulating genes.