Poster abstracts

Poster number 10 submitted by Sankha Ghosh

Ectopic Expression of miR-146A in Myeloid Precursors Abrogates Osteoclast Differentiation

Sankha Ghosh (MCDB, MCB, CCC), Sudarshana M Sharma (MCB, CCC), Jamie Wolf (MG), Haritha Mathsyaraja (MCDB, MCB, CCC), Agnieszka Bronisz (MCB, CCC), Michael C Ostrowski (MCB, CCC)

Abstract:
MicroRNAs (miRNAs) are small non-coding RNAs that have the ability to either suppress translation or degrade target mRNA thereby modulating cellular events. Here we demonstrate an essential role of miRNAs in differentiation of osteoclasts, cells involved in bone remodeling. Two cytokines RANKL and CSF-1 induce differentiation of myeloid precursors to osteoclasts. Microarray analysis comparing myeloid precursors and differentiating osteoclasts for differentially expressed miRNAs, recognized miR146 as the only miRNA to get upregulated during osteoclast differentiation. Further analysis indicated this miRNA to be miR-146a, one of the two isoforms of miR146. In silico analysis indicated TRAF6 as a potential target of mir146a that was confirmed using in vitro experiments. Ectopic expression of pre-miR146a in myeloid precursors resulted in decreased TRAF6 protein levels thereby attenuating osteoclast differentiation. At the molecular level this resulted in reduced level of expression of osteoclast marker genes Cathepsin K and acid phosphatase 5. Co-transfection of TRAF6 with mutated 3'UTR or its downstream effector MKK6 with miRNA 146a alleviated the effect of miR146a and rescued the expression of osteoclast specific genes. Collectively our results show that mir-146a establishes a negative feed back loop regulating osteoclast differentiation and ectopic expression of miR146a in myeloid precursors has the ability to abrogate osteoclast lineage specification.

Keywords: Osteoclast, Differentiation, MicroRNA