MicroRNA-214 suppresses osteogenic differentiation of C2C12 myoblast cells by targeting Osterix

Evolution of the miR199-214 cluster and vertebrate skeletal development

MicroRNA (miRs) are short non-coding RNAs that fine-tune the regulation of gene expression to coordinate a wide range of biological processes. MicroRNAs are transcribed from miR genes and primary miR transcripts are processed to approximately 22 nucleotide single strand mature forms that function as repressors of transcript translation when bound to the 3'UTR of protein coding transcripts in association with the RISC. Because of their role in the regulation of gene expression, miRs are essential players in development by acting on cell fate determination and progression toward cell differentiation. The miR199 and miR214 genes occupy an intronic cluster located on the opposite strand of the Dynamin3 gene. These miRNAs play major roles in a broad variety of developmental processes and diseases, including skeletal development and several types of cancer. In the work reported here, we first deciphered the origin of the miR199 and miR214 families by following evolution of miR paralogs and their host Dynamin paralogs. We then examined the expression patterns of miR199 and miR214 in developing zebrafish embryos and demonstrated their regulation through a common primary transcript. Results suggest an evolutionarily conserved regulation across vertebrate lineages. Our expression study showed predominant expression patterns for both miR in tissues surrounding developing craniofacial skeletal elements consistent with expression data in mouse and human, thus indicating a conserved role of miR199 and miR214 in vertebrate skeletogenesis.

miR-145 suppresses osteogenic differentiation by targeting Sp7

Osteogenesis depends on a coordinated network of transcription factors including Sp7. Emerging evidence indicates that microRNAs (miRNAs) act as pivotal regulators in various biological processes including osteoblast proliferation and differentiation. Here, we investigated the effect of miR-145 on osteogenic differentiation. miR-145 was decreased during osteogenic differentiation, which could suppress the osteogenic differentiation of C2C12 and MC3T3-E1 cells confirmed by gain- and loss-of-function experiments. Moreover, bioinformatic analysis combined with luciferase reporter assay, and Western blot validated that miR-145 negatively regulated Sp7 expression. Inhibition of Sp7 showed similar effect with miR-145 on osteogenic differentiation, whereas overexpression of Sp7 attenuated this effect. Collectively, these data indicate that miR-145 is a novel regulator of Sp7, and it suppresses the osteogenic differentiation of C2C12 and MC3T3-E1 cells.