To date, numerous microRNAs (miRNAs) have been discovered. However, the function of these miRNAs is largely unknown. While our knowledge of miRNA post-transcriptional processing has greatly expanded in recent years, we have a limited understanding of the regulation and transcription of miRNA genes. In this Study, we characterized two BMP-2 upregulated miRNAs, miR-24-1 and miR-31, in mesenchymal stem cells and showed their opposing function in controlling cellular proliferation, and adipogenesis. Furthermore, we are the first to identify and characterize mouse intronic miR-23b similar to 27b similar to 24-1 and intergenic miR-31 genes. Moreover, we found that pri-miR-23b, pri-miR-27b, and pri-miR-24-1 are transcribed independently and their expression profiles are unique when cells are treated with BMP-2, even though they are located closely together. (C) 2009 Elsevier Inc. All rights reserved.