Welcome to the microRNA world!

About miRNAs

MicroRNAs (miRNAs) are 20-22 nucleotide small, RNA molecules encoded in the genomes of plants and animals that are known to regulate the expression of genes by binding (generally) to the 3'-untranslated regions (3'-UTR) of target mRNAs.

Although the first published description of miRNAs appeared in 1993 (Lee et al 1993), it has only been in the last 6-7 years that the breadth and diversity of this class of small, regulatory RNAs been appreciated. A great deal of effort has gone into understanding how, when, and where miRNAs are produced and function in cells, tissues, and organisms. Each microRNA may regulate multiple genes (often dozens) and since hundreds of miRNA genes are predicted to be present in higher eukaryotes (Lim 2003) the potential regulatory circuitry afforded by microRNA is enormous. Several research groups have provided evidence that miRNAs may act as key regulators of processes as diverse as early development (Reinhart 2000), cell proliferation and cell death (Brennecke 2003), apoptosis and fat metabolism (Xu 2003), and cell differentiation (Dostie 2003, Chen 2003).

Recent studies of miRNA expression implicate miRNAs in brain development (Krichevsky 2003), chronic lymphocytic leukemia (Calin 2004), colonic adenocarcinoma (Michael 2003), Burkitt’s Lymphoma (Metzler 2004), and viral infection (Pfeffer 2004) suggesting possible links between miRNAs and viral disease, neurodevelopment, and cancer. There is speculation that in higher eukaryotes, the role of miRNAs in regulating gene expression could be as important as that of transcription factors.

The interest of the Hardikar Laboratory in miRNAs has been since beginning of 2006. We are interested in looking at the role of different miRNAs in post-transcriptional gene regulation during pancreas development and regeneration. Studies carried out in our lab and several other laboratories worldwide demonstrate that miRNAs are involved in determination of cell fate during pancreas development. Using Taqman based assays from Applied Biosystems (AB), we have assessed miRNA profiles from several tissues during mouse embryonic development. Identification of specific miRNAs during pancreatic islet development would help us in understanding the miRNAs that may be involved in differentiation of endocrine pancreatic progenitor cells. We use miRNA real time pcr assays (human, mouse and rat) from Applied Biosystems, Foster City, CA. The laboratory also has a library of anti-miRNAs, expression vectors and luciferase based reporter systems to understand and validate the function of individual miRNA.