Fundamental mechanisms of microRNA regulation of gene expression and cell fate.
The overall mission of Dr. Charles E. Rogler's laboratory is to obtain a fundamental understanding of miRNA action as it pertains to aspects of liver development, growth and disease. In this quest we have focused on three major areas of research where new understanding is critically needed. These three areas are listed below.
1. Studies on the roles of miRNAs in hepatocarcinogenesis.
A major question remaining in cancer biology is understanding how oncogenes and tumor suppressor genes interact along common pathways involved in controlling malignant traits such as independence from growth factors, immortalization, avoiding apoptosis, angiogenesis, and metastatic capacity. miRNAs are a relatively new class of genes that impact on virtually all aspects of mammalian development and malignant conversion of cells.
Our laboratory has pioneered studies in which miRNAs have been shown to have oncogenic roles in hepatocarcinogenesis. After determining the miRNA profiles of Hepatocelllular Carcinoma's (HCC),( Pub #3) we identified a specific miRNA polycistron, designated the miR-17-92 locus, in which miRNA are up-regulated in virtually all primary HCCs. We also showed that knockdown of the miR 17-92 locus miRNAs partially reverses the malignant phenotype (Pub #5)
Recently we have shown that the oncogenic microRNA, miR-21, specifically targets a tumor suppressor, RHOB. We showed that blocking miR-21 reduces the metastatic properties of HCC (Pub # 9). Studies are ongoing to identify new targets of the oncogenic miRNAs in order to understand how oncogenic pathways may be linked through miRNAs and to uncover new pathways involved in hepatocarcinogenesis.
2. Studies on the roles of miRNAs in liver stem cell differentiation.
During chronic disease the liver often utilizes its stem cell compartment, in addition to hepatocyte regeneration, to restore liver mass. However, our understanding of mechanisms controlling differentiation of liver stem cells is fragmentary. microRNAs play important roles in cellular differentiation and provide an entirely new framework to understand molecular control of cellular differentiation.
Our laboratory has recently discovered that a a specific set of three miRNAs from the miR-23b polycistron, (namely miRs-23b,27b, and 24) regulate one of the most important signal transduction networks in mammalian biology, namely the TGFbeta signaling pathway (Pub #7). We reported that all three miRNAs listed above specifically target a critical set of genes in the pathway, namely Smads 3,4, and 5. Our laboratory is actively pursuing investigations to understand the specific mechanisms of the interactions and the wide ranging biological effects of the miRNA regulatory actions.
3. Development of a biochemically based protocol for the global identification of miRNAs and miRNA targets involved in liver stem cell biology and liver disease.
The field of miRNA biology is currently limited by our knowledge of authentic miRNA targets. Without such information our understanding of roles of miRNAs will remain fragmentary. Our laboratory has developed a novel and specific biochemically based protocol for the isolation and identification of miRNAs and their targets from liver (unpublished data, manuscript in preparation).
Using deep sequencing we have now identified thousands of miRNA targets. This approach has, for the first time directly shown the importance of miRNAs in targeting large non-coding RNAs in the cell, such as H19. The approach has also identified functionally related genes that are targeted by miRNAs from the miR-23b polycistron.
We are continuing to develop and test exciting new hypotheses on miRNA action in the liver based on the deep set of data we have obtained. This approach is confirming our overall model that miRNAs will be shown to have very wide ranging effects on liver cell biology and differentiation as research proceeds in the coming years.
Representative Recent Publications (for complete list refer to PubMed)
Sun D, Melegari M, Sridhar S, Rogler CE, Zhu L. Multi-miRNA hairpin method that improves gene knockdown efficiency and provides linked multi-gene knockdown. Biotechniques. 2006 Jul;41(1):59-63.
Zhou H, Rogler LE, Teperman L, Morgan G, Rogler CE. Identification of hepatocytic and bile ductular cell lineages and candidate stem cells in bipolar ductular reactions in cirrhotic human liver. Hepatology. 2007 Mar;45(3):716-24.
Landgraf P, Rusu M, Sheridan R, Sewer A, Iovino N, Aravin A, Pfeffer S, Rice A, Kamphorst AO, Landthaler M, et al. A mammalian microRNA expression atlas based on small RNA library sequencing. Cell. 2007 Jun 29;129(7):1401-14.
Rogler CE, Zhou HC, LeVoci L, Rogler LE. Clonal, cultured, murine fetal liver hepatoblasts maintain liver specification in chimeric mice. Hepatology. 2007 Dec;46(6):1971-8.
Connolly E, Melegari M, Landgraf P, Tchaikovskaya T, Tennant BC, Slagle BL, Rogler LE, Zavolan M, Tuschl T, Rogler CE. Elevated expression of the miR-17-92 polycistron and miR-21 in hepadnavirus-associated hepatocellular carcinoma contributes to the malignant phenotype. Am J Pathol. 2008 Sep;173(3):856-64.
Rogler CE. MicroRNAs make inroads into liver development. Gastroenterology. 2009 Mar;136(3):770-2.
Rogler CE, Levoci L, Ader T, Massimi A, Tchaikovskaya T, Norel R, Rogler LE. MicroRNA-23b cluster microRNAs regulate transforming growth factor-beta/bone morphogenetic protein signaling and liver stem cell differentiation by targeting Smads. Hepatology. 2009 Aug;50(2):575-84.
Rogler CE, Rogler LE. miRNAs and liver biology. In: The Liver: Biology and Pathobiology, Fifth Edition, eds, Arias IM, Alter HJ, Boyer JL, Cohen DE, Fausto N, Shafritz DA, Wolkoff AW. Wiley-Blackwell, Chapter 63, pp. 1029-1052, 2009.
Connolly EC, Van Doorslaer K, Rogler LE, Rogler CE. Overexpression of miR-21 promotes an in vitro metastatic phenotype by targeting the tumor suppressor RHOB. Mol Cancer Res. 2010 May;8(5):691-700.
Rogler LE, Kosmyna B, Moskowitz D, Bebawee R, Rahimzadeh J, Kutchko K, Laederach A, Notarangelo LD, Giliani S, Bouhassira E, Frenette P, Roy-Chowdhury J, Rogler CE. Small RNAs derived from lncRNA RNase MRP have gene-silencing activity relevant to human cartilage-hair hypoplasia. Hum Mol Genet. 2014 Jan 15;23(2):368-82. doi: 10.1093/hmg/ddt427. Epub 2013 Sep 5.
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