Bio

Honors & Awards


  • CIRM Scholar, Stanford University

Professional Education


  • Ph.D, Cold Spring Harbor Laboratory & Stony Brook University, Genetics (2009)
  • B.S., Stony Brook University, Biochemistry (2002)

Stanford Advisors


Research & Scholarship

Current Research and Scholarly Interests


My research focuses on microRNAs, stem cells and immune clearance

Publications

Journal Articles


  • A role for microRNAs in maintenance of mouse mammary epithelial progenitor cells GENES & DEVELOPMENT Ibarra, I., Erlich, Y., Muthuswamy, S. K., Sachidanandam, R., Hannon, G. J. 2007; 21 (24): 3238-3243

    Abstract

    microRNA (miRNA) expression profiles are often characteristic of specific cell types. The mouse mammary epithelial cell line, Comma-Dbeta, contains a population of self-renewing progenitor cells that can reconstitute the mammary gland. We purified this population and determined its miRNA signature. Several microRNAs, including miR-205 and miR-22, are highly expressed in mammary progenitor cells, while others, including let-7 and miR-93, are depleted. Let-7 sensors can be used to prospectively enrich self-renewing populations, and enforced let-7 expression induces loss of self-renewing cells from mixed cultures.

    View details for DOI 10.1101/gad.1616307

    View details for Web of Science ID 000251627200004

    View details for PubMedID 18079172

  • MicroRNA93 Regulates Proliferation and Differentiation of Normal and Malignant Breast Stem Cells PLOS GENETICS Liu, S., Patel, S. H., Ginestier, C., Ibarra, I., Martin-Trevino, R., Bai, S., McDermott, S. P., Shang, L., Ke, J., Ou, S. J., Heath, A., Zhang, K. J., Korkaya, H., Clouthier, S. G., Charafe-Jauffret, E., Birnbaum, D., Hannon, G. J., Wicha, M. S. 2012; 8 (6)

    Abstract

    MicroRNAs (miRNAs) play important roles in normal cellular differentiation and oncogenesis. microRNA93 (mir-93), a member of the mir106b-25 cluster, located in intron 13 of the MCM7 gene, although frequently overexpressed in human malignancies may also function as a tumor suppressor gene. Using a series of breast cancer cell lines representing different stages of differentiation and mouse xenograft models, we demonstrate that mir-93 modulates the fate of breast cancer stem cells (BCSCs) by regulating their proliferation and differentiation states. In "claudin(low)" SUM159 cells, expression of mir-93 induces Mesenchymal-Epithelial Transition (MET) associated with downregulation of TGFβ signaling and downregulates multiple stem cell regulatory genes, including JAK1, STAT3, AKT3, SOX4, EZH1, and HMGA2, resulting in cancer stem cell (CSC) depletion. Enforced expression of mir-93 completely blocks tumor development in mammary fat pads and development of metastases following intracardiac injection in mouse xenografts. The effect of mir-93 on the CSC population is dependent on the cellular differentiation state, with mir-93 expression increasing the CSC population in MCF7 cells that display a more differentiated "luminal" phenotype. mir-93 also regulates the proliferation and differentiation of normal breast stem cells isolated from reduction mammoplasties. These studies demonstrate that miRNAs can regulate the states and fates of normal and malignant mammary stem cells, findings which have important biological and clinical implications.

    View details for DOI 10.1371/journal.pgen.1002751

    View details for Web of Science ID 000305961000018

    View details for PubMedID 22685420

  • Probing tumor phenotypes using stable and regulated synthetic microRNA precursors NATURE GENETICS Dickins, R. A., Hemann, M. T., Zilfou, J. T., Simpson, D. R., Ibarra, I., Hannon, G. J., Lowe, S. W. 2005; 37 (11): 1289-1295

    Abstract

    RNA interference is a powerful method for suppressing gene expression in mammalian cells. Stable knock-down can be achieved by continuous expression of synthetic short hairpin RNAs, typically from RNA polymerase III promoters. But primary microRNA transcripts, which are endogenous triggers of RNA interference, are normally synthesized by RNA polymerase II. Here we show that RNA polymerase II promoters expressing rationally designed primary microRNA-based short hairpin RNAs produce potent, stable and regulatable gene knock-down in cultured cells and in animals, even when present at a single copy in the genome. Most notably, by tightly regulating Trp53 knock-down using tetracycline-based systems, we show that cultured mouse fibroblasts can be switched between proliferative and senescent states and that tumors induced by Trp53 suppression and cooperating oncogenes regress upon re-expression of Trp53. In practice, this primary microRNA-based short hairpin RNA vector system is markedly similar to cDNA overexpression systems and is a powerful tool for studying gene function in cells and animals.

    View details for DOI 10.1038/ng1651

    View details for Web of Science ID 000233045200032

    View details for PubMedID 16200064

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