Stem Cell Center, Yale: Stem Cell Genetics | Stem Cell Self-Renewal and Cell Symmetry
Our long-term research interest is to understand how cell-fate decisions in stem cells are regulated at the molecular level. Our immediate focus is to define how the numerous components and pathways function coordinately to regulate self-renewal and commitment to differentiation in embryonic and hematopoietic stem cells, the two stem cell systems the lab is currently focusing on. For these studies we employ a broad-based strategy that integrates molecular, cellular and organismal approaches. The overall goal is to gain a comprehensive and deep understanding of fundamental cell fate choices.
Extensive Research Description
Embryonic and adult stem cells hold great promise for regenerative
medicine, tissue repair and gene therapy. Embryonic stem cells
represent a transient cell population that exist during embryonic
development and can give rise to all cell types present in an adult,
while adult (somatic) stem cells are permanent cell populations
dedicated to homeostatic production of mature cells in tissues such as
blood, skin and gut. All stem cells must be able to balance
self-renewal versus differentiation, regulate proliferation and cell
death. Our long-term goal is to understand how cell-fate decisions in
stem cells are regulated at the molecular level. We have recently
developed a functional genomics approach to identify genetic mechanisms
that control self-renewal in mouse embryonic stem cells.
This approach utilizes short hairpin RNA (shRNA) loss-of-function techniques to downregulate a set of gene products whose expression patterns suggest self-renewal regulatory functions. We have applied this approach to a selected panel of candidate regulators and demonstrated that in addition to previously identified Nanog, Oct4 and Sox2 several other genes are required for efficient self-renewal of ES cells in vitro (Ivanova et al., Nature 2006). We are currently extending this screening strategy to genome-scale shRNA libraries.
Embryonic stem cells:
We have recently developed a functional genomics approach to identify genetic mechanisms that control self-renewal in embryonic stem cells. This approach utilizes short hairpin RNA (shRNA) loss-of-function techniques to downregulate a set of gene products whose expression patterns suggest self-renewal regulatory functions. We have applied this approach to a selected panel of candidate regulators and demonstrated that in addition to previously identified Nanog, Oct4 and Sox2 several other genes are required for efficient self-renewal of ES cells in vitro (Ivanova et al., Nature 2006). We are currently extending this screening strategy to genome-scale shRNA libraries.
Hematopoietic stem cells:
Hematopoiesis is organized as a hierarchy of cells of with decreasing self-renewal and differentiation potential. Long-term HSC, the most primitive cell in this hierarchy, can give rise to all blood lineages and has unlimited capacity to self-renew. LT-HSC produces short-term HSC which are still multipotent but are limited in self-renewal capacity. ST-HSC differentiates further into lineage-committed progenitor cells which are responsible for the large-scale production of mature blood cells. We have chosen global gene expression analysis in primary cells followed by functional characterization of candidate gene products as an approach towards the comprehensive identification of HSC regulatory mechanisms. To date we have performed transcriptional profiling of fetal and adult HSC using microarray-based technologies and have defined sets of genes that are specifically expressed in HSC but not in more differentiated compartments of the hematopoietic hierarchy(Ivanova, Science 2002). We currently study several candidate genes that are likely to function as key regulators of self-renewal and differentiation.
- Large-scale loss-of-function analyses to identify gene products that are required for self-renewal of mouse and human ES cells, and for commitment to specific lineages.
- In-depth characterization of previously identified regulators of self-renewal and differentiation.
- Computational modeling of lineage commitment.
- Single-cell gene expression analysis to define functional subsets within HSC.
- Functional analyses of candidate genes to identify gene-products that are necessary and/or sufficient for self-renewal of HSC both in vivo and in vitro.
- Oron E, Ivanova N*. Cell fate regulation in early mammalian development. Phys Biol. 2012 Aug;9(4):045002.
- Kloc A, Ivanova N*. Chromatin and Pluripotency: the MYSTerious Connection. Cell Stem Cell. 2012 Aug 3;11(2):139-40.
- Wang Z, Oron E, Nelson B, Razis S, Ivanova N*. Distinct lineage specification roles for NANOG, OCT4, and SOX2 in human embryonic stem cells. Cell Stem Cell. 2012 Apr 6;10(4):440-54.
- Fasano C, Dimos J, Ivanova N, Lowry N, Lemischka I, Temple S. shRNA Knockdown of Bmi-1 Reveals a Critical Role for p21-Rb Pathway in NSC Self-Renewal during Development. Cell Stem Cell 2007 1: 87-99.
- Ivanova N*, Dobrin R, Lu R, Kotenko I, Levorse J, DeCoste C, Schafer X, Lun Y, Lemischka IR*. Dissecting self-renewal in stem cells with RNA interference. Nature. 2006 Aug 3; 442: 533-8.
- Shen Q, Wang Y, Dimos JT, Fasano CA, Phoenix TN, Lemischka IR, Ivanova N, Stifani S, Morrisey EE, Temple S. The timing of cortical neurogenesis is encoded within lineages of individual progenitor cells. Nat Neurosci. 2006 Jun; 9(6):743-51.
- Ivanova N, Dimos J, Schaniel C, Hackney J, Moore K, Lemischka I. A Stem Cell Molecular Signature. Science 2002 298: 601-604
- Phillips R, Ernst R, Brunk B, Ivanova N, Moore K, Overton G and Lemischka I. The Genetic Program of Hematopoietic Stem Cells. Science. 2000 Jun 2;288(5471):1635-40.
- Ivanova N and Belyavsky A. Identification of differentially expressed genes by restriction endonuclease-based gene expression fingerprinting., Nucleic Acids Res. 1995, v. 23, p. 2954-2958