Department of Anatomy and Regenerative Biology
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Ali Ramezani, Ph.D.
Assistant Research Professor of Anatomy and Regenerative Biology
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Background
B.Sc. (1993) University of Toronto
Ph.D. (2002) University of Toronto
Postdoctoral Fellow (1999-2003) American Red Cross
Research Scientist (2003-2004) American Red Cross
Research Scientist (2004-2007) George Washington University
Research Interests
My major research interests are in the field of hematopoietic stem cell (HSC) gene therapy. Since HSC gene therapy applications require efficient gene delivery and expression, many of my past studies have involved enhancing gene expression from gammaretroviral and lentiviral vectors. My mentor, Dr. Robert Hawley, and I have developed several HIV-1-derived lentiviral vectors for gene delivery and expression in hematopoietic cells (1-3) and were amongst the first to include chromatin insulators and scaffold attachment regions in these vectors in order to minimize position effects and maintain high-level transgene expression (4).
Our group has also focused on improving gammaretroviral vector design. For these studies, we employed mouse embryonic stem cells (ESCs) stimulated to differentiate into hematopoietic cells in vitro. Although gammaretroviral vectors derived from Moloney murine leukemia virus are routinely used to introduce and express transgenes in hematopoietic cells, they are highly susceptible to transcriptional silencing in ESCs. Moreover, while some derivatives—such as MSCV—are transcriptionally active in undifferentiated ESCs, they still experience severe transcriptional down-regulation upon ESC differentiation. Following extensive testing of vector parameters, we created the MSinSB vector which directs stable transgene expression during in vitro hematopoietic development from ESCs (5).
Currently, we are developing an HSC-based gene therapy strategy for treatment of hemophilia A. Hemophilia A is an inherited bleeding disorder caused by deficiency of coagulation factor VIII (FVIII). There is no cure for hemophilia A and the main treatment is FVIII replacement therapy, which is expensive, inconvenient, and is only offered to 30% of hemophilia A patients worldwide. Furthermore, ~25-30% of patients with severe hemophilia A develop inhibitory antibodies to FVIII, prompting the need for immune tolerance induction in these patients. Hemophilia A is an excellent candidate for retroviral-mediated HSC gene therapy because modest elevation of FVIII levels to a few percent of normal is sufficient to significantly improve the clinical symptoms. However, the emergence of leukemia in HSC gene therapy patients with X-linked severe combined immunodeficiency disease due to retroviral vector insertional mutagenesis has prompted reevaluation of the safety profile of retroviral-mediated HSC gene delivery. Therefore, we have constructed new gammaretroviral and lentiviral vectors into which various safety features have been incorporated. In addition, we have generated a FVIII transgene (eFVIII) that encodes a more efficiently secreted FVIII protein that is less immunogenic. Finally, with a view toward clinical translation in the outpatient setting, we are evaluating nonmyeloablative conditioning regimens in a hemophilia A mouse model for durable engraftment of gene-modified HSCs with minimal treatment-associated toxicity.- Ramezani, A., Hawley, T.S., and Hawley, R.G. 2000. Lentiviral vectors for enhanced gene expression in human hematopoietic cells. Mol. Ther. 2, 458-469. PDF
- Ramezani, A., and Hawley, R.G. 2002. Overview of the HIV-1 lentiviral vector system. In: Current Protocols in Molecular Biology. (John Wiley & Sons, Inc.) 16.21.1-16.21.15. PDF
- Ramezani, A, and Hawley, R.G. 2002. Generation of HIV-1-based lentiviral vector particles. In: Current Protocols in Molecular Biology. (John Wiley & Sons, Inc.) 16.22.1-16.22.15. PDF
- Ramezani, A., Hawley, T.S., and Hawley, R.G. 2003. Performance- and safety-enhanced lentiviral vectors containing the human interferon-β scaffold attachment region and the chicken β-globin insulator. Blood 101, 4717-4724. PDF
- Ramezani, A., Hawley, T.S., and Hawley, R.G. 2006. Stable gammaretroviral vector expression during embryonic stem cell-derived in vitro hematopoietic development. Mol. Ther. 14, 245-254. PDF
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Last Updated: September 13, 2007
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