The goal of this project is to use patient-specific induced pluripotent stem cells (iPSCs) as a platform for the development of novel therapies for patients suffering with dyskeratosis congenita (DC), a bone-marrow failure syndrome that presents with poor life expectancy and multi-systemic tissue defects that include aplastic anemia and pulmonary fibrosis. A combination of technologies will be used to achieve this goal, including genetic correction, high-throughput sequencing, small-molecule drug screening and targeted differentiation of DC iPS cells to hematopoietic fates. All patients with DC have very short telomeres for their age, typically below the first percentile length when compared to the rest of the population. All mutations discovered in DC so far were in genes related to telomere homeostasis, either in telomerase, or directly binding to telomeres. Telomerase is the multi-enzymatic complex responsible for telomere synthesis in mammalian cells. In the absence of telomerase, telomeres will progressively shorten, which has been linked to impaired stem cell function in mice and humans. Thus, the tissue defects observed in DC likely result from the loss of self-renewal in adult stem cells compartments of these patients, caused by accelerated telomere shortening in settings of mutant telomerase. The central hypothesis of this project is that disease-specific iPS cells offer a novel and suitable system to study the consequences of mutant telomerase and the loss of self-renewal in DC pluripotent cells and can be used to search for strategies to correct this phenotype. I have previously shown that iPS cells derived from patients showing variable severity of DC faithfully recapitulate the telomere shortening and loss of self-renewal phenotypes observed in human patients. Here, I propose to use these patient-specific iPS cells to understand in detail the loss of self-renewal phenotype arising from dysfunctional telomeres and to use these cells as a platform for drug discovery and targeted differentiation, which could enable novel protocols for clinical therapy in the future.
The Specific Aims are (I) to reverse the self-renewal defect in DC patient-specific iPS cells by genetic complementation and high- throughput gene expression analysis of DC iPS cells with critically short telomeres and (II) to use DC iPS cells as a platform for developing new therapies against DC, by searching for telomerase stabilizing drugs and by specifically differentiating these cells into hematopoietic fates. This project will significantly increase the current knowledge on bone-marrow failure syndromes, by first understanding the deleterious effects of dysfunctional telomeres in human pluripotent cells, and then by devising novel strategies to treat patients afflicted with dyskeratosis congenita, a disease that currently has no cure.
The discovery of methods that allow the conversion of adult somatic cells into induced pluripotent stem cells (iPSCs) has raised the unprecedented possibility of producing custom-tailored cells for the study and treatment of several inherited and acquired diseases. In this proposal, we will use disease-specific iPS cells that we have recently derived from patients afflicted with the bone marrow failure syndrome dyskeratosis congenita, as a platform for the development of future clinical therapies against this disease. Using a combination of different genetic and biochemical tools, the experiments proposed will greatly increase our knowledge on stem cell function and regulation in bone marrow failure syndromes.
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| Fok, Wilson Chun; Niero, Evandro Luis de Oliveira; Dege, Carissa et al. (2017) p53 Mediates Failure of Human Definitive Hematopoiesis in Dyskeratosis Congenita. Stem Cell Reports 9:409-418 |
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