The development of methods to “reprogram” adult cells such as skin cells by simultaneously expressing four specific factors — Oct3/4, Sox2, c-Myc and Klf4 — in order to create cells resembling embryonic stem (ES) cells is a major breakthrough in stem cell biology. Our ability to generate these cells, which are known as induced pluripotent stem (iPS) cells, will allow us to obtain stem cells capable of maturing into any tissue type, which is critical for research and has great therapeutic potential, without the controversial use of embryos. We envision that human iPS cells generated from a patient could be used to generate specific cells or tissues for cell replacement therapies for that individual patient, without stimulating an adverse immune response. Certain disease-specific iPS cells could also be differentiated into diseased tissues to study the causes of those diseases or to screen for drugs to treat them. Differentiated cells from iPS cells could also be used for toxicology tests before a drug is given to patients. Therefore, iPS cell technology may make individualized medicine a reality in the future. However, molecular changes that underlie reprogramming of body cells are not yet well understood and must be defined before iPS cells can be safely used for patient-specific therapy.
In this study we will undertake biochemical and molecular analysis to try to understand cellular changes mediating reprogramming. These studies should help us to develop novel strategies to make reprogramming more efficient so that iPS cells can be generated on a large scale for use in regenerative medicine, individualized medicine and drug discovery.
California is the most populated state in the US. Many diseases and injuries suffered by the citizens of California, such as Alzheimer’s and Parkinson’s diseases, amyotrophic lateral sclerosis, multiple sclerosis, diabetes and cancer, could be treated using stem cells. The recent development of technology to transform skin cells into induced pluripotent stem (iPS) cells moves us one step closer to developing stem cells suitable for use as therapeutics. Stem cells generated from a patient could potentially be used to replace that individual’s diseased or damaged tissues without concern about an immune response. Disease-specific iPS cells may also be used for drug discovery and toxicology studies. Defining mechanisms underlying iPS cell induction is important before iPS cells can be used for therapy to treat degenerative disease and injuries. This application aims to study molecular mechanisms of iPS cell induction. The knowledge gained from this study can help us improve the efficiency of iPS cell induction. Our findings could also be commercialized by California-based biotechnology companies to generate revenue and create new job opportunities, while at the same time addressing some of the most devastating healthcare issues in our state.
This proposal explores the molecular mechanism by which the transcriptional regulators Klf4, Oct4 and Sox2 coordinate their activities to mediate reprogramming of human somatic cells to pluripotency. Aim 1 focuses on the role of physical interactions between these proteins in regulating gene expression and in the generation of induced pluripotent stem (iPS) cells, whereas Aim 2 addresses the role of a specific signal transduction pathway in Klf4/Oct4/Sox2-mediated reprogramming. Based on preliminary findings by the principal investigator (PI), the third aim will test the hypothesis that a transcription factor that has not yet been linked to the pluripotency factor network inhibits Klf4/Oct4/Sox2-mediated pluripotency gene expression and reprogramming in differentiated cells.
Overall, reviewers felt that this proposal has great potential to provide new mechanistic insights into the generation of iPS cells, and thus may provide important information for developing more efficient reprogramming strategies required for large scale production of iPS cells. Although standard techniques will be used to interrogate the molecular biology of the pluripotency-inducing transcription factors, reviewers felt that the specific molecular connections pursued in this proposal were innovative. The reviewers also appreciated that this is a clearly written, hypothesis-driven application. They differed in their assessment of the overall structure of the proposed aims, as some felt that the aims were disconnected, whereas others considered the presentation of three independent aims, each supported by excellent and extensive preliminary data, a strength. Feasibility was further supported by the proposed use of a secondary reprogramming assay with its improved reprogramming efficiency and greater homogeneity of iPS cell preparations when compared to standard methods. This assay has already been established in the PI's lab and will greatly facilitate the molecular analyses described in the proposal. A minor concern was raised regarding the feasibility of the proposed generation of dominant negative reagents for Aim 1, but reviewers concluded this was worth pursuing.
The PI is an outstanding young scientist with an excellent publication record and exceptional training. S/he has recruited appropriate experts in human pluripotent stem cell biology, molecular biology and bioinformatics as consultants to the project, and has already recruited two well trained postdoctoral scientists. Thus, the research team clearly has the expertise necessary to accomplish the proposal. The research environment is outstanding as well.
In summary, the reviewers expressed strong enthusiasm for this proposal based on its well-focused, sophisticated approach and its potential to provide a better understanding of how reprogramming proceeds and may be regulated. Confidence in the feasibility of this project was supported by strong preliminary data and the excellent qualifications of the PI and the assembled team.