Mitochondria are known as the powerhouse of cells, generating energy (ATP) to power the biochemical processes of life. What is less well appreciated is that small organic molecules generated within mitochondria, called metabolites, traffic into the cell cytoplasm and nucleus where they act as essential cofactors for enzymes that regulate cell function. Leading cancer researchers worldwide now recognize how important changes in metabolites are for causing changes in the activities of enzymes that control gene expression, leading to cancer. Because cancers are biochemically abnormal, questions about how metabolites control cell differentiation cannot be easily addressed in the setting of cancer. It turns out that the ideal experimental system for this question is human pluripotent stem cells (hPSCs) and their differentiation into mature cell lineages. With two prior rounds of funding from CIRM, we determined that a metabolism gene, UCP2, regulates hPSC differentiation without knowing the mechanism. Since UCP2 regulates the manufacture of metabolites in mitochondria, we suspect this is a fundamental, key mechanism for regulating hPSC differentiation. Given our past productivity and success in this general area with 18+ publications using CIRM funds, we are uniquely positioned to determine how metabolism directly controls the genes that regulate hPSC self-renewal and differentiation potential, which has important implications for the field of regenerative medicine going forward.
Statement of Benefit to California:
Our proposal benefits California by adding new essential knowledge on metabolic mechanisms that control human pluripotent stem cell (hPSC) fate and function to support the taxpayers' commitment to personalized cell therapies. This work builds on highly successful 2-year CIRM Seed and 3-year Basic Biology I awards. CIRM funds to date resulted in 18+ published studies, numerous conference presentations, and the training of 14 individuals including post-docs, graduate students, undergraduates, and CIRM Bridges to Stem Cell Biology program trainees, some of whom have now entered the California workforce. Those studies provided the first methods and thorough characterizations of the function of mitochondria in stem and differentiated cells. This new CIRM BBIV proposal is groundbreaking for revealing how metabolism regulates changes in gene expression to drive hPSC differentiation, which has implications for regenerative medicine. Our ongoing work underpins therapy development in California’s major academic centers and will provide data for many of California's biotechnology and pharmaceutical companies in the ever growing stem cell industry, whose success will propel hiring and increased economic prosperity for the state. With success, tangible health and economic impact on California, its academic institutions and companies, and the rest of the nation will be achieved as California and its people lead the way forward with personalized medicine for the 21st century and beyond.
The project is concerned with understanding the role of mitochondria, the organelles of cellular energy metabolism, and particularly, mitochondrial metabolites, in regulating of human pluripotent stem cell (hPSC) self-renewal and differentiation. The first specific aim will be to alter key mitochondrial metabolism genes and evaluate the resultant metabolite changes in hPSCs. The second specific aim is to identify metabolite-regulated target genes and examine their control over hPSC self-renewal and differentiation.
Significance and Innovation
- Reviewers recognized that mitochondria provide critical function in stem cells and appreciated the broad significance of the proposed study.
- Reviewers were not convinced that the proposed research would address a major unsolved problem in the field.
- The project’s innovation is its focus on a poorly studied and novel aspect of stem cell biology.
Feasibility and Experimental Design
- Reviewers expressed strong concerns about the experimental approach and project’s feasibility.
- Methods proposed for altering metabolite levels were viewed as indirect, lacking specificity, and likely to have multiple cellular effects, some of which may be off-target.
- Reviewers questioned whether the experimental assumptions based on previous studies of metabolites in cancer cells would translate to studies of stem cells.
- The rationale for carrying out studies with both embryonic stem cells and induced pluripotent stem cell was unclear.
- Some reviewers felt that the preliminary data was supportive of the proposal, while others found that it did not adequately support the proposed study.
- It was unclear how alterations in pluripotency or differentiation potential would be quantified or shown to be a direct consequence of changes in cellular cofactor levels.
Principal Investigator (PI) and Research Team
- The PI is an outstanding investigator, with an excellent record of productivity.
- The PI and research team have appropriate qualifications and expertise to carryout the investigation.
Responsiveness to the RFA
- The proposed research was viewed as responsive to the RFA.