Basic Biology IV
Mitochondria in our cells provide majority of cellular energy. Neuron and cardiomyocyte are sensitive to mitochondria failure due to their great energy demand. Mitochondria have their own DNA (mtDNA) to code for proteins essential for energy production, and each cell has several hundred copies of mtDNA subject to damage as we age. mtDNA mutations are implicated in common diseases, such as Parkinson’s disease, diabetes and autism. mtDNA mutation can be inherited from mother to offspring which can cause severe childhood neurological disorders. The therapeutic options are extremely limited because of poor understanding on mtDNA diseases. We can change the nuclear DNA but we don’t have similar technology with mtDNA. Therefore, the recent developed reprogramming technology that allows derivation of human induced pluripotent stem cells (hiPSC) from patients, which can then be differentiated into disease-specific neurons, can be the long-sought solution for mtDNA disease studies. In this proposal, we will derive hiPSC from mtDNA patients with Maternal Inherited Leigh’s Syndrome (MILS) and differentiate them into neurons, which will be analyzed with a series of functional and molecular tests to find out the reasons of patient neuron death and the potential rescue mechanism. We believe the findings made will have a significant clinical and scientific impact on understanding the molecular and pathological mechanism of mtDNA disease and drug screen.
Statement of Benefit to California:
Maternal Inherited Leigh’s Syndrome (MILS) is the most common hereditary mitochondria DNA disease that causes severe childhood neurological disorders. In this study, we will generate hiPSC-derived neurons from patients with MILS, and then perform a series of functional and molecular analyses to determine the reason underlying the neuron cell death observed in MILS children. We believe patient neuron generated through iPSC technology will greatly advance the ability to perform future drug discovery and therapy evaluation as we will attempt in the study. It is estimated that 1 in 2000 individuals is affected by mitochondrial diseases; however, the exact prevalence of mitochondria DNA disease is hard to estimate due to the challenges of quantifying the mutations. In a recent clinical report in the Journal of American Medical Association, 2/10 autistic children were found to have mtDNA deletions and 5/10 had mtDNA replication defects, and moreover, widespread mtDNA heterogeneity has recently been found in normal human cells. Thus, mtDNA mutation is not as rare as believed, and its role in disease is underappreciated. MILS disease on its own is a rare disease, but it presents a severe form of general mitochondria dysfunction underling a much broader range of mtDNA diseases. Therefore, we believe that therapies resulting from these research findings will benefit the state of California and its citizens.
The goal of the research described in this proposal is to develop a disease-in-a-dish model for an inherited mitochondrial disease, Maternal Inherited Leighís Syndrome (MILS). MILS causes severe neurological defects in children, and this and similar mitochondrial disorders affect 1 in 2000 individuals. The first specific aim will be to generate additional induced pluripotent stem cell (iPSC) lines and appropriate control cell lines from MILS patients. The second aim is to characterize the bioenergetics profiles of neurons undergoing differentiation from progenitors carrying MILS-mutant mitochondria. The third specific aim will be to test potential therapeutic agents and develop new approaches for drug discovery using iPSC-derived MILS neurons. Significance and Innovation - Reviewers found the proposed study particularly significant, since there are currently no effective therapies and very few experimental models for mitochondrial diseases. - Proposed experiments should provide greater understanding of the basic pathogenesis of MILS disease. - If successful, the project could lead to the identification and in vitro testing of novel therapeutic agents. Feasibility and Experimental Design - Overall, the project featured well-reasoned strategies, methods and generally feasible approaches. - Although the application included a substantial amount of preliminary data relating to aims 1 and 2, critical results demonstrating bioenergetic differences between controls and neuronal cultures from MILS patients were absent. - Potential problems due to heterogeneity in cell proliferation and the possibility that different mutations may affect cellular differentiation potential were not adequately addressed. - Reviewers expressed concern that aim 3 was significantly underdeveloped and not supported by preliminary studies. Principal Investigator (PI) and Research Team - PI is an outstanding scientist, extremely prolific researcher and leader in the study of signal transduction pathways that regulate the cell cycle. - Reviewers expressed some concerns that the PI and research team has limited expertise in research on either mitochondria or stem cells. - Composition of the research team appears generally adequate to carry out the proposed studies. - An exceptional group of collaborators are associated with the project; however they are not directly involved as key personnel, and their level of commitment is unclear. Responsiveness to the RFA - The proposal is entirely responsive to the RFA
- This application scored below the initial scientific merit funding line, no programmatic reason to fund the application was proposed, and the GWG voted to place the application in Tier 3, Not Recommended for Funding.
- Jane Johnson