Statement of Benefit to California:
SYNOPSIS: The proposal focuses on a much-neglected area of hES cell biology, the mitochondria. The aims are to (1) create hESC that contain mtDNA mutations that cause human disease and examine their growth and differentiation into neurons and (2) analyze the mtDNA mutations in various hESC lines and the effect of these mutations on growth and differentiation. SIGNIFICANCE AND INNOVATION: The innovation is high in this proposal, bringing experts in the mitochondrial medicine field into hES cell biology. The investigators choose to look at the mitochondrial genome in hES cells and assess its importance in pluripotency and differentiation, a subject that almost no one has had the foresight to examine. This will be an exhaustive look at mitochondrial function in hES cells, and hopefully this information will be used down the road to help increase the efficiency of cell cultivation techniques and the efficiency of some differentiation pathways. Unfortunately, as there is no strong evidence that mitochondrial mutations effect hES pluripotency the significance of the proposal is unclear, but potentially quite high. STRENGTHS: The strength of the proposal is the enormous expertise in mitochondrial medicine and biology brought to the table. The investigators and their collaborators are clearly among the world’s leaders in understanding mitochondrial function and its impact on cell biology. One reviewer stated this is hands down the most well written, well planned and well substantiated proposal they have the opportunity to evaluate - one word, excellent. WEAKNESSES: One weakness of the proposal is that there is no evidence that mutations in the mitochondrial genome exist in ES cells or that they will effect pluripotency, but that is all the more reason to do the experiments. Another weakness is that the description of neuronal differentiation, and particularly the analysis of neuronal differentiation, is left to the imagination. Presumably non-neuronal differentiation will be examined as well as looking for the efficiency of neuronal differentiation. In this regard, ‘differentiation’ is treated as a single entity in the grant, and it is likely based on the literature, that differentiation will be skewed (not just halted) by changes in mitochondrial function. Reviewers had three suggestions for the PI. First, the aims should be reversed in time. It would be good to know the mitochondrial history of the cells before they are used for the heteroplasmic ES cell substrates. Second, it is clear that hES cells generated by SCNT would display considerable mitochondrial heteroplasmy, which might effect their growth, viability, pluripotency, and utility for cell transplantation (i.e., rejection due to donor oocyte mitochondria). The investigators might mention this as a nice benefit of doing these types of experiments in their proposal. Third, the investigators might create a seemingly normal mitochodrial heteroplasmic hES cell and assess the consequences. DISCUSSION: This proposal was one of the best that was reviewed by the panel. The work may not be terribly sexy, but looking at the effects of mitochondrial mutations on growth and differentiation is incredibly innovative. The science is beautifully presented, and SCNT approach is "incredibly innovative", especially in studies with mitochondria and pluripotency. To make this totally great, the PI would only have to reverse the order of the Aims in time.