New Faculty I
$2 229 427
Statement of Benefit to California:
SYNOPSIS: There are currently two possible approaches toward the generation of patient-specific embryonic stem cells. One involves nuclear transfer and cloning (SCNT), and the other involves reprogramming of an adult differentiated state. SCNT is very inefficient and suffers from very limited source of donated biological material. Reprogramming of somatic cells into embryonic stem cells (ESC) has recently been shown to be possible in mouse cells by the Yamanaka group as well as the Jaenisch group. Both groups have reported that overexpression of 4 transcription factors (Oct4, Sox2, c-Myc, and Klf4) can convert murine fibroblasts to ESC-like cells (induced pluripotent cells, iPS cells). The overall goal of the proposal is to understand the molecular mechanisms underlying somatic cell reprogramming to an embryonic state in mice, to improve reprogramming protocols, to apply this knowledge to the reprogramming of human somatic cells, and examine chromatin and transcription factor targets and changes during the reprogramming process. The PI has recently published a paper with a former colleague (K. Hochedlinger), comfirming the Yamanaka data and showing that selection by inspection for ESC-like morphology is sufficient to isolate iPS cells with an improved phenotype. In that study she performed the chromatin experiments showing that the chromatin of iPS cells is virtually indistinguishable from that of ESC. STRENGTHS AND WEAKNESSES OF THE RESEARCH PLAN: Understanding the reprogramming process is highly important within the stem cell field. If reprogramming could be improved and applied to human cells, it might revolutionize approaches to the creation of disease- and individual-specific ES cells and will inevitably move the field closer to clinical applications. While this work is on the forefront of stem cell biology, and the PI is experienced and successful, leaving little doubt that interesting results will be obtained, the actual methods and approaches proposed in this application are not particularly innovative. There are assuredly many laboratories engaged in similar types of experiments attempting to adapt the Yamanaka approach to human cells. The proposed experiments are feasible and the PI has the requisite background to address the aims. In Aim 1, several different approaches are proposed for introducing the transcription factors into cells (adenovirus, retrovirus, inducible versions, reprogrammable mice, and the introduction of additional factors). These are all defensible but the possibilities are laid out without much prioritization as to the order and weight to be applied to each. The second aim is by far the most significant one, as one can argue that regardless of the mechanism of reprogramming that the PI proposes to dissect in the mouse in Aim 1, ultimately it is the human reprogramming experiment that would be relevant. One reviewer therefore strongly suggested the prioritization of the second aim. There is no doubt in the mind of the PI and the rest of us that many human ESC groups are focused to address this issue, so far without any success, since the same strategy that was successful in the mouse does not seem to work in humans. The PI should expect tremendous scrutiny in this area from other investigators. If maximium effort is not dedicated to this aim the goal might not be achieved, and she will be scooped. In Aim 3, the PI goes back to the mouse to address the mechanism of reprogramming. There is some naivete in scientific assumptions within this aim that might or might not turn out to be valid. For example, the PI states with confidence that: “The central issue of reprogramming is clearly an epigenetic one: how is the donor genome reprogrammed to ensure correct activation of those genes needed for embryonic development and inactivation of those that are donor cell-specific . Therefore the question becomes: how do the four transcription factors induce global epigenetic remodeling of the genome?” Epigenetic influences represent only one aspect of reprogramming. Most importantly, though, the reviewers emphasized that the proposed studies on reprogramming are highly significant in that they have the potential to move the stem cell field significantly closer toward clinical applications. QUALIFICATIONS AND POTENTIAL OF THE PRINCIPAL INVESTIGATOR: Dr. Plath is a talented investigator with many important contributions to her field, as shown by her excellent list of publications. The PI has superb training in cell biology, chromatin biology, and ESC, and she has recently contributed her chromatin expertise to a paper on somatic reprogramming. She has also been highly successful in grant applications as she is a Kimmel Scholar and was awarded an NIH New Innovator Award. A strong body of her prior work relates to the mechanisms of X chromosome inactivation. There is no hesitation affirming that she and her team are perfectly qualified to perform all the specific aims of this grant.The PI’s career plan is excellent, she has a clear view of how she would like to advance academically and in her research. INSTITUTIONAL COMMITMENT TO PRINCIPAL INVESTIGATOR: UCLA is the best institution for these studies, encompassing all of the necessary resources and centers to successfully execute the proposed specific aims. The institutional commitment to the PI is outstanding, she was recruited with a strong package and has the backing of her department and the institution. The presence of a stem cell program at UCLA is an asset. DISCUSSION: Overall, the panel expressed tremendous enthusiasm about this proposal, because of its potential impact on the stem cell field. The proposed research on reprogramming of adult human somatic cells toward an ESC-like state is of highest priority in the field, potentially paving the way for the derivation of patient-specific cell lines. Moreover, the candidate is very talented, has an excellent track record, and she is well-positioned with all the right tools in place to address reprogramming in human cells. In short, the reviewers expressed confidence that the proposed work would get done. Clearly, this field of highest scientific priority is highly competitive, which prompted some discussion about wheher this candidate could be “first” to complete the work. But, with the right funding, this PI could be the right person to develop this methodology. Therefore, the panel agreed that the work on the human cells should be prioritized. In addition to the work on human cells, the PI proposes detailed studies on mouse cells. The science was considered very good. However, the question was raised if the mouse work would yield data relevant to the human case, since data are emerging in the field suggesting that there are many differences in reprogramming between mouse and human cells.