This proposal is submitted in response to the RFA, RFA-OD-09-003, NIH Challenge Grants in Health and Science Research. The Broad Challenge Area is """"""""Stem Cells"""""""", and the specific Challenge is 14-HD-102: Identifying Reprogramming Factors for Oocytes. The advent of new stem cell approaches to cure disease and repair tissue damage is one of the most exciting developments in recent science. Some of the most exciting stem cell technology rests with the ability to reprogram nuclei. The oocyte is uniquely able to reprogram somatic cell nuclei to an embryonic, totipotent state, albeit with a low percentage of success in supporting term development. This power may be harnessed to derive stem cells. A key goal in pursuit of these exciting possibilities is to discover the specific oocyte factors that drive nuclear reprogramming, so that the reprogramming capacity of the oocyte can be manipulated to improve cloning, and so that those same factors can be exploited to advance stem cell technologies. However, there may be hundreds of factors in the oocyte that affect chromatin structure and gene transcription, but only a few of these may be relevant to reprogramming. Thus, simply cataloguing potential reprogramming factors that are expressed in an oocyte is of limited value. A clear relationship of expressed genes to reprogramming capacity of a cell is needed. Genetic systems that can correlate variations in a trait with a combination of gene mapping data and array expression differences offer unparalleled opportunity for circumventing such restrictions. The gene mapping data can greatly facilitate the interpretation of array data, and correlating array data with different variants in phenotype is likewise highly informative. We have available a genetic system that is ideal for this purpose. We have shown that clones made with C57BL/6 (B6) eggs progress beyond the 2-cell stage much more efficiently than those made with D2 eggs;F1 hybrid eggs support a higher still rate of development indicative of a hybrid vigor effect. Ability to direct cloned embryo development beyond the 2-cell stage is a clear indicator of oocyte reprogramming potential. Thus, D2 oocytes are inferior at reprogramming somatic cell nuclei to support early embryogenesis compared to B6 and F1 hybrids. We will employ B6xD2 recombinant inbred strains to determine the number and chromosomal locations of reprogramming factor genes that account for this difference. We will combine those data with array expression data for known transcription factors and chromatin regulators to identify candidates, and then perform functional studies to confirm which genes determine reprogramming capacity of the oocyte. This combined genetic and molecular approach, built on a foundation of phenotype difference will thus result in identification of novel reprogramming factors.
There is great interest in identifying factors in the egg that are responsible for nuclear programming during cloning, because such knowledge may lead to enhanced methods for generating stem cells, and for cloning animals for a range of basic and applied purposes. The difficulty is how to determine which of the myriad of expressed transcription factors and chromatin regulators in the egg are responsible for reprogramming capacity in mice, and we have obtained already a wealth of array expression data for the relevant mouse strains. We will combine these data here to identify gene mapping, gene expression, and functional studies those specific genes that determine oocyte reprogramming capacity, and hence serve as key oocyte reprogramming factors.
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