Bright/ARID3A was initially discovered for its role in immunoglobulin heavy chain transcription in the mouse. Bright has also been implicated as a target of p53 and as an E2F binding partner. We have previously shown that Bright is necessary for hematopoietic stem cell development in the embryo. In this work, we show that Bright has a much broader role in development than previously appreciated. Loss of Bright in mice usually results in embryonic lethality due to lack of hematopoietic stem cells. Rare survivor mice initially appear smaller in size than either wildtype or heterozygous littermates, but as they age, these differences diminish. We show that adult Bright null mice have age-dependent kidney defects. Previous work in the adult mouse has not indicated a role for Bright in kidney function. We observed an increase in cellular proliferation in Bright null kidneys, indicating a possible mechanism behind our observation. Loss of Bright has recently been implicated in causing developmental plasticity in somatic cells. Our data indicate that loss of Bright is sufficient to fully reprogram mouse embryonic fibroblasts (MEFs) back to a pluripotent state. We term these cells Bright repression induced pluripotent stem cells (BriPS). BriPS derived from Bright knockout MEFs can be stably maintained in standard embryonic stem cell culture conditions: they express pluripotency markers and can form teratomas in vivo. We further viii show that Bright is active during embryonic stem cell differentiation. Bright represses key pluripotency genes, suggesting the mechanism of reprogramming may be Bright’s direct repression of key pluripotency factors in somatic cells. Recent advances in inducing pluripotency in somatic cells (iPS cells) have created a new field of disease modeling, increased our knowledge of how pluripotency is regulated, and introduced the hope that they can be adapted to treat disease. However, current methods for producing iPS involve overexpression of potentially oncogenic transcription factors, leaving a large gap between the lab and the clinic. Our results mark the first demonstration of an alternative method to reprograming somatic cells that is not mediated by overexpression of pluripotency factors. / text

The field of stem cell research has been growing more because of the interest in using stem cells to cure diseases and heal injuries. Human embryonic stem cells, because of the controversy surrounding them—and subsequently the difficulties in acquiring samples of the existing aging cell lines—can only be used in limited capacities. While the development of induced pluripotent stem cells in the last decade has allowed the field to progress closer to medical treatments, the low efficiency of reprogramming a somatic cell to a pluripotent state, and the vast molecular and genomic differences between human embryonic stem cells and human induced pluripotent stem cells is still an issue. Therefore, the goal is to discover methods, chemicals, and factors that can reduce these differences and increase the efficiency of inducing pluripotency. This proposal aims to look at the effects of the protein ECAT1 in inducing pluripotency in human somatic cells. Little is known about ECAT1, otherwise known as Embryonic Stem Cell-Associated Transcript 1, beyond its presence in human embryonic stem cells and oocytes and its absence in differentiated cells. While originally considered by scientists during the development of the reprogramming technique, ECAT1's effects have not been tested in humans. Therefore, a series of experiments will be performed in which ECAT1 will be used in conjunction with OSKM to induce pluripotency in adult human dermal fibroblasts, which will then be differentiated into spinal motor neurons. The three stages of this proposal--inducing pluripotency, comparing pluripotencies in the reprogrammed cells and embryonic stem cells, and differentiating the stem cells--should answer questions about ECAT1 and the reprogramming process. It is predicted that ECAT1 should reduce the genomic and molecular differences between embryonic stem cells and induced pluripotent stem cells. ECAT1's presence should also increase the efficiency of reprogramming as well as successful differentiation to other cell types.