Characterization of factors involved in the regulation of chromatin structure and human stem cell pluripotency

Funding Type: 
SEED Grant
Grant Number: 
RS1-00308
ICOC Funds Committed: 
$0
Disease Focus: 
Diabetes
Stem Cell Use: 
Embryonic Stem Cell
Public Abstract: 
Unlike the majority of cells in the human body, stem cells can give rise to a wide variety of different cell types. This unique property – pluripotency – is the foundation of virtually all proposed uses of stem cells in regenerative medicine. Understanding the mechanisms that regulate stem cell pluripotency will facilitate the development of new approaches for isolating and culturing human stem cells in the laboratory and manipulating their development in the human body. Accordingly, the molecular mechanisms underlying the control of stem cell pluripotency and differentiation are currently a topic of intense interest. Members of the Polycomb group of regulatory proteins play important roles in the maintenance of stem cell pluripotency by repressing genes involved in cellular differentiation. A major question in the field of stem cell biology concerns how Polycomb repression is “switched off” to permit the differentiation of stem cells into specialized cell types. Although the molecular nature of this switch is unknown, genetic studies in simple model organisms have suggested that the human CHD7 protein plays a critical role in this process by counteracting Polycomb repression. The goal of our research is to test this hypothesis and determine the role of CHD7 in the control of stem cell pluripotency and differentiation. The proposed research may lead to novel approaches for the development of diagnostics, tools and therapies. If our hypothesis about the role of CHD7 in human stem cell development is correct, drugs that interfere with CHD7 function could be used to maintain or regulate stem cell pluripotency, either in culture or in patients. Such drugs might also prove extremely useful for creating new stem cell lines for use in regenerative medicine. An added benefit of our research is that it may suggest new treatments for CHARGE syndrome, a serious development that affects one in eight thousand births.
Statement of Benefit to California: 
Pluripotency – the ability to differentiate into a seemingly unlimited variety of cell types – is a distinguishing feature of stem cells and the foundation of their potential uses in regenerative medicine. Recent studies have suggested that the human CHD7 protein may function as a genetic switch that triggers the differentiation of stem cells into specialized cell types. The information gained from the proposed research on CHD7 may facilitate the creation of new stem cell lines as well as new approaches for regulating stem cell pluripotency and differentiation in both the laboratory and the human body. In addition, the proposed research may permit the development of more effective treatments for CHARGE syndrome, a serious developmental disorder resulting from mutations in CHD7 that affects one in 8,000 births.
Progress Report: 
  • The goals of this proposal are to investigate endodermal differentiation and proliferation of human ES cells in culture. Endodermal differentiation is a necessary step towards making pancreatic beta cells, as well as other endodermal cells such as liver cells. Pancreatic beta cells generated from human ES cells could be used to treat type I diabetics. In the past two years, we have incorporated human ES cell culture technology into our laboratory and have been able to replicate data obtained by other research groups. While several other research groups and companies around the world are focused on making pancreatic beta cells as quickly as possible, we strongly believe that a more detailed understanding of the biology of human ES cell differentiation into endoderm will help the optimization of this protocol. Therefore, we have focused our efforts on testing a number of variables in the initial step of creating definitive endoderm. We have found that different human ES cell lines have very different capacity to differentiate into endoderm under the same culture conditions. In addition, we have recently focused our research effort on the post-translational modifications of key regulators of endoderm differentiation, and found a critical role for a poorly appreciated modification, namely a sugar modification called GlcNAcylation. In summary, developing a reproducible and efficient way to differentiate human ES cells into endoderm, as well as a thorough understanding of this key step, will allow us and others to elucidate the detailed set of molecular and biochemical events underlying this critical differentiation step, and will improve differentiation protocols.
  • The goals of this proposal are to investigate endodermal differentiation and proliferation of human ES cells in culture. Endodermal differentiation is a necessary step towards making pancreatic beta cells, as well as other endodermal cells, such as liver cells. Pancreatic beta cells generated from human ES cells could be used to treat type I diabetes. In the past two years, we have incorporated human ES cell culture technology into our laboratory and have been able to replicate data obtained by other research groups. While several other research groups and companies around the world are focused on making pancreatic beta cells as quickly as possible, we strongly believe that a more detailed understanding of the biology of human eS cell differentiation into endoderm will help the optimization of this protocol. Therefore, we have focused our efforts on testing a number of variables in the initial step of creating definitive endoderm. We have found that different human ES cell lines have very different capacity to differentiate into endoderm under the same culture conditions. IN addition, we have recently focused our research effort on the post-translational modifications of key regulators of endoderm differentiation, and found a critical role for a poorly appreciated modification—namely a sugar modification called GlcNAcylation. In summary, developing a reproducible and efficient way to differentiate human ES cells into endoderm, as well as thorough understanding of this key step, will allow us and others to elucidate the detailed set of molecular and biochemical events underlying this critical differentiation step, and will improve differentiation protocols.
  • We initiated a project on the role of post-translational modifications during hES cell differentiation into endodermal lineages, specifically on the GlcNAcylation sugar modification. We found that this modification appears to be important for endoderm formation in hES cell cultures. Identification of modified proteins is an important next step in understanding the mechanisms of this phenomenon and may ultimately provide a basis to develop assays for screening drugs that enhance endoderm/beta-cell formation.

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