The Role of Ion Channels in the Differentiation of Embryonic Stem Cells

Funding Type: 
SEED Grant
Grant Number: 
ICOC Funds Committed: 
Disease Focus: 
Blood Disorders
Stem Cell Use: 
Embryonic Stem Cell
Public Abstract: 
Stem cells have unique potential to cure human disease. Their ability to give rise to virtually any type of cell has given hope to the public for curing all types of ailments. For this reason, stem cells continue to capture the headlines of the mass media and esteemed scientific journals. Embryonic stem cells (ESCs) are probably the best known stem cell available to researchers. Most of our knowledge about these important cells comes from studies in animals, particularly in mice. Recent animal studies have revealed amazing success at curing neurological diseases such as Parkinson's Disease (PD). It is no coincidence that progress has been made first in the area of the brain. The nervous system seems to be the default pathway for many stem cell lines that have been studied. The research proposed here endeavours to discover why the cells follow this pathway. The cells we will study are those that have the most benefit to patients, human embryonic stem cells (hESCs). We know that as stem cells become nerve cells (when they mature or differentiate), they develop special abilities as part of their function in the brain. They must carry electrical signals to function. These electrical properties are akin to the signal carried to your TV by a cable. The signal has to propagate to your TV through the signal cable. Neurons do the same thing using special proteins called ion channels. Ion channels are proteins stuck in the cell membrane that allow small ions like sodium and potassium to move back and forth across the cell membrane to change their electrical state. These channels have been implicated in many human diseases. Their proper functioning is critical to human health. The research proposed here seeks to understand how these channels affect the differentiation of hESCs. That is, we want to find out exactly what type of ion channels are made by stem cells as the mature into brain cells. We also want to know when the ion channels are made by the cells. Thus we hope to discover the function of ion channels in the differentiation of these important cells. Once we have this knowledge we can begin to manipulate the channels to affect stem cell differentiation or their cellular fate. That is, we want to be able to make the cells mature into the type of cell we need. There are many known molecules that are known to affect ion channel function. Some of these open the channels and some of them block them. By using these agents, we can manipulate the function of the ion channels to make the stem cells follow a certain fate. This knowledge will be another tool scientists can use to manipulate the stem cell fate. The more we can fine tune the differentiation of stem cells, the better we will be at designing therapies to cure any number of human diseases.
Statement of Benefit to California: 
The research project proposed here seeks to understand how ion channels affect the differentiation of human embryonic stem cells (hESCs). The ability to direct the differentiation of these cells has high potential for use in alleviating a variety of diseases. This will potentially have tremendous medical benefit to the people of California. Funding of this work will also employ and allow the training of up to 4 University students, one technician, and one faculty collaborator in human stem cell work. This training will benefit the State of California by creating trained stem cell workers that will continue to keep our work force well trained and competitive in this growing field.
Progress Report: 
  • A prominent subset of white blood cells, named CD4 helper T cells, are critical in modulating the immune response against viral and bacterial pathogens. During HIV infection, the CD4 compartment is selectively reduced, suppressing the activity and response of cytolytic CD8 T cells, needed to abolish cells infected with the virus. Pharmaceutical therapies have been developed but they are not consistently effective and multidrug resistant viral strains are increasingly prevalent. Similarly, in vitro manipulated human dendritic cells are now being explored to tolerize against autoimmune disease or to stimulate antitumor responses. However, the number of dendritic cells that can be isolated form patients using current technologies is small. Consequently, different approaches need to be developed to enhance T cell reconstitution. In principle, multipotent hematopoietic progenitors could be derived from hESCs without long-term in vitro culture. A drawback is that the number of human hematopoietic progenitors derived from human ES cell cultures is limited using current culture conditions. Consequently, a subset of studies involving in vitro manipulated human cells would be difficult to perform. The transduction of human progenitor cells can be achieved using a tissue culture system in which human cord blood progenitors are differentiated in the presence of stromal cells that express the Notch ligand DL-1 towards the T cell lineage. However, the efficiency by which human progenitor cells differentiate into the T lineage cells is low. In the original application we proposed to develop a novel strategy that would permit the generation of large numbers of human T cell progenitors (up to 109) from human hematopoietic stem cells. To accomplish this objective we would target a critical regulator of early hematopoieisis, named E2A. Indeed during the two years period funded by CIRM we have demonstrated that murine hematopoietic progenitors that overexpress an inhibitor of E2A, named Id2, can be grown indefinitely in culture without losing their ability to generate many different types of white blood cells in the laboratory. This strategy is unconventional since it would permit the growth and isolation of large numbers of T cell progenitors, which has not been achieved so far by conventional culture conditions. We will continue these studies and use the same strategy to establish a long-term culture of human hematopoietic progenitor cells. If successful the approach would enable clinicians to reconstitute the hematopoietic compartments of patients carrying invading pathogens, including HIV infected patients, with large numbers of T cells that either express either a wild-type TCR repertoire or TCRs with specificities directed against invading pathogens. I expect this to succeed since we have already achieved this objective using murine progenitors as demonstrated during the past two years using funds obtained form the CIRM.

© 2013 California Institute for Regenerative Medicine