Overall, our biggest breakthrough this year has been the identification of a link among the sugars on the cell surface, a label free electrical measure reflecting the type of mature cell the stem cells will become (membrane capacitance), and stem cell fate potential, or the ability of the cell to form a particular type of mature cell. Stem cells generate mature, functional cells after proteins on the cell surface interact with cues from the environment encountered during development or after transplantation. Thus, these cell surface proteins are critical for directing transplanted stem cells to form the appropriate types of cells to treat injury or disease. A key modification regulating cell surface proteins is glycosylation, which is the addition of sugars onto proteins and has not been well studied in neural stem cells. Our project focuses on a major unsolved problem in the neural stem cell field: do different proteins coated with sugars on the surfaces of cells in this lineage (neuron precursors, NPs and astrocyte precursors, APs) determine what types of mature cells will form? We hypothesize key players directing cellular decisions are glycosylated proteins controlling how precursors respond to extracellular cues. This year on the project, we found a particular glycosylation pathway that adds highly branched sugars regulates cell surface properties and controls the decision to form either a neuron or an astrocyte. In the next year of the project, we will explore this pathway further and perform experiments to identify the proteins on the cell surface important for determining the formation of either mature neurons or astrocytes. By answering these questions, we will better understand the regulation of NPs and APs, which will improve the use of these cells to treat brain and spinal cord diseases and injuries.
Reporting Period:
Year 2
Our project focuses on a major unsolved problem in the neural stem cell field, which is how cells in this lineage respond to cues in the external environment and decide what type of mature cells to form. Interaction of proteins on the cell surface with cues from the environment encountered during development or after transplantation can induce stem cells to generate particular types of mature, functional cells. Thus, cell surface proteins are critical for directing transplanted stem cells to form the appropriate types of mature cells to treat injury or disease. A key modification regulating cell surface proteins is glycosylation, which is the addition of sugars onto proteins and has not been well studied in neural stem cells. We hypothesize key players directing cellular decisions are sugar-coated proteins controlling how stem cells respond to extracellular cues. This year on the project we used a novel approach that doesn’t require any cell-type specific labels to enrich cells in the neural stem cell lineage that preferentially form the mature cell type astrocytes (astrocyte precursor cells). Enriched astrocyte precursors show more activity in a particular glycosylation pathway that adds highly branched sugars to proteins. If we push cells to form more highly branched sugars, they shift in the types of mature cells they will form and generate fewer neurons. We are using protein analysis with large data sets to determine what types of proteins are preferentially sugar-coated as cells are forming different types of mature cells. Our goal is to better understand the regulation of how the mature cells, particularly astrocytes and neurons, are formed, which will improve the use of these cells to treat brain and spinal cord diseases and injuries.
Reporting Period:
Year 3
Our project focuses on a major unsolved problem in the neural stem cell field, which is how cells respond to cues in the external environment and decide what type of mature cells to form. Interaction of proteins on the cell surface with signals in the transplantation environment can induce stem cells to generate particular types of mature, functional cells. Thus, cell surface proteins are critical for directing transplanted stem cells to form the appropriate types of mature cells to treat injury or disease. A key modification regulating cell surface proteins is glycosylation, which is the addition of sugars onto proteins and has not been well studied in neural stem cells. We hypothesize key players directing cellular decisions are sugar-coated proteins controlling how stem cells respond to extracellular cues.
This year on the project we found that inherent electrical properties of cells in stem cell populations can be used to isolate them from other types of cells. We made new devices that use a novel approach without cell labeling to enrich cells that preferentially form the mature cell type astrocytes (astrocyte precursor cells). The new device is faster and gives better sorting than our previous versions. Enriched astrocyte precursors have more activity in a particular glycosylation pathway that adds highly branched sugars to proteins. We found these sugars are not just markers revealing what type of mature cells will form, but actively direct the emergence of mature cells. Cells pushed to have more of these sugars resist forming mature cells and when they do mature, the types of cells that form shift depending on the available external cues. We analyzed large data sets to identify proteins changed on the cell surface as cells form different types of mature cells. Our goal is to better understand the development of mature cells, particularly astrocytes and neurons, which will improve the use of these cells to treat brain diseases and injuries.
Reporting Period:
Year 4/NCE
Our project focused on a major unsolved problem in the neural stem cell field, which is how cells respond to cues in the external environment and decide what type of mature cells to form. Interaction of proteins on the cell surface with signals in the transplantation environment can induce stem cells to generate particular types of mature, functional cells. Thus, cell surface proteins are critical for directing transplanted stem cells to form the appropriate types of mature cells to treat injury or disease. A key modification regulating cell surface proteins is glycosylation, which is the addition of sugars onto proteins and has not been well studied in neural stem cells.
We studied the surfaces of human neural stem cells and found that inherent electrical properties of the cell membrane can be used to detect fate without the use of labels. Further studies identified cell surface glycosylation as the primary contributor to the electrical properties that delineate stem cell fate. The electrical properties of stem cells of distinct fates are different enough to allow them to be isolated from each other. Based on this, we made new devices to enrich cells that preferentially form the mature cell type astrocytes (astrocyte precursor cells). The new device is faster and gives better cell enrichment than our previous sorting platforms. Enriched astrocyte precursors have more activity in a glycosylation pathway that adds highly branched sugars to proteins. We found these sugars are not just markers revealing what type of mature cells will form, but actively direct the emergence of mature cells. We analyzed large data sets to identify proteins changed on the cell surface as cells form different types of mature cells. Our goal is to better understand the development of mature cells, particularly astrocytes and neurons, which will improve the use of these cells to treat brain diseases and injuries.
Stem cells generate mature, functional cells after proteins on the cell surface interact with cues from the environment encountered during development or after transplantation. Thus, these cell surface proteins are critical for directing transplanted stem cells to form appropriate cells to treat injury or disease. A key modification regulating cell surface proteins is glycosylation, which is the addition of sugars onto proteins and has not been well studied in neural stem cells. We focus on a major unsolved problem in the neural stem cell field: do different proteins coated with sugars on the surfaces of cells in this lineage (neuron precursors, NPs and astrocyte precursors, APs) determine what types of mature cells will form? We hypothesize key players directing cellular decisions are glycosylated proteins controlling how precursors respond to extracellular cues. We will address this hypothesis with aims investigating whether (1) glycosylation pathways predicted to affect cell surface proteins differ between NPs and APs, (2) glycosylated proteins on the surface of NPs and APs serve as instructive cues governing fate or merely mark their fate potential, and (3) glycosylation pathways regulate cell surface proteins likely to affect fate choice. By answering these questions we will better understand the formation of NPs and APs, which will improve the use of these cells to treat brain and spinal cord diseases and injuries.
Statement of Benefit to California:
The goal of this project is to determine how cell surface proteins differ between cells in the neural lineage that form two types of final, mature cells (neurons and astrocytes) in the brain and spinal cord. In the course of these studies, we will uncover specific properties of human stem cells that are used to treat neurological diseases and injuries. We expect this knowledge will improve the use of these cells in transplants by enabling more control over what type of mature cell will be formed from transplanted cells. Also, cells that specifically generate either neurons or astrocytes can be used for drug testing, which will help to predict the effects of compounds on cells in the human brain. We hope our research will greatly improve identification, isolation, and utility of specific types of human neural stem cells for treatment of human conditions. Furthermore, this project will generate new jobs for high-skilled workers and, hopefully, intellectual property that will contribute to the economic growth of California.
