Telomerase and self-renewal in human embyronic stem cells

Funding Type: 
SEED Grant
Grant Number: 
ICOC Funds Committed: 
Disease Focus: 
Amyotrophic Lateral Sclerosis
Neurological Disorders
Spinal Cord Injury
Neurological Disorders
Stem Cell Use: 
Embryonic Stem Cell
Public Abstract: 
Embryonic stem cells are unique in their ability to give rise to all mammalian tissues. Their potential application to human disease is enormous because they could be employed to repair or replaced damaged tissue. Although tremendous strides have been made in recent years in treating human disease, replacing damaged tissue remains almost completely beyond our grasp. Harnessing human embryonic stem cells for this purpose will open completely new areas of regenerative medicine. One shared characteristic of embryonic stem cells and adult stem cells that reside in many of our tissues is the ability to self-renew. Self-renewal is the ability of a stem cell to divide and give rise to a daughter cell that is undifferentiated and capable of giving rise to all the same lineages as the parent stem cell. Understanding how embryonic stem cells self-renew is critical for determining how to maintain these cells, how to differentiate them toward specific tissue lineages and how to expand more committed stem cells or progenitor cells in cell culture. A small number of genes that control embryonic stem cell self-renewal have been discovered, but our understanding of this process remains in its infancy. In this proposal, we investigate the molecular mechanism by which telomerase contributes to embryonic stem cell self-renewal. Telomerase is an enzyme complex expressed in embryonic stem cells, some tissue stem cells and in almost all human cancers. Most differentiated cells lack telomerase expression. Telomerase adds DNA repeats to structures at the ends of our chromosomes, termed telomeres. Telomeres are very important in protecting chromosome ends and in preventing chromosome ends from breaking down or sticking to other ends inappropriately. By maintaining telomeres, telomerase supports the ability of stem cells to divide a large number of times. In addition to its function in telomere synthesis, we recently discovered a second role for telomerase. We expressed the TERT protein component of telomerase in mouse skin and unexpectedly found that TERT activated resting tissue stem cells. Activation of skin stem cell by TERT triggered a regenerative program in skin leading to robust hair growth. We used a rigorous technique to show that this new activity does not involve TERT’s other role in telomere lengthening. It is absolutely essential to understand how telomerase carries out its functions in stem cells. Therefore, we have isolated proteins that strongly interact with TERT. In this proposal, we investigate the function of TERT in embryonic stem cells and determine the role of several TERT associated proteins in embryonic stem cell self-renewal.
Statement of Benefit to California: 
This proposal will benefit California and its citizen in two general ways. First, I have recruited two new scientists to California from Texas to work on this proposal. These are new taxpayers and consumers, which will benefit local businesses. They would have been less likely to come to California in the absence of the CIRM grant program. Second, this novel grant will generate new intellectual property in the form of patents. These patents may in fact be licensed to California companies or be used to support the formation of new start-up companies. The growth of such companies has historically fueled much of the profound growth in California. The future of California is linked to new technologies in the stem cell, biotechnology and other technology sectors.
Progress Report: 
  • A main goal of research in our laboratory is to identify strategies to promote neural repair in spinal cord injury and related neurological conditions. On the one hand, we have been using mouse models of spinal cord injury to study a long-standing puzzle in the field, namely, why axons, the fibers that connect nerve cells, do not regenerate after injury to the brain and the spinal cord. On the other hand, relevant to this CIRM SEED grant, we have started to explore the developmental and therapeutic potential of human embryonic stem cells (hESCs) for neural repair. We do this by first developing a method to genetically manipulate a HUES line of hESCs. The advent of hESCs has offered enormous potential for regenerative medicine and for basic understanding of human biology. To attain the full potential of hESCs as a tool both for therapeutic development and for basic research, we need to greatly enhance and expand our ability to genetically manipulate hESCs. A major goal for our SEED grant-sponsored research is to establish methods to genetically manipulate the HUES series of hESC lines, which are gaining wide utility in the research community due to the advantages on their growth characteristics over previously developed hESC lines. The first gene that we targeted in HUES cells, Fezf2, is critical for the development of the corticospinal tract, which plays important roles in fine motor control in humans and hence represents an important target for recovery and repair after spinal cord injury. By introducing a fluorescent reporter to the Fezf2 locus, we are now able to monitor the differentiation of hESCs into Fezf2-expressing neuronal lineages. This work has been published. A second goal is to start to explore the developmental and therapeutic potential of these cells and cells that derived from these cells in the brain and spinal cord. We are currently utilizing the cell line genetically engineered above to develop an efficient method to differentiate HUES cells into subcerebral neurons. Results so far have been encouraging. Efforts are also underway to overexpress Fezf2 as a complementary approach to drive the differentiation of HUES cells into specific neuronal types. Together, these studies will lay down the foundation for therapeutic development with HUES cells and their more differentiated derivatives for neurological disorders including spinal cord injury where neural regeneration can be beneficial. The CIRM SEED grant has allowed us to pursue a new, exciting path of research that we would have not pursued had we not been awarded the grant. Furthermore, the CIRM funded research has opened a new window of opportunity for us to explore genetic engineering of hESCs to model human neurological conditions in future.

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