Specific ion flows: a novel signal mediating stem cell-niche communication

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DESCRIPTION (provided by applicant): The regeneration of pattern following injury and the maintenance of form during normal cellular turnover requires the participation of adult stem cells. In order to understand and ultimately learn to control these processes for biomedical applications, it is necessary to identify the molecular mechanisms by which stem cells communicate with their neighbors. Such communication is needed for stem cells to know where, when, and how to differentiate. Because fundamental cellular control mechanisms are widely conserved, and because we believe fundamental progress can be made in systems that are amenable to the molecular investigation of a recognizable adult stem population, we propose study stem cell interactions in vivo by capitalizing on a powerful model system: the planarian Schmidtea mediterranea. These complex flatworms are able to replace any part of their body using a recognizable adult stem cell population: the neoblasts. This is an ideal system in which to investigate the molecular signals sent to and from neoblasts. In contrast and complement to the field's focus on biochemical factors, our lab studies roles of endogenous ion flows, and pH and voltage gradients in controlling cell proliferation, migration, and differentiation. We will test the hypothesis that a large component of the local and long-range signals controlling stem cell behavior within their environment is bioelectrical, consisting of the physiological results of specific ion channel and pump activity. We will characterize the involvement of several channels, pumps, and gap junctions in controlling stem cell positional information and their contribution during regeneration. We propose two main aims: 1) molecular validation (using RNAi) of several candidate channel and pump proteins involved in neoblast-mediated events, followed by their expression analysis and a detailed characterization of their roles in regeneration and remodeling; and 2) characterization of the bioelectrical properties of stem cells as they progress through the different phases of differentiation and development of functional techniques to control neoblast movement, proliferation, and differentiation in vivo. The expertise which our group has developed with this field in embryonic development and regeneration in several vertebrate and invertebrate systems will allow rapid and important progress to uncover novel aspects of stem cell regulation, and will result in the high-reward outcome of an entirely new set of controls of stem cell signaling, which ultimately will be used to drive biomedical applications aiming to induce regeneration in adult cells of the patient. This work is an ideal fit for the Cancer, Aging, and Biomedical Imaging and Bioengineering Institutes because we propose to use novel imaging and biophysical manipulation techniques to enable medical applications in which adult stem cells can be induced to properly replace aging, damaged, or cancerous tissue. Our work will lead to the understanding of how adult stem cells allow some animals to perfectly repair any part of their body. This information will be used to develop methods whereby regeneration of tissues, organs, and appendages may be induced in human patients following injury, aging, or tumor growth.