Russell B. Fletcher, Ph.D. - US grants

[unreadable] DESCRIPTION (provided by applicant): The long-term objective of this research project is to understand the cellular events that regulate progenitor cells and neurogenesis. This study will use genetic approaches to understand the signaling mechanisms that regulate the cell fate decisions in the development of the diverse cell-types of the olfactory epithelium. The olfactory epithelium is a sensory epithelium that constantly renews neurons from progenitor cells and can regenerate upon injury. The development of the olfactory epithelium involves the establishment and maintenance of progenitor cells, neurogenesis of olfactory receptor neurons, and formation of support cells called sustentacular cells. However, the regulation of these cell-fate decisions is not understood. The simple, well-defined architecture and the availability of cell-type and differentiation-state specific markers make the olfactory epithelium an excellent model for studying the processes of neurogenesis and progenitor cell regulation. There is evidence that Bone Morphogenetic Protein (BMP) signaling is involved in olfactory epithelial development. This study will first define which BMP signaling components are present in specific cell types of the olfactory epithelium, and secondly, activation of BMP signaling will be assessed. Subsequently, genetic loss-of-function mutants in specific BMP signaling components will be investigated to determine how specific BMP signaling regulates progenitor maintenance and neurogenesis. This will involve analyzing mutants for changes in a range of cell-type and differentiation-state specific markers, cell proliferation, and cell death. Ultimately this study should provide insight into how BMP signaling regulates these processes, and it will lay the foundation for future studies on signaling pathway interactions and the regulation of regeneration. The olfactory epithelium contains thousands of neurons that sense volatile chemicals in the environment, and it renews these neurons throughout life and can regenerate upon injury. However, the molecular and cellular mechanisms that regulate the establishment of this tissue are poorly understood. Understanding how a regenerative tissue is established at the molecular and cellular level has great promise for gaining insights into how to deal with damage and disease of neural tissue. [unreadable] [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Adult stem cells underlie tissue homeostasis and regeneration. Because all adult tissues degrade with age, understanding how adult tissue stem cells decline in function with age is an important problem. The overall goal of my research is to integrate a range of genetic, genomic, biochemical, and biophysical approaches to elucidate the molecular mechanisms that underlie gene regulation and control changes in stem and progenitor cell function during tissue development, maintenance and regeneration, and ultimately, degeneration; i.e. what are the molecular underpinnings that control how structured, plastic biological form is made, maintained and reformed, and finally degraded. We do not understand the mechanisms responsible for the age-related decline in neural stem cells. My career development plan for this K01 award involves coursework, seminars, and direct interaction with labs and mentors that in sum will provide me with expertise in high throughput sequencing (HT-Seq) and computational genomics and a strong background in the molecular mechanisms of aging. I want to then combine the HT-Seq and computational genomic methods to complement the genetic, molecular, and biochemical approaches I have already been employing to investigate the mechanisms underlying age- related decline in stem cell function in the olfactory epithelium. My proposed research focuses on understanding the age-related changes that occur in the olfactory epithelial neural stem cells that underlie the age-related decline in neurogenesis and tissue regeneration. The olfactory epithelium (OE) is a sensory neuroepithelium that supports adult neurogenesis and tissue regeneration following injury. As in the sites of neurogenesis in the central nervous system, its renewal and regenerative capacity decreases with age. The OE is characterized by two stem cell populations: the horizontal basal cells (HBCs) are mostly quiescent and function as reserve stem cells to regenerate the OE following injury, and the globose basal cells (GBCs) are a heterogeneous population of stem and progenitor cells that underlie normal tissue homeostasis by continually renewing the neuronal population. The OE provides an excellent model for investigating the molecular mechanisms that mediate age-related changes in reserve and active stem cell function during neurogenesis in vivo. We plan to test the hypothesis that the age-associated reduction in neurogenesis and regenerative capacity in the OE is due to a depletion of the committed progenitor subpopulation of GBCs and the inability of the HBC and GBC stem cells to proliferate and differentiate. Using specific combinations of transgenic reporter lines, immunohistochemistry to genes expressed by specific stem and progenitor cell populations, and mitotic label retention experiments, we will characterize how the cellular dynamics and function of the different stem and progenitor cells of the OE change with age. We will then perform RNA-Seq to thoroughly characterize the transcriptome of young and aged subpopulations of neural stem cells. Together, this will allow us to discern in a highly quantitative manner which genes are differentially expressed and which splice-variants utilized in young versus aged reserve and active stem cells. This line of inquiry has the potential to identify age-related changes in stem cells, and the challenge will be to define the proximate causes and determine if they can be modified or reversed. The knowledge gained from such endeavors may also inform approaches to cell replacement therapies and modeling of age-related disease.