Epithelial stem cell fate and epigenetic reprogramming – EPIStem

This proposal originates from the discovery of the gene, Pw1, implicated in adult stem cells. As described in the preceding sections, our laboratory identified PW1 in a search for early developmental regulators of the skeletal muscle lineage. We subsequently demonstrated that PW1 regulates 2 key cell stress pathways (p53 and inflammation) that contribute to stem cell mobilization in response to injury and age. We have recently generated a reporter mouse line (described above) that has made analyses of PW1 postnatal expression simpler and more reliable. Importantly, reporter gene expression is very strong allowing us to use cell sorting techniques to purify PW1+ cells to > 98% purity. The combination of these recent advances in our laboratory allowed us to make the astonishing discovery that the Pw1nlacZ/+ mice not only allow us to easily identify and purify stem cells from postnatal skeletal muscle, but serve to identify stem cells in many other adult tissues including the CNS, blood, gut, eye (and lens) and skin, the latter being the focus of this project and a new direction for our group. It is reasonable to assume that the Pw1nlacZ/+ mice line will prove to be a significant tool for many research efforts nationally and internationally. To reach this stage however, a complete analysis is required in at least 2 tissues. As this analysis is being carried out in skeletal muscle (and funding is not requested here for this project), we have chosen the skin as a focus given the advanced state of the field and the relative ease this system offers for experimental manipulation. To date, only one other mouse model has been generated by the group of Hans Clevers (Lgr5) which identifies some stem cells in several tissues, however a description of the full range of stem cell expression remains incomplete. This project extends from our recently published results using PW1 expression to identify a novel resident population in postnatal skeletal muscle to a complete and novel project on the skin. We will also take advantage of the relative accessibility of the skin and the ease with which it can be manipulated and gene expression regulated to extend our studies to elucidate potential functions of PW1 in vivo. Lastly, our ongoing studies show that PW1 (and the transgene) expression is epigenetically regulated during stem cell activation in response to injury and importantly, during aging. Changes in stem cells with age that may explain the overall decrease in regenerative capacity are poorly characterized, and as such, our studies proposed here represent a major step forward. The last aim, in which we propose to identify potential regulators of stem cell epigenetic changes, if successful, will impact the private domain as well as for potential therapeutic approaches and is a timely subject in today’s society in which the aging population is an ever increasing segment of modern society.