Extended low dose radiation is encountered in the natural environment (for example, radon exposure), through frequent exposure to medical diagnostics (X-rays), and in occupational situations.  However, the effects of these exposures on human cell and tissue types and the molecular pathways through which such effects occur still need further investigation. In particular, while numerous sources of evidence indicate that epigenetic changes can be caused by low dose radiation, there is a lack of systematic data in the same cell types and at the same doses to connect such chromatin level changes to gene transcription and protein expression changes all the way to cell phenotype alterations. We propose to examine the impact of low dose gamma radiation on the cell types that make up the human lung: fibroblast, epithelial, and endothelial cells. Our overarching objective is to connect observable changes in cell function (phenotypes) with the molecular alterations that cause these cell function changes.  We will accomplish this goal by first monitoring changes in cellular function: as cells are exposed to radiation, do fibroblasts become reactive and fibrotic? Do endothelial and epithelial cells lose their ability to form a barrier or undergo an epithelial to mesenchymal transition? Does DNA damage occur and cell proliferation change?  Then, we will collect genome-wide information about which genes are transcribed (transcriptomics), which proteins are made (proteomics), and how epigenetic marks along the DNA change in response to this low dose radiation.  We will use mechanistic as well as data driven computational models to connect these molecular level changes to observed cell phenotypes. Based on our prior data that radiation can change the structure of chromosomes, we will test the hypothesis that extended low dose radiation induces changes in the epigenetic marks along the DNA, which can encode a memory of the cellular exposure and lead to long term changes in gene and protein expression and therefore cell function.  Humans can be impacted by several different types of low dose radiation, and these different radiation types may have different biological effects.  Therefore, we will extend our study to compare the effects of low dose X-rays/gamma rays to the effect of low dose alpha particle exposure, such as occurs in a natural setting in the form of chronic radon exposure.  To better represent a natural tissue or organ context, we will also compare the results for single cell types cultured in a dish to the impact of low dose radiation on cells grown in spheroids and co-cultured in lung-like organoids. The results of our research will help identify biomarkers that can be used to track whether a tissue is experiencing negative consequences of radiation exposure. Further, the models we develop will enable prediction of the effect of low dose radiation in other scenarios.