Exploring embryonic exposure to hypoxia as a priming cue for postnatal epidermal insult

About This Grant

Project summary/abstract In barrier tissues, developmental transcription factors are often reactivated in cases of disease or inflammation to drive expression of a suite of embryonic genes. While this reuse of pathways can prompt the increased proliferation or migration characteristic of both states, other times the reason for repeated activity is less clear. As an example, HIF1α activity during epidermal development within the hypoxic womb of most mammals does not contribute to generation of proper skin structure, but reactivation after wounding is critical for appropriate healing. One possible explanation for this bimodal activity is that the first wave of activation, during development, might regulate the second wave. Prior work has demonstrated that epithelial stem cells are capable of learning from their experiences, encoding epigenetic memories to respond to a stimulus more quickly the second time encountered. These epigenetic memories are evident at the chromatin level as maintained accessibility of stress-induced loci. If a similar phenomenon is active during development, it could serve to prime epidermal stem cells to respond to inflammatory cues later in life. This hypothesis will be tested by modulating HIF1α activity during embryonic epidermal development and carefully assessing resultant molecular changes. In utero lentiviral delivery of Cre to Hif1a fl/fl embryos will selectively prevent epidermal Hif1a induction in the post-gastrulation embryo. Preliminary work supports that HIF1α is dispensable for skin morphogenesis but drives substantial transcriptional changes in epidermal stem cells. Notably, expression of hypoxia-induced target genes and chromatin-modifying enzymes is altered in the absence of HIF1α. After further characterizing molecular changes, focusing on the chromatin landscape, next experiments will leverage inducible systems to selectively perturb the first wave of HIF1α activity, leaving postnatal activity intact. Inflammatory challenge of these animals will reveal whether embryonic HIF1α activity has lifelong effects on stem cell function, as hypothesized. Moreover, bioinformatic analysis will uncover loci throughout the adult genome which are poised in naïve homeostatic skin but are only expressed and essential in HIF1α-activated situations such as wounding. When compared with epigenetic changes occurring in Hif1a-null embryonic epidermis, I will learn if this poising occurs during embryogenesis and is reliant upon hypoxia. Hif1a has not yet been implicated in epigenetic regulation of the skin, and exploring this function could have important implications for wound healing and disease states of the skin where the protein is again stabilized. The proposed project will be conducted in the lab of Dr. Elaine Fuchs, PhD at the Rockefeller University. The Fuchs lab provides a supportive environment with ample resources to explore the connections between development and inflammation of the skin. Performing the above experiments will establish a robust foundation in cellular and molecular biology techniques with skills in data analysis, critical thinking, leadership, mentorship, and communication, providing strong support for a future independent scientific career in academia.