Project Summary Heart failure is the leading cause of death in the world. At the core of the pathophysiology of heart failure is the inability of the adult mammalian heart to regenerate following injury. In contrast to adults, the newborn mouse heart is capable of complete regeneration following various types of injury, providing a new inroad into possible mechanisms of cardiac regeneration and repair. Previously, we discovered that Nuclear Factor Erythroid-derived 2-related factor 1 (NFE2L1, also known as NRF1) is highly expressed in a regenerative cardiomyocyte population in neonatal mouse hearts. Although NRF1 does not directly promote cardiomyocyte proliferation, it confers strong protection to cardiomyocytes under stress conditions both in vitro and in vivo. Recent studies show that NRF1 regulates proteostasis and redox balance in multiple tissues in response to cellular stress, while its cardiac functions are largely unknown. This proposal outlines a comprehensive plan to further dissect the biological and pathological functions of NRF1 in cardiomyocytes to provide critical insight into the protective mechanism that underlies regeneration and stress adaptation in the heart. In this research plan, Aim 1 will establish how NRF1 protects neonatal cardiomyocytes. Aim 2 will demonstrate the function of NRF1 in mammalian neonatal heart regeneration. Aim 3 will uncover the role of NRF1 as a stress regulator in adult hearts following ischemic injury. In the mentored phase, Aims 1 and 2 will be carried out in the laboratory of the renowned molecular biologist Dr. Eric Olson, and will generate data and mouse knockout models for continued investigation in the independent phase. Aim 3 will be initiated during the K99 phase and continued during the independent phase, dedicated to investigating the therapeutic potential of NRF1 to treat adult ischemic heart disease. In order to gain research independence through mentored training, I will continue to develop expertise in applying transcriptome profiling, including single-nucleus RNA sequencing, to study neonatal heart regeneration (Aims 1 and 2). Such an experience will complement my prior training and constitute an important data generating platform throughout my career. The proposed research requires that I acquire additional mentoring in adult cardiac injury models and related cardiovascular phenotyping (Aim 3). Investigation of NRF1 and its downstream pathways in regulating the stress response of cardiomyocytes during this mentored training will lead to the establishment of an independent niche for my own academic career. In summary, this application will provide me with the scientific training, mentoring, and career development necessary as I transition to independence. Most importantly, the collective body of work generated through the completion of the proposed aims will make major contributions to the field of cardiovascular science.