Stress tolerant annual killifish: a new model for the cellular stress response

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Project Summary/Abstract When faced with environmental stress, cells and organisms must conserve resources by decreasing global translation and simultaneously upregulating stress-responsive genes. How cells do this has eluded researchers yet promises insight into basic cell biology and novel therapeutics. This proposal takes an innovative approach to the problem by developing a naturally stress-tolerant fish as a model for the cellular stress response and using it to examine the contribution of membraneless organelles (in particular stress granules (SGs)) and small non-coding RNAs (ncRNAs) to gene expression regulation and stress tolerance. SGs are highly conserved stress-induced assemblies of RNA and protein which may regulate gene expression by selective sequestration of RNAs and proteins, however their function remains unknown. Small ncRNAs, such as microRNAs, can regulate the gene expression of particular mRNAs by preventing their translation into protein, yet identifying adaptive ncRNAs that function in the stress response remains challenging. The annual killifish Austrofundulus limnaeus inhabits temporary ponds in Venezuela that expose developing fish embryos to harsh environmental conditions, including anoxia. A. limnaeus embryos can survive over 100 days without oxygen and cells derived from A. limnaeus embryos can survive two weeks without oxygen. A. limnaeus display unique SG and ncRNA biology. Our preliminary data show that A. limnaeus cells treated with sodium arsenite do not form SGs, but still shut down translation. This surprising finding suggests that SG avoidance may be adaptive and support anoxia tolerance in killifish cells. Small ncRNA studies in anoxia-tolerant vertebrates identified mitochondria-derived small ncRNAs (mitosRNAs) as putative regulators of gene expression driving anoxia-induced metabolic depression in A. limnaeus embryos. These mitosRNAs may therefore underpin organismal anoxia tolerance and represent a novel stress response mechanism. This proposal will address the following questions: 1. How do killifish cells decouple translation inhibition from stress granule formation?; 2. How do mitosRNAs regulate protein synthesis under stress?; and 3. How do SG avoidance and mitosRNA expression support anoxia tolerance? Understanding the mechanism and consequences of these cellular phenomena will offer unique insight into fundamental cell biology that may inform treatments for heart attack and stroke, as well as mitochondrial and neurodegenerative diseases. This proposal will facilitate the career development and transition to independence of a female scientist committed to promoting and supporting diversity in STEM. The mentored phase will be conducted in the rich training environment of Brigham and Women’s Hospital/Harvard Medical School to facilitate her career development. Transitioning to independence will poise her to advance inclusive excellence in higher education and STEM, including fostering the success of diverse trainees her in lab.