Investigating stem and progenitor cell quality assurance in development andregeneration. - PROJECT SUMMARY/ABSTRACT Macrophages are a highly dynamic population capable of modulating stem/progenitor cells during early development and in regeneration. A general role for immune cells in mediating the inflammatory milieu has long been appreciated, but more recent efforts have uncovered more direct cell-cell communication between macrophages and stem cells which regulate their quiescence, migration, proliferation, and differentiation. Improvements in clonal lineage analysis, single cell sequencing, and live imaging have facilitated discovery of transient macrophage-stem cell interactions with long-term consequences. Through selective amplification of individual stem/progenitor cells and phagocytosis of others, macrophages can effectively ‘quality assure’ overall tissue function and architecture during development and regeneration. The overall goals of my lab are to dissect the molecular signals which mark stem/progenitor cells for macrophage interaction at the transcriptional, proteomic, and metabolic levels, to compare regulatory cues delivered by macrophages in development and regeneration across multiple tissue types, and to uncover the mechanisms which lead to elimination of some stem cells and expansion of others. Understanding this biology will allow for the development of therapeutic approaches using macrophages to specifically eliminate disease-causing cells while also providing supportive cues to others. Over the next five years, my group will develop a technical approach that combines molecular profiling, clonal analysis, live imaging, and zebrafish genetics to study stem cell quality assurance by macrophages. We will utilize sophisticated genetic approaches to study the presentation of the ‘eat me’ signal Calreticulin which mediate macrophage-stem cell interactions in developing and regenerating blood, skeletal muscle, and spinal cord. We will compare the influence of macrophages on the architecture of these organ systems through clonal barcoding, single cell ATAC-sequencing, and live- imaging approaches to identify the shared functional and genomic features at play. Finally, we will utilize cutting edge single cell proteomics and CRISPR mutagenesis to discover pathways which modulate macrophage engulfment of stem/progenitor cells in development and regeneration of the blood and spinal cord. Together these approaches will advance a mechanistic understanding of macrophages as key modulators of stem cells in development and regeneration. We are broadly interested in questions concerning cell-cell competition, non-cell autonomous stem cell regulation, and regeneration versus scarring. By leveraging the advantages of zebrafish, we will address these questions by studying the interface between macrophages and stem/progenitor cells across multiple organ systems. The long-term goal of this project is to develop strategies for both targeted elimination of specific cells – such as in scar formation or cancer – and targeted protection or expansion of other cells – such as after injury or transplantation.
