B2m role in the crosstalk between macrophages and HSPCs and its impact on hematopoietic clonality

• Grant number: 23/04482-1
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: July 20, 2023
• End date: July 19, 2024
• Field of knowledge: Biological Sciences - Immunology - Cellular Immunology
• Principal Investigator: Niels Olsen Saraiva Câmara
• Grantee: Lais Cavalieri Paredes
• Supervisor: Leonard Zon
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Boston Children's Hospital, United States
• Associated to the scholarship: 20/10263-2 - Role of histones deacetylases in regeneration and macrophage polarization in post-inducing acute kidney injury in Zebrafish (Danio rerio), BP.DR

Abstract

Recent studies have demonstrated the involvement of embryonic macrophages in the regulation of the number of hematopoietic clones. A macrophage may completely engulf a stem cell ("dooming") or it may capture parts of the HSPCs cellular material ("grooming"). In the latter situation, the stem cell goes on to divide. This interaction is mediated by the "eat me" signal calreticulin (CALR) on the surface of HSPCs. Macrophage depletion led to a reduction of the number of HSPC clones in the adult marrow, suggesting that a quality assurance mechanism for stem cells is operative. However, the molecular cues regulating the "dooming" versus "grooming" behavior remain elusive. We hypothesized that a "don't eat-me" signal may counterbalance the "eat-me" signal provided by CALR, thus regulating macrophage behavior. Our project aims to investigate the role of b2-microglobulin (B2m), a "don't eat-me" molecule, in the interaction between macrophages and HSCs and evaluate its impact on the HSC clones' balance. We plan to use zebrafish as a model organism of transgenic lines that allow us to evaluate by fluorescence microscopy the interaction between the two cell types and the number of clones established after manipulating the expression levels of molecules involved in the process. To evaluate the diversity of clones after modulation of B2m expression, we will employ the TWISTR system, which combines mosaic CRISPR-Cas9 mutagenesis with color labeling of HSPC clones, allowing the clonal quantification and cell sorting for further deep sequencing assays. This study will have direct implications for blood diseases, transplantation, and the regulation of stem cells in other tissues by reprograming the macrophage behavior. (AU)