In summary, we have developed a highly reproducible protocol to generate iPSC-derived hematopoietic progenitor cells and microglia-like cells in high yield that can be used in functional assays to interrogate microglia function. We have also identified a commercial HPC source that can be readily differentiated to iMGLs with our protocol to study microglia biology. We demonstrate that iMGLs phagocytose a variety of neuronal substrates including beta-amyloid, brain-derived tau oligomers, and human synaptosomes that can be used to study the influence of AD genetic risk factors, including recently identified novel TREM2 variants (Sirkis et al., 2016) on microglia function, with the potential to uncover altered microglia pathways that can guide future therapeutic targets. Because many AD-GWAS genes also suggest microglia-neuronal crosstalk (e.g. TREM2-Lipids and APOE/J, CD33-Sialic Acid, MS4A cluster/Lipids), we demonstrated that iMGLs can be studied in context with neurons and glia by examining how both rodent and human neuronal cells influence microglia phenotype and function, both in vitro and in vivo. As expected, iMGLs gene profiles shift toward a neuronal-centric phenotype and respond appropriately to injury in 3D cell culture
