MEF2C controls lysosomal and lipid clearance programs linked to Alzheimer’s disease risk in macrophages

Risk alleles for late-onset Alzheimer’s disease (AD) are enriched in myeloid cis-regulatory elements, implicating myeloid gene-regulatory networks in disease susceptibility. A conserved lipid-associated transcriptional signature—spanning disease-associated microglia and peripheral lipid-associated macrophages (DLAM)—emerges across neurodegenerative and metabolic diseases characterized by lipid overload, yet the transcriptional regulators of this gene expression program remain incompletely defined. Here, we show that MEF2C—a candidate AD risk gene—is a master DLAM regulator. Using MEF2C knockout and knockdown in human iPSC-derived microglia and macrophages, we found that total or partial MEF2C loss is sufficient to induce DLAM-associated transcriptional, epigenomic, and functional remodeling, including enhanced lysosomal activity and cholesterol efflux. Integration of chromatin accessibility and regulatory epigenetic profiles with functionally informed fine-mapping linked candidate causal variants in AD risk loci to MEF2C-regulated cis-regulatory elements that target candidate AD risk genes at these loci. In a triculture model of AD, microglial MEF2C loss is associated with an increased DLAM population and a reduced Aβ42/40 ratio, supporting context-dependent reprogramming of microglia as a potential biological mechanism to modulate AD-relevant pathology.