MEF2C controls lysosomal and lipid clearance programs linked to Alzheimer’s disease risk in macrophages [bulkRNAseq_WTC11_iMGL]

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, 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 AD causal variants in other loci to MEF2C-regulated regulatory regions and downstream risk genes. 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 mechanism to modulate AD-relevant pathology.