Alzheimer's disease-associated PLCG2 variants alter microglial state and function in human iPSC-derived microglia-like cells

BACKGROUND: Variants of PLCG2, a key microglial immune signaling protein, are genetically linked to Alzheimer's disease (AD) risk. Understanding how PLCG2 variants alter microglial function is critical for identifying mechanisms that drive neurodegeneration or resiliency in AD. METHODS: iPSC-derived microglia carrying the protective PLCG2P522R or risk-conferring PLCG2M28L variants, or loss of PLCG2, were generated to ascertain the impact on microglial transcriptome and function. RESULTS: Protective PLCG2P522R microglia showed significant transcriptomic similarity to isogenic controls. In contrast, risk-conferring PLCG2M28L microglia shared similarities with PLCG2KO microglia, with functionally reduced TREM2 expression, blunted inflammatory responses, and increased proliferation and cell death. Uniquely, PLCG2P522R microglia showed elevated cytokine secretion after LPS stimulation and were protected from apoptosis. DISCUSSION: These findings demonstrate that PLCG2 variants drive distinct microglia transcriptomes that influence microglial functional responses that could contribute to AD risk and protection. Targeting PLCG2-mediated signaling may represent a powerful therapeutic strategy to modulate neuroinflammation. Overall design: RNA-seq profiling of basal iPSC derived microglia-like cells homozygous for WT, P522R, M28L, or KO PLCG2.