lncRNA Glelr modulates microglia inflammatory programs in association with PU.1.

Abstract

Long non-coding RNAs (lncRNAs) are emerging as key regulators of brain function, but their contribution to microglial aging and neurodegenerative disease remains largely unknown. Because only 1.5% of the human genome encodes proteins, whereas the vast majority of transcripts belong to the largely unexplored non-coding RNAome, elucidating the functions of non-coding RNAs provides an unprecedented opportunity to expand the space for therapeutic discovery. We recently identified the glia-enriched lncRNA Glelr as upregulated in the aging mouse hippocampus. Here, we investigated its function in microglia and its human homolog GLELR. We found that Glelr/GLELR is expressed in both astrocytes and microglia and increases with age. Knockdown of Glelr in primary microglia led to enhanced expression of pro-inflammatory cytokines, including TNFα, and increased phagocytic activity. RNA-sequencing revealed widespread transcriptional changes enriched for TNF and complement signaling pathways. The human homolog GLELR showed conserved functions in iPSC-derived microglia, where its loss similarly promoted inflammatory gene expression and phagocytosis. Mechanistically, Glelr interacts with the microglial transcription factor PU.1, and its depletion overlapped with PU.1-driven transcriptional programs. Consistent with these findings, GLELR expression was significantly reduced in postmortem Alzheimer's disease (AD) brains, and AD-associated genes were enriched among Glelr-regulated targets. Together, our results identify Glelr/GLELR as a conserved, aging-associated lncRNA that modulates microglial inflammatory states through interaction with PU.1. This work links glial lncRNA regulation to AD-related neuroinflammation and suggests GLELR as a potential molecular target to fine-tune microglial activity in neurodegenerative diseases.