lncRNA 3222401L13Rik / ENSG00000272070 modulates microglial inflammatory programs in association with PU.1

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 3222401L13Rik as upregulated in the aging mouse hippocampus. Here, we investigated its function in microglia and its human homolog ENSG00000272070 . We found that 3222401L13Rik is expressed in both astrocytes and microglia and increases with age. Knockdown of 3222401L13Rik 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 ENSG00000272070 showed conserved functions in iPSC-derived microglia, where its loss similarly promoted inflammatory gene expression and phagocytosis. Mechanistically, 3222401L13Rik interacts with the microglial transcription factor PU.1, and its depletion overlapped with PU.1-driven transcriptional programs. Consistent with these findings, ENSG00000272070 expression was significantly reduced in postmortem Alzheimer’s disease (AD) brains, and AD-associated genes were enriched among 3222401L13Rik -regulated targets. Together, our results identify 3222401L13Rik / ENSG00000272070 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 3222401L13Rik as a potential molecular target to fine-tune microglial activity in neurodegenerative diseases.