How cells preserve a stable identity and functional specificity in the face of dynamic environmental and metabolic signals remains a fundamental biological question. Dendritic cell (DC) functional specialisations are thought to reflect an integration of cell-intrinsic lineage imprinting and extrinsic environmental stimuli, but how these signals are integrated and maintained is poorly understood.

O‑GlcNAcylation is an evolutionarily conserved, nutrient‑sensing post‑translational modification that dynamically regulates nucleocytosolic proteins and is therefore well positioned to link local environmental cues with maintaining cell identity. Using DC‑specific ablation of O‑GlcNAc transferase (OGT) or O‑GlcNAcase (OGA), we show that loss of O‑GlcNAcylation leads to profound, tissue‑ and subset‑specific disruptions in DC development and function, identifying this modification as a key regulator of DC biology.

Proteomic profiling revealed that approximately 20% of O‑GlcNAcylated nucleocytosolic proteins in DCs are epigenetic regulators. Consistent with this, single‑cell RNA‑seq and ATAC‑seq analyses of wild‑type and OGT‑deficient DC subsets uncovered extensive, subset‑specific changes in gene expression and chromatin accessibility. For instance, OGT-deficient cDC2A (SIRPα⁺ESAM⁺ DTX1⁺ CLEC12A⁻ CX3CR1⁻) displayed marked transcriptional reprogramming, with 59% of genes upregulated in OGT‑deficient cDC2A normally characteristic of the cDC2B subset. These included FCGR2B and CD209A, canonical surface markers of the cDC2B or monocyte-derived DC3s lineages. The transcriptional alterations found in OGT-deficient DC were accompanied with marked functional changes. Splenic cDC2A cells are key inducers of T-follicular helper (Tfh) and germinal centre B-cell (GCBC) responses, but despite reduced numbers of cDC2As in DC‑specific OGT‑deficient mice,  immunisation with OVA paradoxically resultd in increased Tfh cells, GCBCs, and antigen‑specific antibody responses.

Our results demonstrate that O‑GlcNAcylation stabilises developmentally imprinted DC identity by regulating epigenetic control of transcription in a tissue‑ and subset‑specific manner. The molecular mechanisms underlying O‑GlcNAcylation‑dependent regulation of transcriptional stability in DCs will be discussed further in this presentation.