Sethiya, A. | bioRxiv Science

bioRxiv2026

HIRA-mediated H3.3 deposition preserves hepatocyte cell identity during liver aging

Age-associated functional decline is partly driven by progressive chromatin degeneration. Maintenance of chromatin integrity preserves cell identity and promotes healthy aging, but through different mechanisms in proliferating and non-proliferating cells. However, specific mechanisms of chromatin maintenance and their compensatory capacity in proliferating and non-proliferating cells are undefined. The histone chaperone HIRA deposits the histone variant H3.3 in a DNA replication-independent manner, leading to its accumulation in aging, non-proliferating cells. Here, we show that hepatocyte-specific loss of HIRA causes loss of cell identity, metabolic dysfunction, and accelerated fibrotic pathology with age. Transcriptomic and epigenomic analyses indicate that HIRA-H3.3 preserves chromatin integrity and sustains transcription of highly expressed genes, including cell identity genes. Partial hepatectomy, associated with induced proliferation, restores identity of HIRA knockout livers with compensatory deposition of canonical histones H3.1/2. Together, these results demonstrate that HIRA-mediated H3.3 deposition is essential for safeguarding cell identity and tissue function during aging of non-proliferating cells, but this function can be rescued by tissue regeneration and associated cell proliferation. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=124 SRC="FIGDIR/small/710643v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@a2a26aorg.highwire.dtl.DTLVardef@154e5aeorg.highwire.dtl.DTLVardef@b315a7org.highwire.dtl.DTLVardef@152bca4_HPS_FORMAT_FIGEXP M_FIG C_FIG

genomics↗

bioRxiv2025

Role of GLP1-receptor-mediated α-β-cell communication in functional β-cell heterogeneity.

While islet {beta}-cells were first viewed as a singular functional entity, since the 1970s findings reveal that individual {beta}-cells differ in their insulin secretion. More recently distinct functional subpopulations based on differential calcium dynamics have been demonstrated to drive islet function. Here, we investigate how paracrine signaling, specifically glucagon-like peptide receptor (GLP-1R)-mediated -{beta}-cell communication shapes functional {beta}-cell heterogeneity. To address this, we utilized confocal imaging of calcium responses in isolated islets from GCaMP6s mice and in islets from pancreatic slices of C57BL/6 mice, both before and after a GLP-1R antagonist (exendin-9) treatment. Inhibiting -{beta}-cell communication prolonged response time, increased 1st phase heterogeneity, and decreased the 1st phase response peak. Additionally, it reduced 2nd phase oscillation frequency and heterogeneity, thereby enhancing 2nd phase coordination across {beta}-cells. These changes were more pronounced in -neighboring {beta}-cells. Moreover, addition of exendin-9 disrupted the temporal consistency and -cell proximity of hub-cells and (to a lesser degree) 1st responder {beta}-cells. Together, these findings underscore the importance of engineering islets containing both - and {beta}-cells for stem cellderived islet replacement therapies for Type-1diabetes. Article Highlights{whitebullet} Role of GLP-1R mediated -{beta} cell communication in functional {beta}-cell heterogeneity was unclear. {whitebullet}Does GLP-1R inhibition affect all {beta}-cells uniformly, or will -neighboring cells be affected more? Is existence of 1st responder and hub cell subpopulations shaped by GLP-1R signaling? {whitebullet}GLP-1R inhibition decreases multiple metrics or {beta}-cell responsiveness - especially in -neighboring {beta}-cells. It diminishes spatiotemporal consistency of hub {beta}-cells and (to a lesser degree) 1st responders. {whitebullet}Islet-local GLP-1R communication in absence of exogenous GLP-1 is sufficient for significant control of {beta}-cell function. Incorporating -cells into the engineered islets can improve islet replacement outcomes.

bioengineering↗