SUN-146 Do highly-connected beta cell hubs overlap with epigenetically-defined BetaHi cells?

Abstract G. Ostinelli: None. P. Carapeto: None. Z. Kabbash: None. E. Dror: None. J. Pospsisilik: None. G.A. Rutter: None. The adult beta cell is highly specialized and long-lived, and deploys epigenetic control to maintain its stability over time. These mechanisms may also be important to achieve beta cell heterogeneity, which is important to ensure normal glucose-stimulated insulin release. Recent work has described “Beta Hi” and “Beta Lo” populations defined by increased or decreased trimethylation, respectively, on lysine 27 of histone 3 (H3K27 me3). “Beta Hi” cells are also characterized by higher nuclear compaction, insulin content and release, as well as an increased number of mitochondria compared to “Beta Lo” cells. Interestingly, the two subgroups differ in terms of the expression of the cell surface marker CD24, with “Beta Hi” cells enriched for the latter. The extent to which these sub-groups may align with beta cell function, and their ability to coordinate calcium waves dictating insulin secretion, is unclear. In particular, whether subpopulations from which calcium oscillations emanate (“leaders”) or are coordinated (“hubs”) present an enrichment for CD24 is still unknown. Our objective here was to determine whether, and to what extent, CD24+ cells (“Beta Hi”), overlap with highly-connected “hub” cells. In order to do this, islets were isolated from Ins-Cre:GCaMP6LoxP mice and then transfected with an adenovirus expressing Photo Activatable (PA)-mCherry. Calcium waves were recorded by confocal imaging (Zeiss Airyscan) and analysed using ImageJ and MATLAB. Hubs were identified and labelled by photoexcitation of PA-mCherry. Islets were then fixed, and immunostaining performed to identify CD24+ cells. Our findings suggest that hubs cells display an enrichment of CD24 compared to followers, suggesting that hubs may belong to the “Beta Hi” subpopulation. Future studies will be needed to assess to which sub-population “leader” cells belong, and whether these assignations are altered in models of type 2 diabetes. Sunday, June 2, 2024