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Principal Investigator: John Andrew Pospisilik
Organization: VAN ANDEL RESEARCH INSTITUTE
Fiscal Year: 2024
Award: $698,646
Funding agency: National Institute of Diabetes and Digestive and Kidney Diseases
PROJECT SUMMARY
Type 2 diabetes (T2D) is a disease that results from relative pancreatic β-cell dysfunction, and affects >400
million people. We (Rutter) previously identified functional β-cell subsets based upon analysis of real-time Ca2+
responses and cell-cell connectivity. A “βLEADER” population (~5% of β-cells) exhibits fast and robust Ca2+ influx
that controls the timing of islet-wide glucose responses, and a separate population of highly interconnected βHUB
-cells (5-10% of β-cells) that synchronizes glucose responses, islet-wide. More recently, we (Pospisilik)
discovered that H3K27me3 dosage is a novel regulator of β-cell lineage differentiation, stability, and functional
specification. We identified two epigenetically distinct β-cell populations (βHI and βLO) that are conserved across
mice and humans and comprise >90% of the β-cell compartment. They are distinguished by distinct nuclear and
cell surface protein expression, by distinct epigenomes and transcriptomes, and by a series of morphological
and functional differences. Importantly, βHI and βLO cells can be purified by FACS, and their relative ratios are
altered in mouse models and human T2D. Our preliminary data now suggest that βLEADER and βHUB cells together
comprise the epigenetically-defined βHI cells, and that βFOLLOWER cells are synonymous with βLO cells. The
objective of this project is to test this hypothesis, and define the functional and disease relevance of these
putative β-cell subtypes. In Aim 1, we will use novel single-cell epigenomic tools to determine the extent to which
functionally- and epigenetically-defined β-cell subsets are the same. In Aim 2, we will use conditional deletion
mouse models to determine when and how H3K27me3 levels control the emergence of each β-cell subset, and
their relative ratios. In Aim 3, we will use the same mouse models to determine if and how β-cell subtype ratios
relate to obesity-associated diabetes, and if subtype proportions can be reversed by diet, SGLT2i, or GLP1R
agonist treatments. We will perform parallel studies in human SC-islets to determine if HNF1A mutants (a causal
T2D genetic variant) alter β-cell subtype ratio and function, and if those effects are reversible. Finally, we will
screen biobanked nPOD and ADI pancreatic samples for the relative proportions of these functional subsets
across metabolic diseases. Thus, Aim 3 will establish the extent and impact of subtype-specific β-cell dysfunction
in T2D. By using this unified theoretical and experimental framework, we will establish an epigenetic basis for
understanding and manipulating putative β-cell subtype number and function in vitro and in vivo, and novel
methods for generating SC-islets with preferential skews in β-cell subtypes.
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