DNA methylation Dependent Restriction of Tyrosine Hydroxylase Contributes to Pancreatic β-cell Heterogeneity

Abstract

The molecular and functional heterogeneity of pancreatic β-cells is well recognized. Pancreatic islets harbor a small subset of β-cells that co-express Tyrosine Hydroxylase (TH), an enzyme involved in synthesis of catecholamines that repress insulin secretion. Restriction of this sub-population within islets is essential for appropriate insulin secretion. However, the distinguishing characteristics of this subpopulation and the mechanisms that restrict TH expression in β-cells are not known. Here, we define the specific molecular and metabolic characteristics of the TH+ β-cells and show that TH expression in β-cells is restricted by DNA methylation patterning during β-cell lineage specification. Ablation of de novo DNA methyltransferase Dnmt3a in the pancreatic- and endocrine-progenitor lineages results in a dramatic increase in the proportion of TH+ β-cells, while β-cell specific ablation of Dnmt3a has no effect on this sub-population. We demonstrate that maintenance of Th promoter DNA methylation patterns is essential for its continued restriction in postnatal β-cells, and that loss of DNA methylation dysregulates TH expression in β-cells in response to chronic overnutrition, contributing to impairment of β-cell identity. These data highlight the essential requirement of DNA methylation patterning in regulating endocrine cell fates, and reveal a novel role of DNA methylation in β-cell heterogeneity.

Islet cilia and glucose homeostasis

“…These include receptors for locally secreted neurotransmitters and endocrine hormones. β-cells produce in addition to insulin several neurotransmitters including serotonin (5-HT) and γ-aminobutyric acid (GABA) ( Almaça et al, 2016 ; Arrojo E Drigo et al, 2019 ; Huising, 2020 ; Parveen et al, 2022 ). 5-HT is packaged in insulin vesicles for co-release with insulin and promotes glucose clearance in the islet via stimulation of insulin and inhibition of glucagon release ( Bennet et al, 2015 ; Almaça et al, 2016 ).…”