Differential CpG methylation atNnatin the early establishment of beta cell heterogeneity

Abstract

Beta cells within the pancreatic islet represent a heterogenous population wherein individual sub-groups of cells make distinct contributions to the overall control of insulin secretion. The molecular mechanisms through which beta cell hierarchy is established remain poorly understood. The neuronatin (Nnat) gene is imprinted in mice and humans and is required for normal insulin synthesis and secretion. Here, we demonstrate that Nnat is differentially expressed in a discrete beta cell population in a developmental-stage and DNA methylation (DNMT3A)-dependent manner. Explored in mice expressing eGFP from a bacterial artificial chromosome-expressed transgene, NNAT+cells displayed a discrete transcriptome, and appear to represent a beta cell population specialised for insulin production. Correspondingly, highly connected hub cells were less abundant in the NNAT+population. These findings demonstrate that differential DNA methylation at Nnat represents a novel means through which beta cell heterogeneity is established.

Developmentally dynamic changes in DNA methylation in the human pancreas

“…NNAT is an imprinted proteolipid-encoding gene expressed specifically from the paternal allele that is highly expressed within differentiating endocrine cells and immature aggregating islet cells in mice (29, 30). Of note, a recent study showed that the mouse Nnat gene is differentially expressed across development in a discrete population of beta cells, and that this transcriptional plasticity is directly regulated by DNA methylation (31). The top hypomethylated dDMR (chr19: 16830287-16830859, 9 sites, P = < 1.14 x 10 -304 , Figure 2E ) spans the transcription start site (TSS) of the gene encoding WD repeat domain-containing protein 1 ( NWD1 ), which plays an important role in the developmental regulation of gene expression (32).…”

An inter-organelle contact between endosomal GLP-1R, ER VAP-B, and the mitochondrial AKAP SPHKAP triggers PKA-dependent MIC19 phosphorylation and β-cell mitochondrial remodelling

“…Supernatants were subsequently acidified with 0.5% trifluoroacetic acid (TFA), followed by desalting using reversed-phase spin tips (Glygen Corp) and dried using vacuum centrifugation. Dried peptides were resuspended in 0.1% TFA and Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS) performed as previously described 65 using an Ultimate 3000 nano-HPLC coupled to a Q-Exactive mass spectrometer (Thermo Scientific) via an EASY-Spray source. Peptides were loaded onto a trap column (Acclaim PepMap 100 C18, 100 μm × 2 cm) at 8 μl/min in 2% acetonitrile, 0.1% TFA.…”

Developmentally dynamic changes in DNA methylation in the human pancreas

“…NNAT is an imprinted proteolipid-encoding gene expressed specifically from the paternal allele that is highly expressed within differentiating endocrine cells and immature aggregating islet cells in mice [30,31]. Of note, a recent study showed that the mouse Nnat gene is differentially expressed across development in a discrete population of beta cells, and that this transcriptional plasticity is directly regulated by DNA methylation [32]. The top hypomethylated dDMR (chr19: 16,830,287-16830859, 9 sites, P = < 1.14 × 10 -304 , Fig.…”