Biology subjects

Lund, P.-E.

Publications and source records attributed to Lund, P.-E..

3 recordsLinked to original sources

bioRxiv2023

RFX6 haploinsufficiency predisposes to diabetes through impaired beta cell functionality

Regulatory factor X 6 (RFX6) is indispensable for pancreatic endocrine development and differentiation. The RFX6 protein-truncating variant p.His293LeufsTer7 is significantly enriched in the Finnish population with almost 1:250 individuals as a carrier. Importantly, the FinnGen study indicates a high predisposition for heterozygous carriers to develop type 2 diabetes (T2D) and gestational diabetes. To understand the role of this variant in {beta}-cell development and function, we generated allelic series of isogenic pluripotent stem cell models and directed them into pancreatic islet lineages (SC-islets). Expectedly, in-vitro models of the homozygous RFX6-/- variant failed to generate pancreatic endocrine cells, recapitulating the phenotype in Mitchell-Riley syndrome. Notably, heterozygous RFX6+/- derived SC-islets showed reduced {beta}-cell maturation markers and calcium oscillations, resulting in defective insulin secretion, without affecting {beta}-cell number or insulin content. The reduced insulin secretion is sustained during in-vivo implantation studies, consistent with the susceptibility of the carriers to develop diabetes. TeaserModeling RFX6-assocciated neonatal and type-2 diabetes using allelic series stem cell-derived islets in-vitro and in-vivo.

cell biology↗

bioRxiv2021

Functional, metabolic and transcriptional maturation of stem cell derived beta cells

Transplantation of pancreatic islet cells derived from human pluripotent stem cells is a promising treatment for diabetes. Despite progress in stem cell-derived islet (SC-islet) generation, detailed characterization of their functional properties has not been conducted. Here, we generated functionally mature SC-islets using an optimized protocol and comprehensively benchmarked them against primary adult islets. Biphasic glucose stimulated insulin secretion developed during in vitro maturation, associated with cytoarchitectural reorganization and increased alpha cells. Electrophysiology and exocytosis of SC-islets were comparable to adult islets. Glucose-responsive insulin secretion was achieved despite differences in glycolytic and mitochondrial glucose metabolism. Single-cell transcriptomics of SC-islets in vitro and throughout 6 months of murine engraftment revealed a continuous maturation trajectory culminating in a transcriptional landscape closely resembling that of primary islets. Our thorough evaluation of SC-islet maturation highlights their advanced degree of functionality and supports their use in further efforts to understand and combat diabetes.

developmental biology↗

bioRxiv2019

Paracrine control of α-cell glucagon exocytosis is compromised in human type-2 diabetes

Glucagon is secreted from pancreatic -cells to activate gluconeogenesis and other pathways that raise blood glucose during hypoglycemia. Glucose-dependent regulation of glucagon secretion involves both -cell-intrinsic mechanisms and paracrine control through insulin and somatostatin. In type-2 diabetes (T2D) inadequately high glucagon levels contribute to hyperglycemia. To understand these disease-associated changes at the cellular level, and to isolate intrinsic and paracrine effects, we analyzed glucagon granule exocytosis and membrane excitability in isolated -cells from 56 non-diabetic (ND) and 15 T2D human donors. High resolution imaging showed that glucagon granule exocytosis had a U-shaped sensitivity to glucose, with the slowest rate around 7 mM glucose, and accelerated rates at <5 and >10 mM glucose. Exocytosis was reduced in T2D -cells, but their glucose sensitivity remained intact and there were no changes in voltage-dependent ion currents or granule trafficking. Instead, -cells from T2D donors were markedly insensitive to somatostatin and insulin, which rapidly inhibited exocytosis and electrical activity in ND cells. Thus, intrinsic mechanisms do not inhibit glucagon secretion at hyperglycemia, and elevated glucagon levels in human T2D reflect an insensitivity of -cells to paracrine inhibition.

cell biology↗