TRPM7 is a critical regulator of pancreatic endocrine development and high-fat diet-induced β-cell proliferation.

The melastatin subfamily of the transient receptor potential channels (TRPM) are regulators of pancreatic {beta}-cell function. TRPM7 is the most abundant islet TRPM channel; however, the role of TRPM7 in {beta}-cell function has not been determined. Here, we utilized various spatiotemporal transgenic mouse models to investigate how TRPM7 knockout influences pancreatic endocrine development, proliferation, and function. Ablation of TRPM7 within pancreatic progenitors reduced pancreatic size, as well as -cell and {beta}-cell mass. This resulted in impaired glucose tolerance due to decreased serum insulin levels. However, ablation of TRPM7 following endocrine specification or in adult mice did not impact endocrine expansion or glucose tolerance. As TRPM7 regulates cell proliferation, we assessed how TRPM7 influences {beta}-cell hyperplasia under insulin resistant conditions. {beta}-cell proliferation induced by high-fat diet was significantly decreased in TRPM7 deficient {beta}-cells. The endocrine roles of TRPM7 may be influenced by cation flux through the channel, and indeed we find that TRPM7 ablation alters {beta}-cell intracellular Mg2+. Together, these findings reveal that TRPM7 controls pancreatic progenitor expansion and {beta}-cell proliferation, which is likely due to regulation of Mg2+ homeostasis. SummaryThis manuscript identifies a critical developmental role for TRPM7 channels in pancreatic progenitor cells. The manuscript also determines that TRPM7 plays a key role in {beta}-cell proliferation under insulin-resistant conditions.