Single pancreatic beta cells co-express multiple islet hormone genes in mice

Abstract

Aims/hypothesisIt is widely accepted that production of insulin, glucagon, somatostatin and pancreatic polypeptide in islet cells is specific to beta, alpha, delta and pancreatic polypeptide cells, respectively. We examined whether beta cells express other genes encoding islet hormones.MethodsNested RT-PCR was performed on single beta cells of transgenic mice with green fluorescent protein (GFP) driven by mouse insulin I promoter (MIP-GFP).ResultsOnly 55% of adult beta cells expressed the insulin gene alone, while others expressed two or more islet hormone genes; 4% expressed all four hormone genes. In embryonic and neonatal cells, 60% to 80% of GFP+ cells co-expressed pancreatic polypeptide and insulin genes in contrast to 29% in adult. To clarify cell fate, we conducted lineage tracing using rat insulin II promoter-cre mice crossed with reporter mice Gt(ROSA)26Sor-loxP-flanked STOP-cassette-GFP. All GFP+ cells expressed insulin I and II genes, and showed similar heterogeneity of co-expression to that seen in MIP-GFP mice. Although we report expression of other hormone genes in a significant proportion of beta cells, our lineage tracing results demonstrate that after inducing InsII (also known as Ins2) expression, beta cell progenitors do not redifferentiate to non-beta cells.Conclusions/interpretationThis study shows co-expression of multiple hormone genes in beta cells of adult mice as well as in embryos and neonates. This finding could: (1) represent residual expression from beta cell precursors; (2) result from alternative developmental pathways for beta cells; or (3) denote the differentiation potential of these cells. It may be linked to functional heterogeneity. This heterogeneity in gene expression may provide a means to characterise the functional, cellular and developmental heterogeneity seen in beta cells.Electronic supplementary materialThe online version of this article (doi:10.1007/s00125-009-1570-x) contains supplementary material, which is available to authorised users.

Use of the Fluidigm C1 platform for RNA sequencing of single mouse pancreatic islet cells

“…These double-hormonepositive cells are unlikely to be artifacts arising from the cell isolation procedure because they were also observed in intact islets in pancreas sections using RNA FISH and immunofluorescence staining. It is important to emphasize that islet cells do express very low levels (0.003-0.3%) of other endocrine hormones, consistent with a previous study (18). This could reflect low-level contamination, but if real the functional significance remains to be determined.…”

Kinetics and genomic profiling of adult human and mouse β-cell maturation

“…It has been shown that insulin-expressing β-cells in adults co-express several combinations of endocrine hormones. 19,20 It is possible that some adult islet cells may retain plasticity and have the potential to revert back to a fetal-like state where multiple hormones are expressed in individual cells, perhaps under conditions of stress, such as diabetes. 21 Characterizing the plasticity of adult β-cells has important implications for β-cell regeneration and in vitro generation of functional β-cells.…”

Subpopulations of GFP-Marked Mouse Pancreatic β-Cells Differ in Size, Granularity, and Insulin Secretion

“…All samples were analyzed on a MoFlo cell sorter with Summit software (Cytomation, Fort Collins, CO) as previously described (11). For analysis of islet cells from MIP-GFP mice, the GFP signal was so strong that a neutral density filter was used to reduce brightness.…”

“…The introduction of this transgene does not appear to be deleterious, because these mice have normal pancreatic development, glucose tolerance, islet histology, and ␤-cell secretory function (13). Our previous analysis of single GFP-positive cells from these mice with nested PCR revealed that only 55% of the ␤-cells expressed the insulin gene alone and 4% of the cells expressed genes of four islet hormones (insulin, glucagon, somatostatin, and pancreatic polypeptide) (11,12). Another example of heterogeneity in adult ␤-cells was shown with a dual-reporter construct (Pdx1-monomeric red fluorescent protein/insulin-enhanced GFP dual-reporter lentivirus) (14).…”

“…Moreover, we and others have found heterogeneity in sorted single ␤-cells with regard to very low expression of mRNA of the hormone products of other islet cell types (11,12). Our study used sorted ␤-cells from transgenic mice expressing green fluorescent protein (GFP) under the control of the mouse insulin I gene promoter (MIP) (13).…”