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Familial dominant diarrhea caused by an activating GUCY2C mutation is also associated with inflammatory bowel disease

ABSTRACT: BACKGROUND Familial diarrheas are mostly severe recessive diseases. Here we describe the clinical picture and dominant genetic cause of a novel disease in 32 members of a Norwegian family. The chronic diarrhea is of early onset, relatively mild, and is combined with increased susceptibility to intestinal inflammation, ileus and oesophagitis. METHODS Whole genome SNP-analysis was used to identify a single candidate locus for dominant diarrhea on chromosome 12, followed by sequencing of the GU2CY gene. This encodes guanylyl cyclase 2C, an intestinal receptor for bacterial heat-stable enterotoxins and the peptides uroguanylin and guanylin. Functional studies of a missense mutation were performed after heterologous expression of the mutant receptor in HEK293T cells. The therapeutic response to metformin, an inhibitor of the cystic fibrosis transmembrane regulator (CFTR), was investigated in 5 patients. RESULTS We identified heterozygosity for the first described pathogenic human mutation (c.2519G>T ) in the GUCY2C gene. The mutant receptor showed increased cGMP production in response to its ligands. This may cause hyperactivation of the CFTR and consequent increased chloride and water secretion from the enterocytes, resulting in chronic diarrhea. Treatment with the CFTR-inhibitor metformin significantly reduced the frequency of stools in affected individuals by 34-45%. CONCLUSIONS Increased GC-C signaling disturbs normal bowel function, as shown by the diverse symptoms in our patients, and seems to have a pro-inflammatory effect, either through increased Cl- secretion or additional effects of elevated cellular cGMP. The importance of genetic variants in the GC-C-CFTR-pathway for conditions like Crohn’s disease and IBS should be further explored.

ORGANISM(S): Homo sapiens

PROVIDER: GSE31260 | GEO | 2012/04/10

SECONDARY ACCESSION(S): PRJNA144831

REPOSITORIES: GEO

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Project description:BACKGROUND Familial diarrheas are mostly severe recessive diseases. Here we describe the clinical picture and dominant genetic cause of a novel disease in 32 members of a Norwegian family. The chronic diarrhea is of early onset, relatively mild, and is combined with increased susceptibility to intestinal inflammation, ileus and oesophagitis. METHODS Whole genome SNP-analysis was used to identify a single candidate locus for dominant diarrhea on chromosome 12, followed by sequencing of the GU2CY gene. This encodes guanylyl cyclase 2C, an intestinal receptor for bacterial heat-stable enterotoxins and the peptides uroguanylin and guanylin. Functional studies of a missense mutation were performed after heterologous expression of the mutant receptor in HEK293T cells. The therapeutic response to metformin, an inhibitor of the cystic fibrosis transmembrane regulator (CFTR), was investigated in 5 patients. RESULTS We identified heterozygosity for the first described pathogenic human mutation (c.2519G>T ) in the GUCY2C gene. The mutant receptor showed increased cGMP production in response to its ligands. This may cause hyperactivation of the CFTR and consequent increased chloride and water secretion from the enterocytes, resulting in chronic diarrhea. Treatment with the CFTR-inhibitor metformin significantly reduced the frequency of stools in affected individuals by 34-45%. CONCLUSIONS Increased GC-C signaling disturbs normal bowel function, as shown by the diverse symptoms in our patients, and seems to have a pro-inflammatory effect, either through increased Cl- secretion or additional effects of elevated cellular cGMP. The importance of genetic variants in the GC-C-CFTR-pathway for conditions like Crohn’s disease and IBS should be further explored. Linkage analysis was performed (Allegro v 2.0) using Affymetrix 250K SNP arrays according to the manufacturer's directions on DNA extracted from peripheral blood samples. This accession number contains the data for 25 individuals of family branch A in the article.

Project description:Enterotoxigenic Escherichia coli (ETEC) strains that produce both heat-stable (ST) and heat-labile (LT) enterotoxins cause severe post-weaning diarrhea in piglets. However, the relative importance of the individual enterotoxins to the pathogenesis of ETEC infection is poorly understood. In this study, we investigated the effect on virulence of an F4+ ETEC strain when removing some or all of its enterotoxins. Several isogenic mutant strains were constructed that lack the expression of LT in combination with one or both types of ST enterotoxins (STa and/or STb). Host early immune responses induced by these mutant strains 4h after infection were compared to the wild type strain GIS26 Â (O149:F4ac+, Â LT+ Â STa+ Â STb+). At the same time, the immune response of this wild type ETEC strain was compared to the mock-infected control, demonstrating the expression of porcine inflammatory response genes. For these purposes, the small intestinal segment perfusion (SISP) technique and microarray analysis were used and results were validated by qRT-PCR. We also measured net fluid absorption of pig small intestinal mucosa 4h after infection with wild type ETEC, the mutant strains and PBS (mock-infected). These data indicate an important role for STb in inducing small intestinal secretion early after infection. The microarray analysis of the different mutant strains also revealed an important role for STb in ETEC-induced immune response by the significant differential regulation of immune mediators like matrix metalloproteinase 3, interleukin 1 and interleukin 17. We conclude that STb can play a prominent role in ETEC-induced secretion and early immune response. In three pigs, 6 different treatments were performed. These treatments consisted of 4 mutant enterotoxigenic Escherichia coli GIS26 strains, GIS26 wild type strain, or PBS control. Per pig, the small intestine was divided into 6 loops with an interloop in between to avoid cross-contamination. In conclusion, every pig received each of the 6 treatments ad random.

Project description:A mathematical model of the pancreatic duct cell generating high bicarbonate concentrations in pancreatic juice David C Whitcomb, G Bard Ermentrout, Pancreas 2004 29:e30-40; PubMedID:15257112 Abstract: OBJECTIVE: To develop a simple, physiologically based mathematical model of pancreatic duct cell secretion using experimentally derived parameters that generates pancreatic fluid bicarbonate concentrations of >140 mM after CFTR activation. METHODS: A new mathematical model was developed simulating a duct cell within a proximal pancreatic duct and included a sodium-2-bicarbonate cotransporter (NBC) and sodium-potassium pump (NaK pump) on a chloride-impermeable basolateral membrane, CFTR on the luminal membrane with 0.2 to 1 bicarbonate to chloride permeability ratio. Chloride-bicarbonate antiporters (Cl/HCO3 AP) were added or subtracted from the basolateral (APb) and luminal (APl) membranes. The model was integrated over time using XPPAUT. RESULTS: This model predicts robust, NaK pump-dependent bicarbonate secretion with opening of the CFTR, generates and maintains pancreatic fluid secretion with bicarbonate concentrations >140 mM, and returns to basal levels with CFTR closure. Limiting CFTR permeability to bicarbonate, as seen in some CFTR mutations, markedly inhibited pancreatic bicarbonate and fluid secretion. CONCLUSIONS: A simple CFTR-dependent duct cell model can explain active, high-volume, high-concentration bicarbonate secretion in pancreatic juice that reproduces the experimental findings. This model may also provide insight into why CFTR mutations that predominantly affect bicarbonate permeability predispose to pancreatic dysfunction in humans. This SBML version of the model was created directly from the XPPAUT code found in the appendix with the exception of the parameter vr, the ratio between the duct cell volume and the duct lumen, which is defined inversely to the main text in the XPPAUT code. vr was defined as the ratio of the duct cell volume to the duct lumen volume as in the main text. The model reproduces the figures found in the article. The model uses initial assignments for the lumen volume and events to trigger CFTR opening, so only tools supporting these features can be used to simulate it (eg. Copasi and SBW/Roadrunner).

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Familial dominant diarrhea caused by an activating GUCY2C mutation is also associated with inflammatory bowel disease

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