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Novel GUCY2C variant causing familial diarrhea in a Mennonite kindred and a potential therapeutic approach.

ABSTRACT: Guanylate cyclase 2C (GC-C), encoded by the GUCY2C gene, is implicated in hereditary early onset chronic diarrhea. Several families with chronic diarrhea symptoms have been identified with autosomal dominant, gain-of-function mutations in GUCY2C. We have identified a Mennonite patient with a novel GUCY2C variant (c.2381A > T; p.Asp794Val) with chronic diarrhea and an extensive maternal family history of chronic diarrhea and bowel dilatation. Functional studies including co-segregation analysis showed that all family members who were heterozygous for this variant had GI-related symptoms. HEK-293 T cells expressing the Asp794Val GC-C variant showed increased cGMP production when stimulated with Escherichia coli heat-stable enterotoxin STp (HST), which was reversed when 5-(3-Bromophenyl)-5,11-dihydro-1,3-dimethyl-1H-indeno[2',1':5,6]pyrido[2,3-d]pyrimidine-2,4,6(3H)-trione (BPIPP; a GC-C inhibitor) was used. In addition, cystic fibrosis transmembrane conductance regulator (CFTR) activity measured with SPQ fluorescence assay was increased in these cells after treatment with HST, indicating a crucial role for CFTR activity in the pathogenesis of this disorder. These results support pathogenicity of the GC-C Asp794Val variant as a cause of chronic diarrhea in this family. Furthermore, this work identifies potential candidate drug, GC-C inhibitor BPIPP, to treat diarrhea caused by this syndrome.

SUBMITTER: Wolfe RM

PROVIDER: S-EPMC8251925 | biostudies-literature |

REPOSITORIES: biostudies-literature

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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.

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Novel GUCY2C variant causing familial diarrhea in a Mennonite kindred and a potential therapeutic approach.

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