Citations

ABSTRACT The Ca 2+ ‐activated Cl − channel, anoctamin 1 (Ano1, also known as transmembrane protein 16A) contributes to intestinal pacemaking, fluid secretion, cellular excitability, and tissue development. The human ANO1 promoter contains binding sites for the glioma‐associated oncogene (Gli) proteins. We investigated regulation of ANO1 transcription by Gli. ANO1 promoter activity was determined using a luciferase reporter system. Binding and functional effects of Glis on ANO1 transcription and expression were demonstrated by chromatin immunoprecipitation, small interfering RNA knockdown, PCR, immunolabeling, and recordings of Ca 2+ ‐activated Cl − currents in human embryonic kidney 293 (HEK293) cells. Results from previous genome‐wide association studies were used to test ANO1 promoter polymorphisms for association with disease. Gli1 and Gli2 bound to the promoter and repressed ANO1 transcription. Repression depended on Gli binding to a site close to the ANO1 transcriptional start site. Mutation of this site prevented Gli binding and transcriptional repression. Knockdown of Gli expression and inhibition of Gli activity increased expression of ANO1 RNA and Ca 2+ ‐activated Cl − currents in HEK293 cells. A single‐nucleotide polymorphism prevented Gli binding and showed association with irritable bowel syndrome. We conclude that Gli1 and Gli2 repress ANO1 by a novel mechanism that is independent of Gli cleavage and that has a role in gastrointestinal function.—Mazzone, A., Gibbons, S. J., Eisenman, S. T., Strege, P. R., Zheng, T., D'Amato, M., Ordog, T., Fernandez‐Zapico, M. E., Farrugia, G. Direct repression of anoctamin 1 (ANO1) gene transcription by Gli proteins. FASEB J. 33, 6632–6642 (2019). www.fasebj.org

AbstractObjectiveWe identified a pedigree over five generations with 49 members, some of whom had chronic megacolon presenting in adolescence or adulthood. We aimed to assess the genetic cause of chronic megacolon through clinical and DNA studies.DesignAfter ethical approval and informed consent, family members provided answers to standard bowel disease questionnaires, radiological or surgical records, and DNA (buccal mucosal scraping). Exome DNA sequencing of colon tissue or blood DNA from seven family members with colon or duodenal dilatation, or no megacolon (n = 1) was carried out. Sanger sequencing was performed in 22 additional family members to further evaluate candidate variants. The study focused on genes of potential relevance to enteric nerve (ENS) maturation and Hirschsprung's disease or megacolon, based on the literature (GFRA1, NKX2‐1, KIF26A, TPM3, ACTG2, SCN10A, and C17orf107 [CHRNE]) and other genetic variants that co‐segregated with megacolon in the six affected family members.ResultsInformation was available in all except five members alive at time of study; among 30 members who provided DNA, six had definite megacolon, one megaduodenum, seven significant constipation without bowel dilatation, and 16 normal bowel function by questionnaire. Among genes studied, SEMA3F (g.3:50225360A>G; c1873A>G) was found in 6/6 family members with megacolon. The SEMA3F gene variant was assessed as potentially pathogenic, based on M‐CAP in silico prediction. SEMA3F function is associated with genes (KIT and PDGFRB) that impact intestinal pacemaker function.ConclusionFamilial chronic megacolon appears to be associated with SEMA3F, which is associated with genes impacting enteric nerve or pacemaker function.

AbstractBackgroundRAD21 is a double‐strand‐break repair protein and component of the cohesin complex with key roles in cellular functions. A RAD21 loss‐of‐function mutation was found in cases of chronic intestinal pseudo‐obstruction (CIPO) with associated enteric neuronal loss. Analysis of RAD21 expression in the enteric nervous system is lacking, thus we aimed to characterize RAD21 immunoreactivity (IR) in myenteric ganglia.MethodsDouble labeling immunofluorescence in mouse and human jejunum was used to determine colocalization of RAD21 with HuC/D, PGP9.5, neuronal nitric oxide synthase (nNOS), neuropeptide Y (NPY), choline acetyl transferase (ChAT), Kit, platelet‐derived growth factor receptor‐α (PDGFRα), and glial fibrillary acid protein (GFAP) IRs.ResultsA subset of PGP9.5‐ and HuC/D‐IR neuronal cell bodies and nerve fibers in the myenteric plexus of human and mouse small intestine also displayed cytoplasmic RAD21‐IR Cytoplasmic RAD21‐IR was found in 43% of HuC/D‐IR neurons in adult and neonatal mice but did not colocalize with nNOS. A subset of ChAT‐positive neurons had cytoplasmic RAD21‐IR Punctate RAD21‐IR was restricted to the nucleus in most cell types consistent with labeling of the cohesin complex. Cytoplasmic RAD21‐IR was not detected in interstitial cells of Cajal, fibroblast‐like cells or glia. Subsets of neurons in primary culture exhibited cytoplasmic RAD21‐IR Suppression of RAD21 expression by shRNA knockdown abolished RAD21‐IR in cultured neurons.ConclusionsOur data showing cytoplasmic RAD21 expression in enteric neurons provide a basis toward understanding how mutations of this gene may contribute to altered neuronal function/survival thus leading to gut‐motor abnormalities.

Abstract Background Gastric emptying is a complex physiological process regulating the division of a meal into smaller partitions for the small intestine. Disrupted gastric emptying contributes to digestive disease, yet current measures may not reflect different mechanisms by which the process can be altered. Methods We have developed high temporal resolution solid and liquid gastric emptying breath tests in mice using [ 13 C]‐octanoic acid and off axis‐ integrated cavity output spectroscopy ( OA ‐ ICOS ). Stretched gamma variate and 2‐component stretched gamma variate models fit measured breath excretion data. Key Results These assays detect acceleration and delay using pharmacological (7.5 mg/kg atropine) or physiological (nutrients, cold exposure stress, diabetes) manipulations and remain stable over time. High temporal resolution resolved complex excretion curves with 2 components, which was more prevalent in mice with delayed gastric emptying following streptozotocin‐induced diabetes. There were differences in the gastric emptying of Balb/c vs C57Bl6 mice, with slower gastric emptying and a greater occurrence of two‐phase gastric emptying curves in the latter strain. Gastric emptying of C57Bl6 could be accelerated by halving the meal size, but with no effect on the occurrence of two‐phase gastric emptying curves. A greater proportion of two‐phase gastric emptying was induced in Balb/c mice with the administration of PYY (8‐80 nmol) 60 min following meal ingestion. Conclusions and Inferences Collectively, these results demonstrate the utility of high temporal resolution gastric emptying assays. Two‐phase gastric emptying is more prevalent than previously reported, likely involves intestinal feedback, but contributes little to the overall rate of gastric emptying.

Objective Blunted tachycardia during hypotension is a characteristic feature of patients with autonomic failure, but the range has not been defined. This study reports the range of orthostatic heart rate (HR) changes in patients with autonomic failure caused by neurodegenerative synucleinopathies. Methods Patients evaluated at sites of the U.S. Autonomic Consortium (NCT01799915) underwent standardized autonomic function tests and full neurological evaluation. Results We identified 402 patients with orthostatic hypotension (OH) who had normal sinus rhythm. Of these, 378 had impaired sympathetic activation (ie, neurogenic OH) and based on their neurological examination were diagnosed with Parkinson disease, dementia with Lewy bodies, pure autonomic failure, or multiple system atrophy. The remaining 24 patients had preserved sympathetic activation and their OH was classified as nonneurogenic, due to volume depletion, anemia, or polypharmacy. Patients with neurogenic OH had twice the fall in systolic blood pressure (SBP; −44 ± 25 vs −21 ± 14 mmHg [mean ± standard deviation], p < 0.0001) but only one‐third of the increase in HR of those with nonneurogenic OH (8 ± 8 vs 25 ± 11 beats per minute [bpm], p < 0.0001). A ΔHR/ΔSBP ratio of 0.492 bpm/mmHg had excellent sensitivity (91.3%) and specificity (88.4%) to distinguish between patients with neurogenic from nonneurogenic OH (area under the curve = 0.96, p < 0.0001). Within patients with neurogenic OH, HR increased more in those with multiple system atrophy ( p = 0.0003), but there was considerable overlap with patients with Lewy body disorders. Interpretation A blunted HR increase during hypotension suggests a neurogenic cause. A ΔHR/ΔSBP ratio < 0.5 bpm/mmHg is diagnostic of neurogenic OH. Ann Neurol 2018;83:522–531

The SCN5A-encoded voltage-gated mechanosensitive Na+channel NaV1.5 is expressed in human gastrointestinal smooth muscle cells and interstitial cells of Cajal. NaV1.5 contributes to smooth muscle electrical slow waves and mechanical sensitivity. In predominantly Caucasian irritable bowel syndrome (IBS) patient cohorts, 2–3% of patients have SCN5A missense mutations that alter NaV1.5 function and may contribute to IBS pathophysiology. In this study we examined a racially and ethnically diverse cohort of IBS patients for SCN5A missense mutations, compared them with IBS-negative controls, and determined the resulting NaV1.5 voltage-dependent and mechanosensitive properties. All SCN5A exons were sequenced from somatic DNA of 252 Rome III IBS patients with diverse ethnic and racial backgrounds. Missense mutations were introduced into wild-type SCN5A by site-directed mutagenesis and cotransfected with green fluorescent protein into HEK-293 cells. NaV1.5 voltage-dependent and mechanosensitive functions were studied by whole cell electrophysiology with and without shear force. Five of 252 (2.0%) IBS patients had six rare SCN5A mutations that were absent in 377 IBS-negative controls. Six of six (100%) IBS-associated NaV1.5 mutations had voltage-dependent gating abnormalities [current density reduction (R225W, R433C, R986Q, and F1293S) and altered voltage dependence (R225W, R433C, R986Q, G1037V, and F1293S)], and at least one kinetic parameter was altered in all mutations. Four of six (67%) IBS-associated SCN5A mutations (R225W, R433C, R986Q, and F1293S) resulted in altered NaV1.5 mechanosensitivity. In this racially and ethnically diverse cohort of IBS patients, we show that 2% of IBS patients harbor SCN5A mutations that are absent in IBS-negative controls and result in NaV1.5 channels with abnormal voltage-dependent and mechanosensitive function.NEW & NOTEWORTHY The voltage-gated Na+channel NaV1.5 contributes to smooth muscle physiology and electrical slow waves. In a racially and ethnically mixed irritable bowel syndrome cohort, 2% had mutations in the NaV1.5 gene SCN5A. These mutations were absent in irritable bowel syndrome-negative controls. Most mutant NaV1.5 channels were loss of function in voltage dependence or mechanosensitivity.