Mitchell D. Shub

Prevalence of endoscopic findings of erosive esophagitis in children: a population-based study.

Purpose: Symptoms of gastroesophageal reflux disease (GERD) occur in 2% to 7% of children. The manifestations of GERD can be limited to symptoms (eg, heartburn, regurgitation) or can be more complicated, such as erosive esophagitis, esophageal strictures, or Barrett esophagus. The prevalence of such GERD complications in children is unknown. The purpose of this study was to determine the prevalence of endoscopic findings of erosive esophagitis in children. Patients and Methods: All children ages 0 to 17 years, 11 months who underwent upper endoscopy that was recorded in the Pediatric Endoscopic Database System-Clinical Outcomes Research Initiative between 1999 and 2002 were included. Endoscopic reports that were incomplete or that did not include demographic features, indications for endoscopy, or endoscopic findings were excluded. Erosive esophagitis was defined either descriptively or by the Los Angeles classification. Esophageal biopsy was not evaluated. Results: A total of 7188 children who underwent upper endoscopy fulfilled the inclusion and exclusion criteria. Of those, 888 (12.4%) had erosive esophagitis. The median age of children with erosive esophagitis was 12.7 ± 4.9 years versus 10.0 ± 5.1 years in those without erosive esophagitis (P ≤ 0.0001). Of those with erosive esophagitis, 55.2% (490/888) were male, compared with 48.2% (3040/6300) in those without erosive esophagitis (P = 0.0001). Erosive esophagitis was found in 29 of 531 (5.5%) children ages 0 to 1 years and progressively increased to 106 in 542 individuals (19.6%) by age 17. Hiatal hernia was found in 68 (7.7%) of children with erosive esophagitis, compared with 157 (2.5%) without erosive esophagitis (P ≤ 0.0001. The prevalence of Barrett esophagus, esophageal stricture, ulcer, previous surgery, nodules, foreign body or retained food, and anatomic abnormalities was not significantly different between children with erosive esophagitis and those without. Conclusions: The frequency of erosive esophagitis is slightly higher in male children and increases with age. In contrast to erosive esophagitis in adults, there were no significant variations according to race or ethnicity. Hiatal hernia is the only endoscopic observation that predicts erosive esophagitis.

Myosin Vb uncoupling from RAB8A and RAB11A elicits microvillus inclusion disease

Microvillus inclusion disease (MVID) is a severe form of congenital diarrhea that arises from inactivating mutations in the gene encoding myosin Vb (MYO5B). We have examined the association of mutations in MYO5B and disruption of microvillar assembly and polarity in enterocytes. Stable MYO5B knockdown (MYO5B-KD) in CaCo2-BBE cells elicited loss of microvilli, alterations in junctional claudins, and disruption of apical and basolateral trafficking; however, no microvillus inclusions were observed in MYO5B-KD cells. Expression of WT MYO5B in MYO5B-KD cells restored microvilli; however, expression of MYO5B-P660L, a MVID-associated mutation found within Navajo populations, did not rescue the MYO5B-KD phenotype but induced formation of microvillus inclusions. Microvilli establishment required interaction between RAB8A and MYO5B, while loss of the interaction between RAB11A and MYO5B induced microvillus inclusions. Using surface biotinylation and dual immunofluorescence staining in MYO5B-KD cells expressing mutant forms of MYO5B, we observed that early microvillus inclusions were positive for the sorting marker SNX18 and derived from apical membrane internalization. In patients with MVID, MYO5B-P660L results in global changes in polarity at the villus tips that could account for deficits in apical absorption, loss of microvilli, aberrant junctions, and losses in transcellular ion transport pathways, likely leading to the MVID clinical phenotype of neonatal secretory diarrhea.

Rab11a regulates syntaxin 3 localization and microvillus assembly in enterocytes.

Rab11a is a key component of the apical recycling endosome that aids in the trafficking of proteins to the luminal surface in polarized epithelial cells. Utilizing conditional Rab11a‐knockout specific to intestinal epithelial cells, and human colonic epithelial CaCo2‐BBE cells with stable Rab11a knockdown, we examined the molecular and pathological impact of Rab11a deficiency on the establishment of apical cell polarity and microvillus morphogenesis. We demonstrate that loss of Rab11a induced alterations in enterocyte polarity, shortened microvillar length and affected the formation of microvilli along the lateral membranes. Rab11a deficiency in enterocytes altered the apical localization of syntaxin 3. These data affirm the role of Rab11a in apical membrane trafficking and the maintenance of apical microvilli in enterocytes.

Gastrospirillum hominis gastritis in a child with Celiac sprue

Gastrospirillum hominis is the original name applied to a non-Helicobacter pylori bacterium found in the human stomach (1). Like Helicobacter pylori, case reports have associated Gastrospirillum hominis with chronic active gastritis in adults (1± 11) and children (1, 5, 12± 14). To date, however, its pathologic significance remains unknown. We present a case of a 2-year-old girl with bloating, nausea with vomiting, anorexia, and diarrhea found to have G. hominisrelated gastritis as well as celiac disease on endoscopic biopsies.

Multiple duodenal ulcers: an unexpected finding in celiac disease.

Submissions for the Image of the Month should include high-quality TIF endoscopic images of unusual or informative findings. In addition, 1 or 2 other associated photographs, such as radiological or pathological images, can be submitted. A brief description of no more than 200 words should accompany the images. by members of the NASPGHAN Endoscopy and Procedures Committee, as well as Submissions are to be made online at www.jpgn.org, and will undergo peer review by the Journal.

Loss of MYO5B Leads to Reductions in Na+ Absorption with Maintenance of CFTR-dependent Cl- Secretion in Enterocytes

BACKGROUND & AIMSnInactivating mutations in MYO5B cause microvillus inclusion disease (MVID), but the physiological cause of the diarrhea associated with this disease is unclear. We investigated whether loss of MYO5B results inxa0aberrant expression of apical enterocyte transporters.nnnMETHODSnWe studied alterations in apical membrane transporters in MYO5B-knockout mice, as well as mice with tamoxifen-inducible, intestine-specific disruption of Myo5b (VilCreERT2;Myo5bflox/flox mice) or those not given tamoxifen (controls). Intestinal tissues were collected from mice and analyzed by immunostaining, immunoelectron microscopy, or cultured enteroids were derived. Functions of brush border transporters in intestinal mucosa were measured in Ussing chambers. We obtained duodenal biopsy specimens from individuals with MVID and individuals without MVID (controls) and compared transporter distribution by immunocytochemistry.nnnRESULTSnCompared to intestinal tissues from littermate controls, intestinal tissues from MYO5B-knockout mice had decreased apical localization of SLC9A3 (also called NHE3), SLC5A1 (also called SGLT1), aquaporin (AQP) 7, and sucrase isomaltase, and subapical localization of intestinal alkaline phosphatase and CDC42. However, CFTR was present on apical membranes ofxa0enterocytes from MYO5B knockout and control mice. Intestinal biopsies from patients with MVID had subapical localization of NHE3, SGLT1, and AQP7, but maintained apical CFTR. After tamoxifen administration, VilCreERT2;Myo5bflox/flox mice lost apical NHE3, SGLT1, DRA, and AQP7, similar to germline MYO5B knockout mice. Intestinal tissues from VilCreERT2;Myo5bflox/flox mice had increased CFTR in crypts andxa0CFTR localized to the apical membranes of enterocytes. Intestinal mucosa from VilCreERT2;Myo5bflox/flox mice given tamoxifen did not have an intestinal barrier defect, based on Ussing chamber analysis, but did have decreased SGLT1 activity and increased CFTR activity.nnnCONCLUSIONSnAlthough trafficking of many apical transporters is regulated by MYO5B, trafficking of CFTR is largely independent of MYO5B. Decreased apical localization of NHE3, SGLT1, DRA, and AQP7 might be responsible for dysfunctional water absorption in enterocytes of patients with MVID. Maintenance of apical CFTR might exacerbate water loss by active secretion of chloride into the intestinal lumen.

Apical Membrane Alterations in Non-intestinal Organs in Microvillus Inclusion Disease

ObjectivesMicrovillus inclusion disease (MVID) is a severe form of neonatal diarrhea, caused mainly by mutations in MYO5B. Inactivating mutations in MYO5B causes depolarization of enterocytes in the small intestine, which gives rise to chronic, unremitting secretory diarrhea. While the pathology of the small intestine in MVID patients is well described, little is known about extraintestinal effects of MYO5B mutation.MethodsWe examined stomach, liver, pancreas, colon, and kidney in Navajo MVID patients, who share a single homozygous MYO5B-P660L (1979C>T p.Pro660Leu, exon 16). Sections were stained for markers of the apical membrane to assess polarized trafficking.ResultsNavajo MVID patients showed notable changes in H/K-ATPase-containing tubulovesicle structure in the stomach parietal cells. Colonic mucosa was morphologically normal, but did show losses in apical ezrin and Syntaxin 3. Hepatocytes in the MVID patients displayed aberrant canalicular expression of the essential transporters MRP2 and BSEP. The pancreas showed small fragmented islets and a decrease in apical ezrin in pancreatic ducts. Kidney showed normal primary cilia.ConclusionsThese findings indicate that the effects of the P660L mutation in MYO5B in Navajo MVID patients are not limited to the small intestine, but that certain tissues may be able to compensate functionally for alterations in apical trafficking.

176 Loss of Functional MYO5B in CaCo2-BBe Cells and Navajo MVID Patient Enterocytes Leads to Loss of Polarity and Deficits in Maintenance of Microvilli

Myosin Vb (MYO5B) is an actin based motor that localizes specific Rab small GTPases (Rab8a, Rab10, Rab11, and Rab25) to sub-apical domains in polarized epithelial cells. Microvillus Inclusion Disease (MVID) represents a pathophysiologic window into the apical trafficking process, because it arises as a result of inactivating mutations in MYO5B that leads to the loss of microvilli in intestinal enterocytes and chronic unremitting diarrhea in the affected newborns. Understanding how mutations in MYO5B lead to aberrant enterocyte phenotype will provide novel insights into the fundamental mechanisms governing apical recycling system trafficking, microvilli formation, and MVID. We hypothesize that MYO5B plays a crucial role in apical trafficking and polarization in enterocytes, and that defective MYO5B in MVID patients mislocalizes Rab small GTPases leading to disruption in apical transport and loss of polarity in enterocytes. To test this hypothesis we have established cellular models of aberrant enterocyte apical trafficking by stably knocking down MYO5B in CaCo2-BBE cells. The cells grown on permeable filters for 15 days were analyzed using immunostaining, Scanning EM, and Transmission EM to examine markers of apical and basolateral polarity, intracellular trafficking, and the establishment of apical microvilli. MYO5B KD knockdown (KD) caused a loss of microvilli and dispersal of Rab8a and Rab11acontaining vesicles from their usual subapical distribution to diffusely cytoplasmic in the cells. MYO5B KD elicited an increase in claudin-2 and a decrease in claudin-1 expression as well as a decrease in lateral membrane staining for p120-catenin (p120). MYO5B KD also caused a loss of apical active GTP-bound cdc42 in the cells. Rescue of theMYO5B KDwith synthetic MYO5B wild type elicited recovery of normal microvilli. However, re-expression of MYO5B(P660L), the Navajo MVID mutation, failed to rescue and in addition caused the formation of microvillus inclusions. Navajo MVID MYO5B(P660L) patient samples demonstrated a loss of p120 and a pseudostratified columnar epithelium at the villus tips where ezrin-staining microvillus inclusions were most predominant. Patient biopsies also showed aberrant localization of MYO5B, Rab8a, Rab11a, Rab11-FIP2, DPPIV, and Ezrin. Rab11a and MYO5B localized around microvillus inclusions, while Rab8a staining was diffuse. Importantly, while a severe loss of brush border was observed in cells at the tips of microvilli, the cells in the mid-villus appeared to have a preserved normal brush border. Our results suggest that MYO5B regulates the polarity of intestinal epithelial cells, thereby maintaining the functional brush border. The normal brush border seen in the proximal villi in the Navajo MVID patients suggests that the pathogenesis of MVID lies in a loss of polarity in enterocytes at the tips of intestinal villi.