UNC45A deficiency causes microvillus inclusion disease–like phenotype by impairing myosin VB–dependent apical trafficking

International audienceVariants in the UNC45A cochaperone have been recently associated with a syndrome combining diarrhea, cholestasis, deafness, and bone fragility. Yet the mechanism underlying intestinal failure in UNC45A deficiency remains unclear. Here, biallelic variants in UNC45A were identified by next-generation sequencing in 6 patients with congenital diarrhea. Corroborating in silico prediction, variants either abolished UNC45A expression or altered protein conformation. Myosin VB was identified by mass spectrometry as client of the UNC45A chaperone and was found misfolded in UNC45A(KO) Caco-2 cells. In keeping with impaired myosin VB function, UNC45A(KO) Caco-2 cells showed abnormal epithelial morphogenesis that was restored by full-length UNC45A, but not by mutant alleles. Patients and UNC45A(KO) 3D organoids displayed altered luminal development and microvillus inclusions, while 2D cultures revealed Rab11 and apical transporter mislocalization as well as sparse and disorganized microvilli. All those features resembled the subcellular abnormalities observed in duodenal biopsies from patients with microvillus inclusion disease. Finally, microvillus inclusions and shortened microvilli were evidenced in enterocytes from unc45a-deficient zebrafish. Taken together, our results provide evidence that UNC45A plays an essential role in epithelial morphogenesis through its cochaperone function of myosin VB and that UNC45A loss causes a variant of microvillus inclusion disease

Variation of plasma citrulline as a predictive factor for weaning off long-term parenteral nutrition in children with neonatal short bowel syndrome

Background & aims: Long-term parenteral nutrition (PN) is the mainstay of the therapeutic strategy in intestinal failure (IF) due to neonatal short bowel syndrome (SBS). Our aim was to identify prognostic factors for PN weaning and to assess if measuring plasma citrulline concentrations over time could account for the intestinal adaptation in progress. Methods: This retrospective study included children with neonatal SBS with surgical measurement of the residual bowel length and repeated plasma citrulline assessments during a 4-year follow-up. The degree of IF was assessed by the PN dependency index (PN caloric intake/Resting energy expenditure). The analysis was carried out according to SBS anatomical groups: end-jejunostomy (type 1), jejuno-colic (type 2) and jejuno-ileal anastomosis (type 3). Results: Fifty-five patients (8 type 1, 27 type 2, 20 type 3) were included. None of the patients with SBS type 1, 11 (41%) with type 2 and 11 (55%) with type 3 were weaned off during the follow-up period. Plasma citrulline levels significantly increased with time in patients who were finally weaned off PN; conversely, the levels did not consistently increase in patients who were still on PN at the end of the study period. There was an inverse relationship between plasma citrulline levels and the PN dependency index. The increasing citrulline levels had a positive effect on the probability of weaning, 2.7 times higher for each point increase in citrulline. No significant effect of age and residual bowel length at baseline was found. Conclusion: The increased plasma citrulline level over time in addition to the SBS anatomical type is a reliable marker for subsequent PN weaning. The prediction of PN weaning assessed solely by the residual bowel length or a single measurement of citrulline is insufficient and should also take into account the anatomical type of SBS and repeated measurements of plasma citrulline levels

Endoscopy

BACKGROUND: Esophagogastroduodenoscopy (EGD) is the standard method for diagnosis of esophageal and gastric varices in children. In this prospective study we evaluated the use of PillCam esophageal capsule endoscopy (ECE) in pediatric patients. METHODS: Patients aged 7 to 18 years presenting with portal hypertension and/or cirrhosis underwent ECE (PillCam ESO 2, Given Imaging Ltd.) followed by EGD. RESULTS: 102 patients were screened, 81 (52 boys; mean age 13.96 +/- 0.25 years) were included and 21 were excluded (16 for "candy test" failure). Esophageal varices were identified by EGD in 62 patients (77 %) and by ECE in 57 patients (70 %) using the de Franchis classification (DFC). The sensitivity of ECE for esophageal varices was 92 % and the specificity was 100 % using DFC. Based upon 57/81 patients with small, medium, and large varices on both ECE and EGD, using DFC, the sensitivity, specificity, positive (PPV) and negative predictive value (NPV) were 55 %, 92 %, 89 %, and 63 %, respectively, giving a total overall accuracy of 72 %. To improve sensitivity and specificity in classification of esophageal varices, we propose using a modified score. This score detected esophageal varices with 100 % sensitivity, 93 % specificity, 94 % PPV, and 100 % NPV, giving a total overall accuracy of 97 %. All patients preferred ECE over EGD. No capsule retention was recorded. CONCLUSIONS: ECE is a well-tolerated and safe procedure in children. Using the modified score, the sensitivity of ECE is currently sufficient to detect esophageal varices and replace EGD in infants with suspicion of esophageal varices or when EGD is refused