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

Bi-allelic variants in IPO8 cause a connective tissue disorder associated with cardiovascular defects, skeletal abnormalities, and immune dysregulation.

Dysregulated transforming growth factor TGF-β signaling underlies the pathogenesis of genetic disorders affecting the connective tissue such as Loeys-Dietz syndrome. Here, we report 12 individuals with bi-allelic loss-of-function variants in IPO8 who presented with a syndromic association characterized by cardio-vascular anomalies, joint hyperlaxity, and various degree of dysmorphic features and developmental delay as well as immune dysregulation; the individuals were from nine unrelated families. Importin 8 belongs to the karyopherin family of nuclear transport receptors and was previously shown to mediate TGF-β-dependent SMADs trafficking to the nucleus in vitro. The important in vivo role of IPO8 in pSMAD nuclear translocation was demonstrated by CRISPR/Cas9-mediated inactivation in zebrafish. Consistent with IPO8's role in BMP/TGF-β signaling, ipo8-/- zebrafish presented mild to severe dorso-ventral patterning defects during early embryonic development. Moreover, ipo8-/- zebrafish displayed severe cardiovascular and skeletal defects that mirrored the human phenotype. Our work thus provides evidence that IPO8 plays a critical and non-redundant role in TGF-β signaling during development and reinforces the existing link between TGF-β signaling and connective tissue defects

Diagnostic yield of next-generation sequencing in very early-onset inflammatory bowel diseases: a multicenter study (vol 12, pg 1104, 2021)

Transplantation and immunomodulatio

Increase of recurrent central line-associated bloodstream infections in children with home parenteral nutrition in a rehabilitation care facility compared to home

International audienceBACKGROUND AND AIMS: Central line-associated bloodstream infections (CLABSIs) are the main complication in children with home parenteral nutrition (HPN) and some patients develop recurrent CLABSIs (REC-CLABSIs), defined as two or more infections within six months. Our aims were to assess the incidence and to characterize the risk factors of REC-CLABSIs in children with HPN. METHODS: We characterized 79 HPN children from 2014 to 2019 and calculated the incidence of CLABSIs. To minimize the risk of bias related to the exposure time of the septic risk, we paired the patients according to their central venous catheter (CVC) dwell time. After analyzing the whole cohort, a univariate and multivariate unconditional logistic regression was performed on the paired cohort. RESULTS: We included 75 (94.9%) children with a mean age of 7.11 years. The rate of septicemia was 1.55/1000 CVC days, mainly with Staphyloccocus sp. The patients with recurrent CLABSIs (REC group) represented 25% of the cohort, with an incidence of 2.99/1000 CVC days. In the whole cohort, a higher risk of recurrent infections was significantly associated with a longer CVC dwell time (OR = 1.04, IC 95% [1.01-1.06], p = 0.004), and with care located in rehabilitation care facilities (RCF) compared to home (OR = 6, IC 95% [1.5-26.6], p = 0.012). When children were paired according to their CVC dwell time, only in univariate analysis did the care in RCF remain significant (OR = 6.27, IC 95% [1.21-32.5], p = 0.03). CONCLUSIONS: Recurrent CLABSIs incidence was 2.99/1000 CVC days. Our study suggests that preventive measures should be implemented especially in RCFs to reduce the proportion of children with recurrent infections. A multicenter study is needed to confirm our results in a larger cohort with several RCFs

A novel mutation of PCSK1 responsible for PC1/3 deficiency in two siblings

International audienceProprotein convertase 1 (PCSK1, PC1/3) deficiency is an uncommon cause of neonatal malabsorptive diarrhoea associated with endocrinopathies that are due to the disrupted processing of a large number of prohormones, including proinsulin. To date, only 26 cases have been reported. Herein, we describe two siblings with typical features including severe congenital diarrhoea, central diabetes insipidus, growth hormone deficiency, and hypoadrenalism. Next generation sequencing found a homozygous missense mutation in exon 5 of PCSK1 gene, c.500A\textgreaterC (p.Asp167Ala), located within the catalytic domain. Both patients presented a high level of proinsulin. In the first years of life they required parenteral nutrition and hormone replacement therapy. The patients, aged 3 and 1.5 years, experienced several infectious episodes associated with septic shocks. While the mechanism underlying intestinal failure remains poorly investigated, parenteral nutrition is essential in order to ensure normal growth in early childhood

Loss of UNC45A causes microvillus inclusion disease-like by impairing myosin-dependent epithelial morphogenesis

International audienc

Low Levels of Fecal Calprotectin 3 Months After Surgery Predict Subsequent Endoscopic Postoperative Remission in Crohn's Disease

International audienceBACKGROUND/AIMS: In Crohn's disease (CD) few data are available on the usefulness of monitoring fecal calprotectin (FC) in the early postoperative setting. We assessed prospectively the accuracy of FC measured 3 months after surgery to predict the risk of endoscopic postoperative recurrence (POR) within 1 year after resection. METHODS: In 55 consecutive CD patients who had undergone ileocolonic resection samples were collected 3 months after surgery for measuring serum CRP and FC. Endoscopic POR was assessed by ileocolonoscopy within 6-12 months (median 7 months). Receiver operating characteristic (ROC) curves were generated to assess accuracy of the markers, to determine the best threshold and to calculate sensitivity, specificity, positive and negative predictive values. RESULTS: In contrast with median CRP levels, median FC concentrations measured 3 months after surgery were significantly higher in patients who later experienced endoscopic POR (Rutgeerts ≥ i2) compared with those who stayed in endoscopic remission within the following 6-12 months (205 μg/g IQR [106-721] vs. 103 μg/g IQR [60-219], p = 0.008). Area under the ROC curve for FC was 0.71. The best cutoff value of FC to identify patients in subsequent endoscopic remission 3 months after surgery was 65 μg/g (96% sensitivity, 31% specificity, 50% positive and 91% negative predictive values). In multivariate analysis, FC \textless 65 µg/g at 3 months was the only factor associated with subsequent endoscopic remission. CONCLUSION: FC measured 3 months after surgery below 65 μg/g is an accurate marker to identify CD patients who will later stay in endoscopic remission within 1 year after resection

Clinical Heterogeneity of Immune Dysregulation, Polyendocrinopathy, Enteropathy, X-Linked Syndrome: A French Multicenter Retrospective Study

International audienceObjective: Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is an autoimmune disease caused by mutations in the forkhead box protein 3 gene (FOXP3), which encodes a key regulator of immune tolerance. The aim of this study was to describe the clinical heterogeneity of the disease in a national French cohort. Methods: Multicenter retrospective study of patients diagnosed with IPEX syndrome caused by mutations in FOXP3. Results: Thirty children from 26 families were included. Age at disease onset (median [first to third quartile]) was 1.5 mo [0-84] and at death 3.5 years [0-10.5] (n = 15) indicating a high heterogeneity. Initial presentation was diarrhoea (68%), type 1 diabetes (T1D; 25%), skin lesions (7%) and nephropathy (3%). During the course of the disease the following main symptoms were observed: diarrhoea (100%), skin lesions (85%), T1DM (50%), severe food allergies (39%), haematological disorders (28%), nephropathies (25%), hepatitis (14%) as well as the presence of a variety of autoantibodies. Immunosuppressive mono- or combination therapy led to improvement in eight children. Three boys displayed a stable disease course without any immunosuppressive medication. Overall 10-year survival rate was 43% (42% in transplanted patients and 52% in patients on immunosuppressive therapy). Five out of 22 identified FOXP3 mutations have not been described yet: c.-23 + 1G \textgreater A, c.-23 + 5G \textgreater A, c.264delC, c.1015C \textgreater T and c.1091A \textgreater G. The first two produced atypical, attenuated phenotypes. Missense and frameshift mutations affecting the forkhead domain were associated with poor survival (Gehan-Wilcoxon p = 0.002). Conclusion: The broad phenotypic heterogeneity of IPEX raises questions about modifying factors and justifies early FOXP3 sequencing in suspected cases