Chronic diarrhoea due to trichohepatoenteric syndrome (THES) in an infant.

An infant was admitted with suspected postinfectious malabsorption with watery diarrhoea, fever and failure to thrive. She had dehydration, acute kidney injury and metabolic acidosis, which were corrected with intravenous fluids and managed with empiric antibiotics and prophylactic antifungals. She also developed Escherichia coli sepsis, meningitis and Candida skin infections during hospitalisation, which were treated according to the culture reports. Intrauterine growth restriction, woolly hair and a broad nasal bridge with chronic refractory diarrhoea prompted genetic testing to rule out syndromic diarrhoea. Whole-exome sequencing revealed a pathogenic compound heterozygous mutation causing trichohepatoenteric syndrome. She succumbed to severe infections at 80 days of life. The condition is rare, and no established guidelines or specific treatments exist; the focus is to promote optimal growth through parenteral nutrition, elemental formula and infection control. Early suspicion and molecular genetic testing can help reduce the time to diagnosis, treatment and genetic counselling.

Long term outcomes in children with trichohepatoenteric syndrome.

Trichohepatoenteric syndrome (THES) is a rare autosomal recessive disorder caused by mutations in either TTC37 or SKIV2L, usually leading to congenital diarrhea as part of a multisystem disease. Here, we report on the natural history of the disease for the largest UK cohort of patients with THES from 1996 to 2020. We systematically reviewed the clinical records and pathological specimens of patients diagnosed with THES managed in a single tertiary pediatric gastroenterology unit. Between 1996 and 2020, 13 patients (7 female and 6 male) were diagnosed with THES either by mutation analysis or by clinical phenotype. Two patients died from complications of infection. All patients received parenteral nutrition (PN) of which six patients were weaned off PN. All patients had gastrointestinal tract inflammation on endoscopy. Almost half of the cohort were diagnosed with monogenic inflammatory bowel disease (IBD) by the age of 11 years, confirmed by endoscopic and histological findings. Protracted diarrhea causing intestinal failure improves with time in all patients with THES, but monogenic IBD develops in later childhood that is refractory to conventional IBD treatments. Respiratory issues contribute to significant morbidity and mortality, and good respiratory care is crucial to prevent comorbidity.

The mammalian SKIV2L RNA exosome is essential for early B cell development.

The SKIV2L RNA exosome is an evolutionarily conserved RNA degradation complex in the eukaryotes. Mutations in the SKIV2L gene are associated with a severe inherited disorder, trichohepatoenteric syndrome (THES), with multisystem involvement but unknown disease mechanism. Here, we reported a THES patient with SKIV2L mutations showing severe primary B cell immunodeficiency, hypogammaglobulinemia, and kappa-restricted plasma cell dyscrasia but normal T cell and NK cell function. To corroborate these findings, we made B cell-specific Skiv2l knockout mice (Skiv2lfl/flCd79a-Cre), which lacked both conventional B-2 and innate-like B-1 B cells in the periphery and secondary lymphoid organs. This was linked to a requirement of SKIV2L RNA exosome activity in the bone marrow during early B cell development at the pro-B cell to large pre-B cell transition. Mechanistically, Skiv2l-deficient pro-B cells exhibited cell cycle arrest and DNA damage. Furthermore, loss of Skiv2l led to substantial out-of-frame V(D)J rearrangement of immunoglobulin heavy chain and severely reduced surface expression of µH, both of which are crucial for pre-BCR signaling and proliferative burst during early B cell development. Together, our data demonstrated a crucial role for SKIV2L RNA exosome in early B cell development in both human and mice by ensuring proper V(D)J recombination and Igh expression, which serves as the molecular basis for immunodeficiency associated with THES.

Tricho-Hepato-Eenteric Syndrome: Same Genotype but Different Phenotypes in Two Pakistani Children.

Tricho-hepato-enteric syndrome (THES) is characterised by infantile diarrhea with characteristic facies, trichorrhexis nodosa and hepatic involvement. The underlying genetic mutation is in tetratricopeptide repeat domain 37 (TTC37) gene. It is a very rare syndrome and only 44 cases have been reported so far in the medical literature. We recently diagnosed two children with THES on genetic analysis, who had same genotype but different phenotypes. Using these cases as a precedent, we reviewed what is known about this rare syndrome, as well as the novelties in our cases and treatment options. Key Words: Chronic diarrhea, Liver disease, Genetic mutation, TTC37.

Cytoplasmic RNA quality control failure engages mTORC1-mediated autoinflammatory disease.

Inborn errors of nucleic acid metabolism often cause aberrant activation of nucleic acid sensing pathways, leading to autoimmune or autoinflammatory diseases. The SKIV2L RNA exosome is cytoplasmic RNA degradation machinery that was thought to be essential for preventing the self-RNA-mediated interferon (IFN) response. Here, we demonstrate the physiological function of SKIV2L in mammals. We found that Skiv2l deficiency in mice disrupted epidermal and T cell homeostasis in a cell-intrinsic manner independently of IFN. Skiv2l-deficient mice developed skin inflammation and hair abnormality, which were also observed in a SKIV2L-deficient patient. Epidermis-specific deletion of Skiv2l caused hyperproliferation of keratinocytes and disrupted epidermal stratification, leading to impaired skin barrier with no appreciable IFN activation. Moreover, Skiv2l-deficient T cells were chronically hyperactivated and these T cells attacked lesional skin as well as hair follicles. Mechanistically, SKIV2L loss activated the mTORC1 pathway in both keratinocytes and T cells. Both systemic and topical rapamycin treatment of Skiv2l-deficient mice ameliorated epidermal hyperplasia and skin inflammation. Together, we demonstrate that mTORC1, a classical nutrient sensor, also senses cytoplasmic RNA quality control failure and drives autoinflammatory disease. We also propose SKIV2L-associated trichohepatoenteric syndrome (THES) as a new mTORopathy for which sirolimus may be a promising therapy.

Expanding the clinical spectrum in trichohepatoenteric syndrome.

Trichohepatoenteric syndrome (THES) is a very rare autosomal recessive genetic disorder, which is characterized by intractable diarrhea during infancy, dysmorphic features, immunodeficiency, and a failure to thrive. There are still significant difficulties for patients and clinicians in terms of the management of THES, even though its molecular basis has been uncovered in the last decade. In this article, we have presented two cases relating to siblings that have been diagnosed with the condition. Concerning one of the patients, we described a novel variation (c.2114 + 5G > A) in the TTC37 gene and a mild clinical course; meanwhile, the other one was clinically diagnosed with THES at 17 years of age, but they had seizures and died suddenly. These cases expand the spectrum of clinical findings in relation to THES.

Liver Pathology, Including MOC31 Immunohistochemistry, in Congenital Tufting Enteropathy.

Congenital tufting enteropathy (CTE) is a rare heritable cause of intractable diarrhea due to EPCAM mutation. Pathologic findings include intestinal villous atrophy, tufted discohesive tear-drop-shaped epithelium, and a normal brush border. In affected patients, absent intestinal epithelial cell adhesion molecule (EpCAM) expression results in loss of MOC31 immunostaining. CTE liver pathology has not yet been described. We identified CTE patients with liver biopsies and reviewed clinicopathologic material including MOC31 immunohistochemistry. Three CTE patients had 4 liver core biopsies (at ages 1, 5, 7, and 16 y), 2 for preintestinal transplant evaluation, and 2 (from a single patient) for pretreatment assessment of chronic hepatitis C; all had received parenteral nutrition (PN). All samples showed loss of biliary epithelial polarization and mild portal and lobular inflammation. Only the hepatitis C patient demonstrated fibrosis. One patient each had lobular neutrophilic microabscesses and macrovesicular steatosis. Proliferative ductular reactions were absent in CTE patients but present in all controls on PN for other reasons. MOC31 was absent in biliary epithelium and hepatocytes of all CTE patients; controls showed consistent strong membranous biliary epithelial and patchy membranous periportal hepatocyte staining. Our data show that, histologically, hepatopathy in CTE can be difficult to separate from comorbid disease including PN effect; however, the absent ductular reaction may be characteristic. MOC31 localization in the biliary epithelium and zone 1 hepatocytes of controls suggests these compartments of the liver might be most susceptible to effects of EpCAM deficiency. In addition, we validate the liver as suitable tissue for CTE diagnosis using MOC31 immunohistochemistry.

Outcome associated with EPCAM founder mutation c.499dup in Qatar.

Tufting enteropathy (TE) is a rare autosomal recessive congenital enteropathy that usually requires long-term parenteral nutrition (PN). In the Arabic Peninsula, four distinct EPCAM mutations have been identified to cause TE. As consanguineous marriages are socially favored, pre-marital and pre-conception testing has become a critical disease prevention strategy. This study aimed to identify the pathogenic EPCAM mutations causing TE in Qatari families and determine possible genotype-phenotype correlations. Twenty-two TE patients from seven multiplex families with TE were identified. Blood samples were collected from patients and first-degree relatives. Exons of the gene were amplified and sequenced. Retrospective chart review and/or family interviews were conducted to determine phenotypic characteristics of the disease. Sequence analysis revealed a single, previously described c.499dup mutation in exon 5 of all families tested, suggesting a founder effect. Of the 18 patients whose full clinical information was available, three patients (17%) were off PN with a good quality of life, without intestinal transplantation, and one (6%) was receiving partial PN. Our patients with TE were severely stunted compared to a similar group of patients receiving long-term PN for short bowel syndrome, suggesting that this could possibly be due to TE rather than secondary to inadequate nutrition. Our study identified the EPCAM mutation c.499dup as the genetic defect causing TE in all the participant Qatari families. This finding should facilitate early diagnosis of TE and genetic counseling. Furthermore, it should aid in the prevention of TE through pre-marital screening, antenatal diagnosis, and pre-implantation genetic diagnosis.

Amelioration of Congenital Tufting Enteropathy in EpCAM (TROP1)-Deficient Mice via Heterotopic Expression of TROP2 in Intestinal Epithelial Cells.

TROP1 (EpCAM) and TROP2 are homologous cell surface proteins that are widely expressed, and often co-expressed, in developing and adult epithelia. Various functions have been ascribed to EpCAM and TROP2, but responsible mechanisms are incompletely characterized and functional equivalence has not been examined. Adult intestinal epithelial cells (IEC) express high levels of EpCAM, while TROP2 is not expressed. EpCAM deficiency causes congenital tufting enteropathy (CTE) in humans and a corresponding lethal condition in mice. We expressed TROP2 and EpCAM in the IEC of EpCAM-deficient mice utilizing a villin promoter to assess EpCAM and TROP2 function. Expression of EpCAM or TROP2 in the IEC of EpCAM knockout mice prevented CTE. TROP2 rescue (T2R) mice were smaller than controls, while EpCAM rescue (EpR) mice were not. Abnormalities were observed in the diameters and histology of T2R small intestine, and Paneth and stem cell markers were decreased. T2R mice also exhibited enlarged mesenteric lymph nodes, enhanced permeability to 4 kDa FITC-dextran and increased sensitivity to detergent-induced colitis, consistent with compromised barrier function. Studies of IEC organoids and spheroids revealed that stem cell function was also compromised in T2R mice. We conclude that EpCAM and TROP2 exhibit functional redundancy, but they are not equivalent.

Congenital Tufting Enteropathy-Associated Mutant of Epithelial Cell Adhesion Molecule Activates the Unfolded Protein Response in a Murine Model of the Disease.

Congenital tufting enteropathy (CTE) is a rare chronic diarrheal disease of infancy caused by mutations in epithelial cell adhesion molecule (EpCAM). Previously, a murine CTE model showed mis-localization of EpCAM away from the basolateral cell surface in the intestine. Here we demonstrate that mutant EpCAM accumulated in the endoplasmic reticulum (ER) where it co-localized with ER chaperone, GRP78/BiP, revealing potential involvement of ER stress-induced unfolded protein response (UPR) pathway in CTE. To investigate the significance of ER-localized mutant EpCAM in CTE, activation of the three UPR signaling branches initiated by the ER transmembrane protein components IRE1, PERK, and ATF6 was tested. A significant reduction in BLOS1 and SCARA3 mRNA levels in EpCAM mutant intestinal cells demonstrated that regulated IRE1-dependent decay (RIDD) was activated. However, IRE1 dependent XBP1 mRNA splicing was not induced. Furthermore, an increase in nuclear-localized ATF6 in mutant intestinal tissues revealed activation of the ATF6-signaling arm. Finally, an increase in both the phosphorylated form of the translation initiation factor, eIF2α, and ATF4 expression in the mutant intestine provided support for activation of the PERK-mediated pathway. Our results are consistent with a significant role for UPR in gastrointestinal homeostasis and provide a working model for CTE pathophysiology.

Congenital Diarrheal Syndromes.

Congenital diarrheal disorders are heterogeneous conditions characterized by diarrhea with onset in the first years of life. They range from simple temporary conditions, such as cow's milk protein intolerance to irreversible complications, such as microvillous inclusion disease with significant morbidity and mortality. Advances in genomic medicine have improved our understanding of these disorders, leading to an ever-increasing list of identified causative genes. The diagnostic approach to these conditions consists of establishing the presence of diarrhea by detailed review of the history, followed by characterizing the composition of the diarrhea, the response to fasting, and with further specialized testing.

Matriptase drives early-onset intestinal failure in a mouse model of congenital tufting enteropathy.

Syndromic congenital tufting enteropathy (CTE) is a life-threatening recessive human genetic disorder that is caused by mutations in SPINT2, encoding the protease inhibitor HAI-2, and is characterized by severe intestinal dysfunction. We recently reported the generation of a Spint2-deficient mouse model of CTE. Here, we show that the CTE-associated early-onset intestinal failure and lethality of Spint2-deficient mice is caused by unchecked activity of the serine protease matriptase. Macroscopic and histological defects observed in the absence of HAI-2, including villous atrophy, luminal bleeding, loss of mucin-producing goblet cells, loss of defined crypt architecture and the resulting acute inflammatory response in the large intestine, were all prevented by intestinal-specific inactivation of the St14 gene encoding matriptase. The CTE-associated loss of the cell junctional proteins EpCAM and claudin 7 was also prevented. As a result, inactivation of intestinal matriptase allowed Spint2-deficient mice to gain weight after birth and dramatically increased their lifespan. These data implicate matriptase as a causative agent in the development of CTE and may provide a new target for the treatment of CTE in individuals carrying SPINT2 mutations.This article has an associated 'The people behind the papers' interview.

Enteroids expressing a disease-associated mutant of EpCAM are a model for congenital tufting enteropathy.

Congenital tufting enteropathy (CTE) is an autosomal recessive disease characterized by severe intestinal failure in infancy and mutations in the epithelial cell adhesion molecule (EPCAM) gene. Previous studies of CTE in mice expressing mutant EpCAM show neonatal lethality. Hence, to study the cellular, molecular, and physiological alterations that result from EpCAM mutation, a tamoxifen-inducible mutant EpCAM enteroid model has been generated. The presence of mutant EpCAM in the model was confirmed at both mRNA and protein levels. Immunofluorescence microscopy demonstrated the reduced expression of mutant EpCAM. Mutant enteroids had reduced budding potential as well as significantly decreased mRNA expression for epithelial lineage markers (Mucin 2, lysozyme, sucrase-isomaltase), proliferation marker Ki67, and secretory pathway transcription factors (Atoh1, Hnf1b). Significantly decreased numbers of Paneth and goblet cells were confirmed by staining. These findings were correlated with intestinal tissue from CTE patients and the mutant mice model that had significantly fewer Paneth and goblet cells than in healthy counterparts. FITC-dextran studies demonstrated significantly impaired barrier function in monolayers derived from mutant enteroids compared with control monolayers. In conclusion, we have established an ex vivo CTE model. The role of EpCAM in the budding potential, differentiation, and barrier function of enteroids is noted. Our study establishes new facets of EpCAM biology that will aid in understanding the pathophysiology of CTE and role of EpCAM in health and disease.NEW & NOTEWORTHY Here, we develop a novel ex vivo enteroid model for congenital tufting enteropathy (CTE) based on epithelial cell adhesion molecule (EPCAM) gene mutations found in patients. With this model we demonstrate the role of EpCAM in maintaining the functional homeostasis of the intestinal epithelium, including differentiation, proliferation, and barrier integrity. This study further establishes a new direction in EpCAM biology that will help in understanding the detailed pathophysiology of CTE and role of EpCAM.

Tricho-hepatic-enteric syndrome (THES) without intractable diarrhoea.

Tricho-hepatic-enteric syndrome (THES) is a genetically heterogeneous rare syndrome (OMIM: 222470 (THES1) and 614602 (THES2)) that typically presents in the neonatal period with intractable diarrhoea, intra-uterine growth retardation (IUGR), facial dysmorphism, and hair and skin changes. THES is associated with pathogenic variants in either TTC37 or SKIV2L; both are components of the human SKI complex, an RNA exosome cofactor. We report an 8 year old girl who was diagnosed with THES by the Undiagnosed Disease Program-WA with compound heterozygous pathogenic variants in SKIV2L. While THES was considered in the differential diagnosis, the absence of protracted diarrhoea delayed definitive diagnosis. We therefore suggest that SKIV2L testing should be considered in cases otherwise suggestive of THES, but without the characteristic diarrhoea. We expand the phenotypic spectrum while reviewing the current knowledge on SKIV2L.

Clinical and genetic spectrum of children with congenital diarrhea and enteropathy in China.

PURPOSE: Genetic sequencing for children with congenital diarrhea and enteropathy (CODE) has important implications for the diagnosis, prognosis, and implementation of precision medicine. METHODS: We performed exome sequencing or targeted panel sequencing on 137 children with CODE. Endoscopic, imaging, histological, and immunological assessments were also applied. Patients were divided into three subgroups: watery, fatty, and bloody diarrhea. RESULTS: The median age of onset among patients was 28.0 (interquartile range: 7.5-120.0) days. Genetic diagnosis was achieved in 88/137 (64.2%) of patients. The diagnostic rate was significantly higher in the neonatal group than in the group of patients who had disease onset within 2 years of age (p = 0.033). The diagnostic rates were 71.9% (46/64) for targeted gene panel sequencing and 57.5% (42/73) for exome sequencing (p = 0.081). We identified pathogenic variants in 17 genes. Based on genetic sequencing, 59.9% of patients were diagnosed with medically actionable disorders. Precision medicine was carried out by means of hematopoietic stem cell transplantation for patients with IL10RA, CYBB, or FOXP3 deficiency; pancreatic enzyme replacement for patients with SBDS or UBR1 deficiency; and a special diet for patients with SLC5A1 deficiency. The overall mortality rate was 14.6%. CONCLUSION: Single-gene disorders are common among CODE patients. Genetic diagnosis can improve therapy by enabling precision medicine.

EPCAM mutation update: Variants associated with congenital tufting enteropathy and Lynch syndrome.

The epithelial cell adhesion molecule gene (EPCAM, previously known as TACSTD1 or TROP1) encodes a membrane-bound protein that is localized to the basolateral membrane of epithelial cells and is overexpressed in some tumors. Biallelic mutations in EPCAM cause congenital tufting enteropathy (CTE), which is a rare chronic diarrheal disorder presenting in infancy. Monoallelic deletions of the 3' end of EPCAM that silence the downstream gene, MSH2, cause a form of Lynch syndrome, which is a cancer predisposition syndrome associated with loss of DNA mismatch repair. Here, we report 13 novel EPCAM mutations from 17 CTE patients from two separate centers, review EPCAM mutations associated with CTE and Lynch syndrome, and structurally model pathogenic missense mutations. Statistical analyses indicate that the c.499dupC (previously reported as c.498insC) frameshift mutation was associated with more severe treatment regimens and greater mortality in CTE, whereas the c.556-14A>G and c.491+1G>A splice site mutations were not correlated with treatments or outcomes significantly different than random simulation. These findings suggest that genotype-phenotype correlations may be useful in contributing to management decisions of CTE patients. Depending on the type and nature of EPCAM mutation, one of two unrelated diseases may occur, CTE or Lynch syndrome.

A novel TTC37 mutation causing clinical symptoms of trichohepatoenteric syndrome such as pyoderma gangrenosum and immunodeficiency without severe diarrhea

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Reversible deficits in apical transporter trafficking associated with deficiency in diacylglycerol acyltransferase.

Deficiency in diacylglycerol acyltransferase (DGAT1) is a rare cause of neonatal diarrhea, without a known mechanism or in vitro model. A patient presenting at our institution at 7 weeks of life with failure to thrive and diarrhea was found by whole-exome sequencing to have a homozygous DGAT1 truncation mutation. Duodenal biopsies showed loss of DGAT1 and deficits in apical membrane transporters and junctional proteins in enterocytes. When placed on a very low-fat diet, the patient's diarrhea resolved with normalization of brush border transporter localization in endoscopic biopsies. DGAT1 knockdown in Caco2-BBe cells modeled the deficits in apical trafficking, with loss of apical DPPIV and junctional occludin. Elevation in cellular lipid levels, including diacylglycerol (DAG) and phospholipid metabolites of DAG, was documented by lipid analysis in DGAT1 knockdown cells. Culture of the DGAT1 knockdown cells in lipid-depleted media led to re-establishment of occludin and return of apical DPPIV. DGAT1 loss appears to elicit global changes in enterocyte polarized trafficking that could account for deficits in absorption seen in the patient. The in vitro modeling of this disease should allow for investigation of possible therapeutic targets.

Tricho-Hepato-Enteric Syndrome mutation update: Mutations spectrum of TTC37 and SKIV2L, clinical analysis and future prospects.

Tricho-Hepato-Enteric syndrome (THES) is a very rare autosomal recessive syndromic enteropathy caused by mutations of either TTC37 or SKIV2L genes. Very little is known of these two gene products in mammals nor of the pathophysiology of the disease. Since the identification of the genes, we have set up the molecular diagnostic of THES in routine, gathering a large cohort with clinical and molecular data. Here, we report the phenotype and genotype analysis of this cohort together with an extensive literature review of THES cases worldwide, that is, 96 individuals harboring mutations in one gene or the other. We set up locus-specific databases for both genes and reviewed the type of mutation as well as their localization in the proteins. No hot spot is evidenced for any type of mutation. The phenotypic analysis was first made on the whole cohort but is limited due to heterogeneity in clinical descriptions. We then examined the lab diagnostic cohort in detail for clinical manifestations. For the first time, we are able to suggest that patients lacking SKIV2L seem more severely affected than those lacking TTC37, in terms of liver damage and prenatal growth impairment.