Not all enteropathies are coeliac disease! Report of an infant with microvillus inclusion disease

Primary enteropathies of infancy comprise of epithelial defects including microvillus inclusion disease, tufting enteropathy, and enteroendocrine cell dysgenesis and autoimmune enteropathies. The diseases in this group cause severe chronic (>2-3 weeks) diarrhoea starting in the first weeks of life and resulting in failure to thrive in the infant. Duodenal biopsies show moderate villous shortening together with crypt hyperplasia which are the main features causing resemblance to coeliac disease. We, hereby, report a term-born male infant of consanguineous parents. His two siblings died during infancy. He developed watery, urine-like diarrhea on the 3rd day of his life. On the postnatal 6th day he weighed 2750 grams, became dehydrated and had metabolic acidosis. Upper GI endoscopy performed on the postnatal 20th day appeared normal. Light microscopic examination of the duodenal biopsy showed moderate villous blunting, with mildly increased inflammatory cells in the lamina propria or and intraepithelial lymphocytosis. Enterocytes at the villous tips showed an irregular vacuolated appearance in the apical cytoplasm with patchy absence of the brush border demonstared by PAS and CD10. Electron microscopy revealed intracytoplasmic inclusions that were lined by intact microvilli in the apical cytoplasm of enterocytes. As he was dependent on TPN and aggressive intravenous fluid replacement he was hospitalized throughout his life. He died when he was 3 years and 4 months old. Paediatric coeliac disease is in the differential diagnosis of primary enteropathies of childhood. The differentiation lies on duodenal biopsy interpretation together with genetic analysis to detect the underlying genetic defect in childhood enteropathies.

Altered MYO5B Function Underlies Microvillus Inclusion Disease: Opportunities for Intervention at a Cellular Level

Microvillus inclusion disease (MVID) is a congenital diarrheal disorder resulting in life-threatening secretory diarrhea in newborns. Inactivating and nonsense mutations in myosin Vb (MYO5B) have been identified in MVID patients. Work using patient tissues, cell lines, mice, and pigs has led to critical insights into the pathology of MVID and a better understanding of both apical trafficking in intestinal enterocytes and intestinal stem cell differentiation. These studies have demonstrated that loss of MYO5B or inactivating mutations lead to loss of apical sodium and water transporters, without loss of apical CFTR, accounting for the major pathology of the disease. In addition, loss of MYO5B expression induces the formation of microvillus inclusions through apical bulk endocytosis that utilizes dynamin and PACSIN2 and recruits tight junction proteins to the sites of bulk endosome formation. Importantly, formation of microvillus inclusions is not required for the induction of diarrhea. Recent investigations have demonstrated that administration of lysophosphatidic acid (LPA) can partially reestablish apical ion transporters in enterocytes of MYO5B KO mice. In addition, further studies have shown that MYO5B loss induces an imbalance in Wnt/Notch signaling pathways that can lead to alterations in enterocyte maturation and tuft cell lineage differentiation. Inhibition of Notch signaling leads to improvements in those cell differentiation deficits. These studies demonstrate that directed strategies through LPA receptor activation and Notch inhibition can bypass the inhibitory effects of MYO5B loss. Thus, effective strategies may be successful in MVID patients and other congenital diarrhea syndromes to reestablish proper apical membrane absorption of sodium and water in enterocytes and ameliorate life-threatening congenital diarrhea.

Monogenic mutations in four cases of neonatal-onset watery diarrhea and a mutation review in East Asia

BACKGROUND

Infants with neonatal-onset diarrhea present with intractable diarrhea in the first few weeks of life. A monogenic mutation is one of the disease etiologies and the use of next-generation sequencing (NGS) has made it possible to screen patients for their mutations.

MAIN BODY

We retrospectively reviewed the clinical data of four children from unrelated families, who presented with neonatal-onset, chronic, watery, non-bloody diarrhea. After genetic whole-exome sequencing, novel mutations were identified in the EPCAM gene of two children. Congenital chloride diarrhea was diagnosed in one case, which was associated with an SLC26A3 mutation, in which the patient presented with watery diarrhea, malnutrition, and hypochloremic alkalosis. Patient 4 was diagnosed with microvillus inclusion disease and possessed novel compound heterozygous mutations in the MYO5B gene. A review of the genetic variants of SLC26A3 reported in East Asia revealed that c.269_270 dupAA (p.G91Kfs*3) is the most frequent SLC26A3 mutation in China, compared with c.2063-1 G > T in Japan and Korea. EPCAM and MYO5B genetic variants were only sporadically reported in East Asia.

CONCLUSION

This study expands our knowledge of the clinical manifestations and molecular genetics of neonatal-onset watery diarrhea. Early diagnosis could be achieved by genomic analysis in those infants whose histology features are not typical. The discovery of four novel mutations in the EPCAM gene and two novel mutations in the MYO5B gene provides further etiological evidence for the association of genetic mutations with neonatal-onset diarrhea. To date, c.269_270 dupAA is the most frequent SLC26A3 mutation in China.

Congenital diarrhea in a newborn infant: A case report

BACKGROUND

Microvillus inclusion disease (MVID) is a rare autosomal recessive cause of severe congenital diarrhea with significant morbidity and mortality. Definitive treatment involves bowel transplant. The diagnosis of this condition can be challenging and a few genetic panels are available for the identification of the most common mutations. We present the case of an infant with MVID due to a mutation not reported in the literature before.

CASE SUMMARY

We report the case of an infant transferred to our institution with severe diarrhea of unknown etiology, failure to thrive, and significant metabolic derangements. An extensive work-up including stool studies for common gastrointestinal pathogens, abdominal ultrasound, esophagogastroduodenoscopy with duodenal biopsy and flexible sigmoidoscopy failed to reveal a diagnosis. Multiple dietary and formula regimens were introduced but all resulted in voluminous diarrhea. She remained on total parenteral nutrition (TPN) for the duration of her hospital stay. Genetic testing was done and she was subsequently found to have a novel mutation in the MYO5B gene [homozygous mutation for MYO5B c.1462del, p. (Ile488Leufs*93)] giving us the diagnosis of MVID. She remains on TPN while awaiting bowel transplant at the time of the compilation of this case report.

CONCLUSION

We report a novel mutation involved in MVID and highlight the importance of considering this disease when faced with a newborn presenting with life threatening diarrhea. At the time of this publication, 232 allelic variations of this gene (MIM#606540) exist in National Center for Biotechnology Information's database. Our patient's mutation has not been reported in literature as a cause of MVID.

A V0-ATPase-dependent apical trafficking pathway maintains the polarity of the intestinal absorptive membrane

Intestine function relies on the strong polarity of intestinal epithelial cells and the array of microvilli forming a brush border at their luminal pole. Combining a genetic RNA interference (RNAi) screen with in vivo super-resolution imaging in the Caenorhabditis elegans intestine, we found that the V0 sector of the vacuolar ATPase (V0-ATPase) controls a late apical trafficking step, involving Ras-related protein 11 (RAB-11)⁺ endosomes and the N-ethylmaleimide-sensitive factor-attachment protein receptor (SNARE) synaptosome-associated protein 29 (SNAP-29), and is necessary to maintain the polarized localization of both apical polarity modules and brush border proteins. We show that the V0-ATPase pathway also genetically interacts with glycosphingolipids and clathrin in enterocyte polarity maintenance. Finally, we demonstrate that silencing of the V0-ATPase fully recapitulates the severe structural, polarity and trafficking defects observed in enterocytes from individuals with microvillus inclusion disease (MVID) and use this new in vivo MVID model to follow the dynamics of microvillus inclusions. Thus, we describe a new function for V0-ATPase in apical trafficking and epithelial polarity maintenance and the promising use of the C. elegans intestine as an in vivo model to better understand the molecular mechanisms of rare genetic enteropathies.

Microvillus inclusion disease, a diagnosis to consider when abnormal stools and neurological impairments run together due to a rare syntaxin 3 gene mutation

BACKGROUND

Microvillus Inclusion Disease (MVID) was first described in the literature in 1978 with presentation of severe watery diarrhea, failure to thrive, and metabolic acidosis. Mutations in the myosin Vb (MYO5B) gene have been identified as causative for MVID, but other clinical manifestations and associations with novel mutations are lacking.

METHODS

We report a full-term infant admitted to the neonatal intensive care unit (NICU) with abdominal distension and inability to sustain full enteral feeds. A retrospective chart review and review of the literature was performed.

RESULTS

An infant with abnormal, mucoid-like stringy stools was incidentally found to have severe metabolic acidosis on routine lab monitoring. Acidosis corrected with total parenteral nutrition (TPN), but the infant experienced recurrent episodes of acidosis with enteral feeds. He was also noted to have abnormal ocular movements, fluctuating tonicity, and staring spells. He underwent an extensive workup and the diagnosis of microvillus inclusion disease was made by findings on electron microscopy. The diagnosis was confirmed with whole exome sequencing, showing a rare homozygous mutation in the syntaxin 3 (STX3) gene. This is the fifth reported patient with microvillus inclusion disease with a mutation in this gene, and the first with abnormal neurologic findings.

CONCLUSION

It is important to consider MVID in the differential diagnosis of a neonate or infant with abnormal stools, metabolic acidosis, with and without neurologic symptoms for prompt referral and treatment.

Intestinal epithelial cell polarity defects in disease: lessons from microvillus inclusion disease

The intestinal epithelium is a highly organized tissue. The establishment of epithelial cell polarity, with distinct apical and basolateral plasma membrane domains, is pivotal for both barrier formation and for the uptake and vectorial transport of nutrients. The establishment of cell polarity requires a specialized subcellular machinery to transport and recycle proteins to their appropriate location. In order to understand and treat polarity-associated diseases, it is necessary to understand epithelial cell-specific trafficking mechanisms. In this Review, we focus on cell polarity in the adult mammalian intestine. We discuss how intestinal epithelial polarity is established and maintained, and how disturbances in the trafficking machinery can lead to a polarity-associated disorder, microvillus inclusion disease (MVID). Furthermore, we discuss the recent developments in studying MVID, including the creation of genetically manipulated cell lines, mouse models and intestinal organoids, and their uses in basic and applied research.

Summary: Microvillus inclusion disease serves as a useful model to enhance our understanding of the intestinal trafficking and polarity machinery in health and disease.

Congenital Fatal Diarrhea in Newborns

Microvillus inclusion disease is a rare autosomal recessive disorder of intestinal epithelium causing intractable secretary diarrhea in the first two months of life and about 140 cases have been reported worldwide till now. Here authors report 2 cases of Microvillus inclusion disease (MVID) diagnosed in neonates by electron microscopy study of small intestinal biopsy.

Microvillus Inclusion Disease Variant in an Infant with Intractable Diarrhea

Microvillus inclusion disease (MVID) is a rare autosomal recessive congenital enteropathy characterized by intractable secretory diarrhea. We report a case of MVID variant with a homozygous gene mutation in syntaxin 3 (STX3). The patient is a male Saudi infant who presented shortly after birth with severe vomiting, metabolic acidosis, and mild diarrhea. Electron microscopy study for small intestinal biopsy was consistent with MVID. MYO5B gene mutation was excluded; subsequently, whole exome sequencing (WES) was performed, which revealed homozygous gene mutation in STX3. Using WES in clinical environment can be a useful tool for diagnosing difficult and rare inherited congenital enteropathies.

Concise Review: The Potential Use of Intestinal Stem Cells to Treat Patients with Intestinal Failure

Intestinal failure is a rare life‐threatening condition that results in the inability to maintain normal growth and hydration status by enteral nutrition alone. Although parenteral nutrition and whole organ allogeneic transplantation have improved the survival of these patients, current therapies are associated with a high risk for morbidity and mortality. Development of methods to propagate adult human intestinal stem cells (ISCs) and pluripotent stem cells raises the possibility of using stem cell‐based therapy for patients with monogenic and polygenic forms of intestinal failure. Organoids have demonstrated the capacity to proliferate indefinitely and differentiate into the various cellular lineages of the gut. Genome‐editing techniques, including the overexpression of the corrected form of the defective gene, or the use of CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 to selectively correct the monogenic disease‐causing variant within the stem cell, make autologous ISC transplantation a feasible approach. However, numerous techniques still need to be further optimized, including more robust ex vivo ISC expansion, native ISC ablation, and engraftment protocols. Large‐animal models can to be used to develop such techniques and protocols and to establish the safety of autologous ISC transplantation because outcomes in such models can be extrapolated more readily to humans. Stem Cells Translational Medicine2017;6:666–676

The zebrafish goosepimples/myosin Vb mutant exhibits cellular attributes of human microvillus inclusion disease

Microvillus inclusion disease (MVID) is a life-threatening enteropathy characterised by malabsorption and incapacitating fluid loss due to chronic diarrhoea. Histological analysis has revealed that enterocytes in MVID patients exhibit reduction of microvilli, presence of microvillus inclusion bodies and intestinal villus atrophy, whereas genetic linkage analysis has identified mutations in myosin Vb gene as the main cause of MVID. In order to understand the cellular basis of MVID and the associated formation of inclusion bodies, an animal model that develops ex utero and is tractable genetically as well as by microscopy would be highly useful. Here we report that the intestine of the zebrafish goosepimples (gsp)/myosin Vb (myoVb) mutant shows severe reduction in intestinal folds - structures similar to mammalian villi. The loss of folds is further correlated with changes in the shape of enterocytes. In striking similarity with MVID patients, zebrafish gsp/myoVb mutant larvae exhibit microvillus atrophy, microvillus inclusions and accumulation of secretory material in enterocytes. We propose that the zebrafish gsp/myoVb mutant is a valuable model to study the pathophysiology of MVID. Furthermore, owing to the advantages of zebrafish in screening libraries of small molecules, the gsp mutant will be an ideal tool to identify compounds having therapeutic value against MVID.

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myosin Vb is expressed in the zebrafish intestine.

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goosepimples/myosin Vb function is essential for epithelial morphogenesis in the zebrafish intestine.

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The goosepimples mutant recapitulates pathognomonic features of microvillus inclusion disease.

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The function of myosin Vb in the intestine is conserved between fish and mammals.

Generation of intestinal surface: an absorbing tale

The vertebrate small intestine requires an enormous surface area to effectively absorb nutrients from food. Morphological adaptations required to establish this extensive surface include generation of an extremely long tube and convolution of the absorptive surface of the tube into villi and microvilli. In this Review, we discuss recent findings regarding the morphogenetic and molecular processes required for intestinal tube elongation and surface convolution, examine shared and unique aspects of these processes in different species, relate these processes to known human maladies that compromise absorptive function and highlight important questions for future research.

Towards understanding microvillus inclusion disease

Microvillus inclusion disease (MVID) is characterised by onset of intractable life-threatening watery diarrhoea during infancy. Transmission electron microscopy demonstrates shortening or absence of apical microvilli, pathognomonic microvillus inclusions in mature enterocytes and subapical accumulation of periodic acid-Schiff-positive granules or vesicles confirming diagnosis. Mutations in MYO5B have been found to cause MVID. In two patients with MVID, whole-exome sequencing of DNA revealed homozygous truncating mutations in STX3. Mutations in these genes disrupt trafficking between apical cargo vesicles and the apical plasma membrane. Thus, disturbed delivery of certain brush border membrane proteins is a common defect in MVID.

[Intestinal failure and transplantation in microvillous inclusion disease]

INTRODUCTION

Microvillous inclusion disease is a rare autosomal recessive condition, characterized by severe secretory diarrhea that produces a permanent intestinal failure and dependency on parenteral nutrition. It usually begins in the neonatal period, and the only treatment at present is intestinal transplantation.

PATIENTS AND METHODS

A retrospective review was conducted on 6 patients (three males and three females) diagnosed with microvillous inclusion disease between 1998 and 2013.

RESULTS

All debuted in the first month of life, with a median age of three days (range, 3-30 days), and had secretory diarrhea dependent on parenteral nutrition, with fasting fecal volume of 150-200ml/kg/day. Light microscopy of duodenal biopsy samples showed varying degrees of villous atrophy without cryptic hyperplasia, accumulation of PAS positive material in the cytoplasm of enterocytes brush border, and anti-CD10 immunostaining was suggestive of intracytoplasmic inclusions. Diagnostic confirmation was performed with electron microscopy. Two of them had a genetic study, and showed mutations in MYO5B gene. Three died and three are alive; two of them with an intestinal transplantation and the third waiting for a multivisceral transplantation.

Myosin Vb and Rab11a regulate phosphorylation of ezrin in enterocytes

Microvilli at the apical surface of enterocytes allow the efficient absorption of nutrients in the intestine. Ezrin activation by its phosphorylation at T567 is important for microvilli development, but how such ezrin phosphorylation is controlled is not well understood. We demonstrate that a subset of kinases that phosphorylate ezrin closely co-distributes with apical recycling endosome marker Rab11a in the subapical domain. Expression of dominant-negative Rab11a mutant or depletion of the Rab11a-binding motor protein myosin Vb prevents the subapical enrichment of Rab11a and these kinases and inhibits ezrin phosphorylation and microvilli development, without affecting the polarized distribution of ezrin itself. We observe a similar loss of the subapical enrichment of Rab11a and the kinases and reduced phosphorylation of ezrin in microvillus inclusion disease, which is associated with MYO5B mutations, intestinal microvilli atrophy and malabsorption. Thus, part of the machinery for ezrin activation depends on recycling endosomes controlled by myosin Vb and Rab11a which, we propose, might act as subapical signaling platforms that enterocytes use to regulate development of microvilli and maintain human intestinal function.