Abstract:Myosin Vb (MYO5B) is a motor protein that facilitates protein trafficking and recycling in polarized cells by RAB11- and RAB8-dependent mechanisms. Biallelic MYO5B mutations are identified in the majority of patients with microvillus inclusion disease (MVID). MVID is an intractable diarrhea of infantile onset with characteristic histopathologic findings that requires life-long parenteral nutrition or intestinal transplantation. A large number of such patients eventually develop cholestatic liver disease. Bi-al… Show more
“…For EM we analyzed duodenal samples from 2 patients with functional dyspepsia (one of them shown in Figures S1a–c and S4c,f ) and liver samples from one patient with Friedreich’s ataxia (shown in respective text figures), from one patient with alpha-1 antitrypsin deficiency (not shown), and from a healthy donor liver. All three patients MYO5B mutations with were genetically described recently [ 44 ].…”
Section: Resultsmentioning
confidence: 99%
“…Patient #1 is 35-year-old Caucasian male with compound heterozygous MYO5B-mutations: c.242A>G (p.His81Arg) and c.4798C>T (Gln1600*) [ 44 ]. Parental consanguinity is not known.…”
Section: Resultsmentioning
confidence: 99%
“…Patient #2 is a 12-year-old Arab female, daughter of consanguineous parents, with homozygous MYO5B-mutations: c1669G>T (p.Val557Leu) [ 44 ]. Disease onset was reported at 11 months of age with diarrhea and cholestasis.…”
Section: Resultsmentioning
confidence: 99%
“…Thus, the emerging field on MYO5B associated PFIC (MYO5B-PFIC) has focused on liver function and morphology of PFIC6 patients. Concerning MVID, typical intestinal symptoms were not present in several MYO5B-PFIC patients [ 39 , 42 , 44 ]. A detailed subcellular and ultrastructural characterization of the intestine in MYO5B-PFIC patients is lacking as yet.…”
Section: Introductionmentioning
confidence: 99%
“…The specific added value for ultrastructural pathology and more generally for disease-relevant immuno-histochemistry at EM-level is highlighted here by a careful study on the corresponding disease characteristics of MVID and PFIC. Thorough investigations were performed on samples from a unique disease case of a patient with MYO5B mutations, complemented by selected data from two other relevant cases (all recently described: [ 44 ]). The case documented in detail here is remarkable because the adult patient presents only episodically with symptoms of the digestive system.…”
Mutations in the actin motor protein myosinVb (myo5b) cause aberrant apical cargo transport and the congenital enteropathy microvillus inclusion disease (MVID). Recently, missense mutations in myo5b were also associated with progressive familial intrahepatic cholestasis (MYO5B-PFIC). Here, we thoroughly characterized the ultrastructural and immuno-cytochemical phenotype of hepatocytes and duodenal enterocytes from a unique case of an adult MYO5B-PFIC patient who showed constant hepatopathy but only periodic enteric symptoms. Selected data from two other patients supported the findings. Advanced methods such as cryo-fixation, freeze-substitution, immuno-gold labeling, electron tomography and immuno-fluorescence microscopy complemented the standard procedures. Liver biopsies showed mislocalization of Rab11 and bile canalicular membrane proteins. Rab11-positive vesicles clustered around bile canaliculi and resembled subapical clusters of aberrant recycling endosomes in enterocytes from MVID patients. The adult patient studied in detail showed a severe, MVID-specific enterocyte phenotype, despite only a mild clinical intestinal presentation. This included mislocalization of numerous proteins essential for apical cargo transport and morphological alterations. We characterized the heterogeneous population of large catabolic organelles regarding their complex ultrastructure and differential distribution of autophagic and lysosomal marker proteins. Finally, we generated duodenal organoids/enteroids from biopsies that recapitulated all MVID hallmarks, demonstrating the potential of this disease model for personalized medicine.
“…For EM we analyzed duodenal samples from 2 patients with functional dyspepsia (one of them shown in Figures S1a–c and S4c,f ) and liver samples from one patient with Friedreich’s ataxia (shown in respective text figures), from one patient with alpha-1 antitrypsin deficiency (not shown), and from a healthy donor liver. All three patients MYO5B mutations with were genetically described recently [ 44 ].…”
Section: Resultsmentioning
confidence: 99%
“…Patient #1 is 35-year-old Caucasian male with compound heterozygous MYO5B-mutations: c.242A>G (p.His81Arg) and c.4798C>T (Gln1600*) [ 44 ]. Parental consanguinity is not known.…”
Section: Resultsmentioning
confidence: 99%
“…Patient #2 is a 12-year-old Arab female, daughter of consanguineous parents, with homozygous MYO5B-mutations: c1669G>T (p.Val557Leu) [ 44 ]. Disease onset was reported at 11 months of age with diarrhea and cholestasis.…”
Section: Resultsmentioning
confidence: 99%
“…Thus, the emerging field on MYO5B associated PFIC (MYO5B-PFIC) has focused on liver function and morphology of PFIC6 patients. Concerning MVID, typical intestinal symptoms were not present in several MYO5B-PFIC patients [ 39 , 42 , 44 ]. A detailed subcellular and ultrastructural characterization of the intestine in MYO5B-PFIC patients is lacking as yet.…”
Section: Introductionmentioning
confidence: 99%
“…The specific added value for ultrastructural pathology and more generally for disease-relevant immuno-histochemistry at EM-level is highlighted here by a careful study on the corresponding disease characteristics of MVID and PFIC. Thorough investigations were performed on samples from a unique disease case of a patient with MYO5B mutations, complemented by selected data from two other relevant cases (all recently described: [ 44 ]). The case documented in detail here is remarkable because the adult patient presents only episodically with symptoms of the digestive system.…”
Mutations in the actin motor protein myosinVb (myo5b) cause aberrant apical cargo transport and the congenital enteropathy microvillus inclusion disease (MVID). Recently, missense mutations in myo5b were also associated with progressive familial intrahepatic cholestasis (MYO5B-PFIC). Here, we thoroughly characterized the ultrastructural and immuno-cytochemical phenotype of hepatocytes and duodenal enterocytes from a unique case of an adult MYO5B-PFIC patient who showed constant hepatopathy but only periodic enteric symptoms. Selected data from two other patients supported the findings. Advanced methods such as cryo-fixation, freeze-substitution, immuno-gold labeling, electron tomography and immuno-fluorescence microscopy complemented the standard procedures. Liver biopsies showed mislocalization of Rab11 and bile canalicular membrane proteins. Rab11-positive vesicles clustered around bile canaliculi and resembled subapical clusters of aberrant recycling endosomes in enterocytes from MVID patients. The adult patient studied in detail showed a severe, MVID-specific enterocyte phenotype, despite only a mild clinical intestinal presentation. This included mislocalization of numerous proteins essential for apical cargo transport and morphological alterations. We characterized the heterogeneous population of large catabolic organelles regarding their complex ultrastructure and differential distribution of autophagic and lysosomal marker proteins. Finally, we generated duodenal organoids/enteroids from biopsies that recapitulated all MVID hallmarks, demonstrating the potential of this disease model for personalized medicine.
With the application of modern investigative technologies, cholestatic liver diseases of genetic etiology are increasingly identified as the root cause of previously designated “idiopathic” adult and pediatric liver diseases. Here, we review advances in the field enhanced by a deeper understanding of the phenotypes associated with specific gene defects that lead to cholestatic liver diseases. There are evolving areas for clinicians in the current era specifically regarding the role for biopsy and opportunities for a “sequencing first” approach. Risk stratification based on the severity of the genetic defect holds promise to guide the decision to pursue primary liver transplantation versus medical therapy or nontransplant surgery, as well as early screening for HCC. In the present era, the expanding toolbox of recently approved therapies for hepatologists has real potential to help many of our patients with genetic causes of cholestasis. In addition, there are promising agents under study in the pipeline. Relevant to the current era, there are still gaps in knowledge of causation and pathogenesis and lack of fully accepted biomarkers of disease progression and pruritus. We discuss strategies to overcome the challenges of genotype–phenotype correlation and draw attention to the extrahepatic manifestations of these diseases. Finally, with attention to identifying causes and treatments of genetic cholestatic disorders, we anticipate a vibrant future of this dynamic field which builds upon current and future therapies, real‐world evaluations of individual and combined therapeutics, and the potential incorporation of effective gene editing and gene additive technologies.
BackgroundLong‐term outcomes of congenital diarrheas and enteropathies (CODE) are poorly described. We evaluated the morbidity and mortality of children with CODE followed by an intestinal rehabilitation program (IRP) compared to children with short bowel syndrome (SBS).MethodsMatched case‐control study of children with intestinal failure (IF) due to CODE (diagnosed between 2006 and 2020; N = 15) and SBS (N = 42), matched 1:3, based on age at diagnosis and duration of parenteral nutrition (PN). Nutritional status, growth, and IF‐related complications were compared. Survival and enteral autonomy were compared to a nonmatched SBS cohort (N = 177).ResultsFifteen CODE patients (five males, median age 3.2 years) were followed for a median of 2.9 years. Eleven children were alive at the end of the follow‐up, and two achieved enteral autonomy. The CODE group had higher median PN fluid and calorie requirements than their matched SBS controls at the end of the follow‐up (83 vs. 45 mL/kg/day, p = 0.01; 54 vs. 30.5 kcal/kg/day, p < 0.01), but had similar rates of growth parameters, intestinal failure associated liver disease (IFALD), central venous catheter (CVC) complications and nephrocalcinosis. Kaplan–Meier (KM) analyses of 10‐year survival and enteral autonomy were significantly lower in CODE patients compared to the nonmatched SBS population (60% vs. 89% and 30% vs. 87%, respectively; log‐rank p < 0.008).ConclusionsDespite higher PN needs in CODE, rates of IF complications were similar to matched children with SBS. Enteral autonomy and survival rates were lower in CODE patients. Treatment by IRP can mitigate IF‐related complications and improve CODE patient's outcome.
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