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Advanced Microscopy for Liver and Gut Ultrastructural Pathology in Patients with MVID and PFIC Caused by MYO5B
Michael W Hess1, Iris M Krainer2, Przemyslaw A Filipek2
1Institute of Histology and Embryology, Medical University of Innsbruck, A-6020 Innsbruck, Austria.
Abstract:
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.
Insights
Mutations in myosinVb (myo5b) cause rare liver and intestinal diseases. This study reveals cellular defects in a progressive familial intrahepatic cholestasis patient, highlighting disease mechanisms and a potential model for personalized medicine.
Area of Science:
- Cell Biology
- Genetics
- Gastroenterology
Background:
- Mutations in the actin motor protein myosinVb (myo5b) are linked to microvillus inclusion disease (MVID) and progressive familial intrahepatic cholestasis (PFIC).
- Understanding the cellular basis of MYO5B-PFIC is crucial for developing effective treatments.
Purpose of the Study:
- To thoroughly characterize the ultrastructural and immuno-cytochemical phenotype of hepatocytes and duodenal enterocytes in an adult MYO5B-PFIC patient.
- To investigate the cellular mechanisms underlying MYO5B-PFIC and explore potential disease models.
Main Methods:
- Cryo-fixation, freeze-substitution, immuno-gold labeling, electron tomography, and immuno-fluorescence microscopy.
- Analysis of liver and duodenal biopsies from an adult MYO5B-PFIC patient and two additional patients.
- Generation of duodenal organoids (enteroids) from patient biopsies.
Main Results:
- Hepatocytes showed mislocalization of Rab11 and bile canalicular membrane proteins, with Rab11-positive vesicles clustering around bile canaliculi.
- Duodenal enterocytes exhibited a severe, MVID-specific phenotype with mislocalized apical cargo transport proteins and morphological alterations, despite mild intestinal symptoms.
- Characterization of a heterogeneous population of catabolic organelles with differential distribution of autophagic and lysosomal markers.
- Duodenal organoids recapitulated MVID hallmarks, serving as a disease model.
Conclusions:
- MYO5B mutations lead to significant cellular defects in both hepatocytes and enterocytes, contributing to the complex phenotype of MYO5B-PFIC.
- The study provides detailed ultrastructural and immuno-cytochemical insights into MYO5B-PFIC pathogenesis.
- Patient-derived duodenal organoids offer a promising platform for studying MYO5B-PFIC and developing personalized medicine approaches.
