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Microvillus inclusion disease-causing MYO5B point mutations exert differential effects on motor function
Deanna M Bowman1, Leslie M Meenderink2, Kyra S Thomas3
1Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA; Epithelial Biology Center, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
Abstract:
Microvillus inclusion disease (MVID) is a rare congenital diarrheal disorder typically caused by loss of function mutations in the unconventional myosin, myosin 5b (MYO5B), which leads to the mistrafficking of apical components in enterocytes. MVID can manifest in two phenotypes: in both the intestine and liver or the liver alone. Although previous studies seeking to understand MVID disease pathology used MYO5B KO models, many patients have point mutations and thus express a dysfunctional MYO5B. How these point mutations lead to a broad spectrum of disease severity and the development of two distinct disease phenotypes is still not known. Here, we investigate the effect of MVID patient mutations on the function of the MYO5B motor domain, independent of cargo binding, using confocal imaging and fluorescence recovery after photobleaching. Patient mutations demonstrated a range of effects in these assays, from rigor-like behavior to loss of actin binding. Additionally, analysis of fluorescence recovery after photobleaching turnover kinetics suggests that some mutations negatively impact the ability of MYO5B to stay bound to actin. Collectively, our findings indicate that patient mutations affect the MYO5B motor domain in diverse ways, consistent with the spectrum of phenotypes observed in patients.
Insights
Microvillus inclusion disease (MVID) is a rare diarrheal disorder. Patient mutations in myosin 5b (MYO5B) affect its motor domain function, explaining MVID
Area of Science:
- Cell Biology
- Genetics
- Gastroenterology
Background:
- Microvillus inclusion disease (MVID) is a rare congenital diarrheal disorder.
- It is typically caused by loss-of-function mutations in the unconventional myosin MYO5B, leading to enterocyte mistrafficking.
- MVID presents with distinct phenotypes affecting the intestine and/or liver.
Purpose of the Study:
- To investigate how MVID patient mutations impact the MYO5B motor domain function, independent of cargo binding.
- To understand the molecular basis for the spectrum of MVID disease severity and phenotypes.
Main Methods:
- Utilized confocal imaging and fluorescence recovery after photobleaching (FRAP) assays.
- Examined the effects of patient-derived MYO5B mutations on motor domain function and actin binding.
- Analyzed FRAP turnover kinetics to assess MYO5B-actin interaction stability.
Main Results:
- Patient mutations exhibited diverse effects on MYO5B motor domain function, including rigor-like behavior and impaired actin binding.
- Some mutations were found to reduce the stability of MYO5B binding to actin.
- These functional alterations in the motor domain correlate with the observed spectrum of MVID phenotypes.
Conclusions:
- MVID-associated MYO5B mutations impact the motor domain in various ways.
- These diverse functional effects on MYO5B explain the broad spectrum of disease severity and distinct phenotypes in MVID patients.
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