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Myosin-Specific Adaptations of In vitro Fluorescence Microscopy-Based Motility Assays
Published on: February 4, 2021
Smooth-muscle contraction without smooth-muscle myosin
I Morano1, G X Chai, L G Baltas
1Max Delbrück Center for Molecular Medicine (MDC), Robert-Rössle-Strabe 10, D-13092 Berlin, Germany.
Nature Cell Biology
|June 15, 2000
Summary
Smooth-muscle myosin heavy chain is crucial for neonatal mouse bladder function, enabling a transient high-force state. Its absence shifts function to non-muscle myosin, impacting survival and growth.
Area of Science:
- Physiology
- Molecular Biology
- Developmental Biology
Background:
- Smooth muscle contraction relies on myosin heavy chains.
- Two main types exist: smooth-muscle myosin heavy chain (SM-MHC) and non-muscle myosin heavy chain (NM-MHC).
- The specific roles of SM-MHC in neonatal smooth muscle function and survival are not fully understood.
Purpose of the Study:
- To investigate the role of smooth-muscle myosin heavy chain (SM-MHC) in neonatal mouse bladder smooth muscle.
- To determine the contribution of SM-MHC to force generation and shortening velocity.
- To assess the impact of SM-MHC elimination on neonatal survival and growth.
Main Methods:
- Gene targeting was used to eliminate SM-MHC expression in mice (knockout).
- Intact bladder preparations from wild-type and knockout neonatal mice were subjected to KCl depolarization.
- Force generation and maximal shortening velocity were measured during sustained activation.
Main Results:
- SM-MHC knockout mice survived for approximately three days.
- Wild-type bladders exhibited a two-phase response: an initial high-force transient state (phase 1) followed by a sustained low-force state (phase 2).
- Knockout bladders lacked phase 1 but showed a normal phase 2, indicating reliance on NM-MHC.
Conclusions:
- Neonatal smooth muscle phase 1 is primarily mediated by SM-MHC.
- Phase 2 can be supported by NM-MHC.
- SM-MHC is essential for neonatal survival, growth, homeostasis, and circulation shortly after birth.
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