Actin filament organization in aligned prefusion myoblasts

Understanding how actin filaments are arranged in myoblasts before fusion is important for explaining cell behavior. Prior research has shown that actin structures influence cell shape and movement. However, the specific organization of actin in aligned prefusion myoblasts remains unclear. No prior work had resolved the detailed spatial and polar orientation of these filaments. This gap motivated the current investigation. The study aimed to clarify how actin filaments are arranged in these cells. The researchers focused on whether filament bundles or stress fibers are present. Their work provides new insights into the cytoskeletal structure of these cells.

The purpose of the study was to examine the actin cytoskeleton in prefusion myoblasts. These cells align before fusing to form muscle fibers. The researchers wanted to determine how actin filaments are organized in these cells. They also aimed to assess the polarity of these filaments. The study sought to clarify whether filament bundles exist in this context. The motivation was to understand how actin contributes to cell shape and movement. The researchers used electron microscopy to visualize the filaments. Their findings help explain the structural basis of myoblast alignment.

The researchers used transmission electron microscopy to examine actin filaments in prefusion myoblasts. They analyzed the spatial distribution and orientation of the filaments. The cells were observed in both fixed and live conditions. Time-lapse phase microscopy was used to track cell movement. The team counted filaments in different regions of the cell. They distinguished between subplasmalemma sheets and cytoplasmic filaments. Polarity was assessed by examining the direction of barbed ends. The absence of bundles was confirmed through detailed imaging.

The study found that 84% of actin filaments were in a subplasmalemma sheet or protrusions. These structures aligned with the long axis of the cell. The remaining filaments were randomly oriented in the cytoplasm. The polarity of the subplasmalemma filaments changed along the cell length. At the cell ends and in protrusions, barbed ends pointed toward the tips. No filament bundles or stress fibers were observed. Time-lapse imaging showed active migration along the cell axis. The results suggest that the subplasmalemma sheet supports both shape and movement.

The findings suggest that actin filaments in aligned myoblasts are organized into a subplasmalemma sheet. This sheet contributes to cell shape and movement. The absence of bundles indicates an alternative mechanism for locomotion. The polarity of the filaments varies along the cell length. Protrusions show consistent barbed-end orientation. The study supports the idea that the sheet is functional in migration. The researchers propose that this structure is sufficient for movement. Their results highlight the importance of actin organization in myoblast alignment.