We have a new paper that just appeared online!
Active Mechanics Reveal Molecular-Scale Force Kinetics in Living Oocytes
Active diffusion of intracellular components is emerging as an important process in cell biology. This process is mediated by complex assemblies of molecular motors and cytoskeletal filaments that drive force generation in the cytoplasm and facilitate enhanced motion. The kinetics of molecular motors have been precisely characterized in vitro by single molecule approaches, but their in vivo behavior remains elusive. Here, we study the active diffusion of vesicles in mouse oocytes, where this process plays a key role in nuclear positioning during development, and combine an experimental and theoretical framework to extract molecular-scale force kinetics (force, power stroke, and velocity) of the in vivo active process. Assuming a single dominant process, we find that the nonequilibrium activity induces rapid kicks of duration τ ∼ 300 μs resulting in an average force of F ∼ 0.4 pN on vesicles in in vivo oocytes, remarkably similar to the kinetics of in vitro myosin-V. Our results reveal that measuring in vivo active fluctuations allows extraction of the molecular-scale activity in agreement with single-molecule studies and demonstrates a mesoscopic framework to access force kinetics.
Congrats to Corbyn, Hunter, and Mauricio for all receiving the Dan Black Fellowship!
Congratulations to both Monika and Paris for being accepted to a prestigious international REU program with France! Monika will be working on cell biophysics and Paris will be working on quantum mechanical oscillators.
Congratulations to both Danielle and Monika for receiving the “Outstanding Presentation Award” at the APS Future of Physics Days!
Small-scale displacement fluctuations of vesicles in fibroblasts
(Submitted on 15 Mar 2018)
The intracellular environment is a dynamic space filled with various organelles moving in all directions. Included in this diverse group of organelles are vesicles, which are involved in transport of molecular cargo throughout the cell. Vesicles move in either a directed or non-directed fashion, often depending on interactions with cytoskeletal proteins such as microtubules, actin filaments, and molecular motors. How these proteins affect the local fluctuations of vesicles in the cytoplasm is not clear since they have the potential to both facilitate and impede movement. Here we show that vesicle mobility is significantly affected by myosin-II, even though it is not a cargo transport motor. We find that myosin-II activity increases the effective diffusivity of vesicles and its inhibition facilitates longer states of non-directed motion. Our study suggests that altering myosin-II activity in the cytoplasm of cells can modulate the mobility of vesicles, providing a possible mechanism for cells to dynamically tune the cytoplasmic environment in space and time.
The whole lab had a great time at the APS March Meeting in LA this year. You can find our posters here: https://slam-lab.com/media-2/posters/
Congratulations to Monika for being an CSUF Edison Scholar!