Organisms that do not maintain a constant body temperature must have some mechanism to adapt their physiological functions in order to survive at a range of temperatures. For individual cells within the organism, the cellular membrane serves as a platform for cellular signaling and cell-cell interaction. The organization and physical properties of plasma membrane lipids are sensitive to changes in temperature. When giant plasma membrane vesicles (GPMVs)— derived from cells grown in culture— are cooled slightly below growth temperature, they separate into distinct ordered and disordered liquid phases. These phases can be observed through fluorescence imaging of a phase-selective dye. ZF4 cells, derived from zebrafish, can be adapted to grow at a range of temperatures and GPMVs derived from these cells were used in our study to examine how these cells change the makeup of their plasma membranes to adapt to changes in temperature.
The cover image of the September 19th issue of Biophysical Journal focuses on an imagined “zebrafish,” which was composed of a fluorescence image of a ZF4-derived GPMV with stripe-like phase separated domains, combined with photographs of a zebrafish and a zebra. These three images were blended together in Photoshop to create our chimeric zebrafish. In this cover image, we wanted to highlight the idea that lipid organization of the plasma membrane could be central to the physiology and function of the organism as a whole. For this reason, we used the fluorescence image of the phase-separated GPMV as the focal point of our “zebrafish,” and used the common visual motif of stripes to draw a comparison between the organization at the sub-cellular level of plasma membrane lipids to the organization at the level of the whole organism. This zebrafish swims through a sea of phase-separated GPMVs, shown in the background, again highlighting the theme of lipid organization.
Projects exploring how the physical properties of the plasma membrane impact membrane organization and function are ongoing in the Veatch Laboratory. This interest applies to a variety of biological processes, from immunoreceptor function to general anesthesia.
– Margaret Burns, Kathleen C. Wisser, Jing Wu, Ilya Levental, Sarah Veatch