Laureline JULIEN and KELLY MOLNAR

Laureline JULIEN

Drivers for transport in the gastrovascular network of Aurelia Aurita jellyfish

The jellyfish Aurelia aurita possesses a gastrovascular network responsible for digestion and nutrient transport throughout the organism. In the absence of a heart, with an open circulatory system and no smooth muscles lining the canals, the question arises: how is internal fluid flow maintained? Two main hypotheses have been proposed—ciliary-driven transport and peristaltic movements. Initial observations by Southward pointed to ciliary currents, a finding confirmed by our in vivo imaging of active cilia within the jellyfish’s canals. The beating of the cilia generates directed flow and leads to measurable particle displacement, suggesting an active transport mechanism. To further characterize ciliary-driven flow, we combine analyses of ciliary beating patterns with rheological measurements of the canal fluid. As in many biological systems, transport likely results from a cooperative interaction between cilia and mucus. In addition, during swimming, the canals undergo rhythmic longitudinal compression and elongation, indicating that a length imposed peristaltic motion may also contribute. Finally, we address the coexistence of these two transport mechanisms. Our observations suggest an interplay that may reflect an adaptive strategy for efficient internal transport in the absence of centralized pumping.

Kelly Molnar

CDC42 Regulates Golgi Mechanics and Cargo Transport and Organelle Stiffness

The Golgi apparatus functions as a central hub for protein processing and trafficking, yet the contribution of its mechanical properties to cargo transport remains poorly understood. Here, we investigate how the GTPase CDC42 regulates Golgi mechanics and transport dynamics through the actin cytoskeleton. Using a battery of common and cutting edge techniques in cell and membrane biophysics, we investigate the interplay between the different Golgi layers, CDC42, Golgi physics, and cell function.