(653.5) Resolving the Maturation of Elastomeric Protein Condensates

Poster Board Number: A151

Alfredo Vidal Ceballos (The Graduate Center, CUNY, Advanced Science Research Center, CUNY), Jairo Diaz A. (Rochester Institute of Technology), Jonathan Preston (The City College of New York), Christo Vairamon (The City College of New York), Christopher Shen (The City College of New York), Ronald Koder (The City College of New York, The Graduate Center, CUNY), Shana Elbaum-Garfinkle (The Graduate Center, CUNY, Advanced Science Research Center, CUNY)

Tropoelastin is a key protein in the formation of connective tissue such as lungs, arteries, and cartilage. The assembly and further cross-linking process of tropoelastin culminates in the formation of elastin fibers, a resilient biomaterial capable of withstanding numerous cycles of stress and strain. Like other intrinsically disordered proteins, tropoelastin can undergo liquid-liquid phase separation in vitro and in the extracellular space. This event is thought to aid in the self-assembly and subsequent maturation of elastin fibers. Although the mechanical properties and morphology of mature elastin fibers have been extensively studied, the properties of elastin liquid droplets and their subsequent maturation into a solid remains poorly understood. Here, we use a model mini-elastin polypeptide that mimics the domain architecture of naturally occurring tropoelastin to characterize this transition. We use fluorescence recovery after photobleaching (FRAP) and microrheology to capture the transition of elastin droplets from a liquid to a solid-like state. We find that elastin droplets behave as viscous fluids at early incubation times, however, a rapid liquid-to-solid transition is observed in a timeframe of 80 minutes when held at constant temperature, even in the absence of cross-linker. We further resolve the changes in dynamics, diffusion, and material properties of elastin condensates over the course of this transition. This work, which reveals the material transition from within elastin condensates, lends new insight into the early steps of the self-assembly process of elastin while also contributing to the expanding repertoire of condensate maturation models in biological systems.