This study investigates how biomolecular condensates affect the aggregation of disease-associated repeat RNAs in neurological disorders. We demonstrate that these RNAs undergo an age-dependent transition within condensates to form solid clusters, creating multiphasic structures with RNA-rich cores surrounded by RNA-depleted fluid shells. The timing of this clustering process depends on RNA sequence, structure stability, and repeat length. Notably, the stress granule protein G3BP1 counteracts this aberrant RNA clustering. Our findings suggest biomolecular condensates can serve as sites for pathological RNA aggregation while highlighting how RNA-binding proteins may protect against these harmful transitions.

This study introduces EXO-Probe, a novel RNA-based biomaterial that combines an EV-loading sequence with a fluorogenic RNA Mango aptamer to enable visualization and tracking of RNA within extracellular vesicles. Our technology allows non-destructive quantification of EVs and investigation of RNA trafficking to multivesicular bodies and extracellular vesicles. EXO-Probe provides a valuable tool for studying the role of RNA in EV-mediated cellular communication and has potential applications in enhancing EVs as therapeutic delivery vehicles.

This study reveals how ion concentration gradients in cellular environments drive the formation and transport of biomolecular condensates through diffusiophoresis. Using microfluidic experiments, we demonstrate that these gradients accelerate biomolecule transport, promote location-specific condensate formation, and impart directional motility to condensates. The interplay between gradient-induced movement and reentrant phase behavior extends condensate lifetimes through dynamic redistribution. Our findings establish diffusiophoresis as a critical non-equilibrium force governing biomolecular condensate dynamics in heterogeneous cellular environments.

This study examines how protein sequence determines the viscoelastic properties and aging dynamics of condensates formed by the prion-like domain of hnRNP A1 and its variants. We demonstrate that these condensates begin as metastable Maxwell fluids, with aromatic interactions controlling their initial viscoelastic properties. Over time, they undergo sequence-dependent aging into non-fibrillar, β-sheet-rich semi-crystalline solids. Our findings suggest that evolutionary selection of protein sequences likely balances the metastability of fluid condensates against conversion to stable solid states on biologically relevant timescales.

This study introduces a computational approach for directly calculating the viscoelastic properties of biomolecular condensates by extending the Rouse model to incorporate sequence-specific molecular interactions. We demonstrate that accurate predictions require accounting for both intra- and inter-chain contacts, confirming that condensates behave as generalized Maxwell fluids with continuous relaxation time distributions. Our method enables the inverse calculation of relaxation time spectra from complex shear moduli, providing a valuable complement to emerging experimental microrheology techniques for characterizing condensate dynamics.

Determinants of viscoelasticity and flow activation energy in biomolecular condensates: Alshareedah, I., Singh, A., Yang, S., Ramachandran, V., Quinn, A., Potoyan, D. A., Banerjee, P. R. Science Advances, 16 Feb 2024, Vol 10, Issue 7, doi: 10.1126/sciadv.adi6539 Link to the Paper

This review examines the critical role of RNAs in driving phase separation within biomolecular condensates, shifting focus from the traditionally protein-centric view of these structures. We highlight recent advances in understanding how RNA molecules contribute to condensate formation, regulation, and function in both normal cellular processes and disease states. The review also explores promising research directions that could reveal RNA condensates' role in spatiotemporal cellular regulation and inspire new RNA-based therapeutic approaches.

This study reveals that multiple disordered domains in the mammalian SWI/SNF complex possess prion-like properties with inherent phase separation capabilities. We demonstrate that these domains engage in specific heterotypic interactions with the prion-like domain of FUS, forming co-condensates even under dilute conditions. This positive cooperativity between heterotypic prion-like domains appears to drive the selective co-recruitment of chromatin remodelers with specific transcription factors, providing insight into how oncogenic FET fusion proteins may hijack normal chromatin regulation.