Analysis of P granules in vivo and ex vivo

Corrected version -This version can be cited . RNA granules are dynamic sub-cellular compartments that lack enveloping membranes. RNA granules have been proposed to form by liquid-liquid phase separation, a thermodynamic process that partitions molecules between dilute and condensed liquid phases 1 . P granules are archetypal RNA granules in C. elegans that display liquid-like behaviors 2 . Here we describe in vivo and ex vivo approaches to analyze the material properties of P granules. We find that the liquid phase of P granules is stabilized by a molecularly-distinct, enveloping shell that is intrinsically non-dynamic. Consistent with a gel phase, the shell is resistant to dilution, high salt, and aliphatic alcohols, and dissolves in SDS. Solidification of RNA granules has been linked to neuronal degeneration 3 . Our findings suggest that gel-like polymers are essential components of RNA granules that help stabilize liquid phases in the cellular environment.