L-bodies are novel RNA-protein condensates driving RNA transport in Xenopus oocytes

RNP granules are membrane-less compartments within cells, formed by phase separation, that function as regulatory hubs for diverse biological processes. However, the mechanisms by which RNAs and proteins interact to promote RNP granule assembly and function in vivo remain unclear. In Xenopus laevis oocytes, maternal mRNAs are transported as large RNPs to the vegetal hemisphere of the developing oocyte, where local translation is critical for proper embryonic patterning. Here, we demonstrate that vegetal transport RNPs represent a new class of cytoplasmic RNP granule, termed Localization-bodies (L-bodies). We show that L-bodies are multiphase RNP granules, containing a dynamic liquid-like protein-containing phase surrounding a non-dynamic RNA-containing substructure. Our results support a role for RNA as a critical scaffold component within these RNP granules and suggest that cis-elements within localized mRNAs may drive subcellular RNA localization through control over phase behavior. Overall design: 4 replicates of 3 conditions were analyzed, the conditions being RNA collected after immunoprecipitating Xenopus oocyte lysates with different antibodies. The experimental conditions were precipitated with Staufen and hnRNPab antibodies and the control condition precipitated with IgG.