Stress Granules and FUS condensates recruit functionally distinct sets of RNAs

Cellular homeostasis relies on the organization of RNA and protein into membrane-less organelles. Stress granules (SGs) are well-known hubs for translational repression during cellular stress. Similar condensates formed by RNA-binding proteins such as FUS, mutations in which cause amyotrophic lateral sclerosis (ALS), remain poorly characterized relative to canonical SGs. Here, we develop Granule-seq, a microcapillary-based granule-resolved RNA sequencing approach, and demonstrate that SGs and FUS condensates are functionally distinct RNA compartments rather than variants of a unified granule class. Granules were individually aspirated, analyzed in small pooled sets, and validated through overlap with known SG components (794/2,759 genes, 28.8%, p < 0.001). Gene Ontology analysis revealed that G3BP-positive SGs sequester transcripts for stress responses and translational control, while FUS condensates are enriched for transcripts essential for synaptic function and neuronal development. Direct comparison showed that 63% of FUS-enriched and 82% of G3BP-enriched genes were granule-specific, with only 493 genes shared. Exploratory sequence analysis revealed modest contributions from compositional features, with functional identity providing primary selectivity. As a proof-of-concept study with limited biological replication, our results suggest that distinct granule identities are established through functionally specialized transcriptomes, a process that may be disrupted in ALS, and provide a framework for understanding RNA sorting.