As LC domains contain a large number of charged residues, phase separation is necessarily induced by charged residues or charged regions (as discussed previously). For example, LC domains and disordered positively charged RGG (Arginine-Glycine-Glycine) repeats are present in many RBPs. P granules in C. elegans are formed by the LAF-1 RBP in vivo. RGG repeat regions present in LAF-1 that can be separately isolated from the entire protein can phase separate in vitro, suggesting that the entire LAF-1 protein is not an ad hoc requirement for phase separation. Thus, RGG domains from LAF-1 have been modified to engineer switchable phase-separated reversible compartmentalization systems in vitro that can assemble/disassemble and recruit/release biomolecules with the help of specific biochemical reactions. Similarly, CIRBP (an RBP) recombinants containing only the RGG domain can also phase separate upon RNA binding without the necessity of the entire protein in vitro. These RGG repeats are also present in FUS family proteins and are critical for the formation of stress granules. Hybrids containing LC domains of FUS (containing the RGG domains) as stickers and dextran polymers as spacers (replicating the stickerspacer arrangement of modern IDPs) can also phase separate in vitro, suggesting the importance of the RGG motif in phase separation. In fact, RGG domains are highly conserved, and have been hypothesized