mRNA selectivity of mRNPs appears to be a property of RBPs, as hydrogel formed from purified low-complexity sequence domains of FUS, an RBP associated with the pathogenesis of amyotrophic lateral sclerosis (ALS), preferentially binds to known mRNA components of mRNP granules in neurons— mRNAs with long 3′-UTRs (Han et al., 2012). Here, FUS is linked to amyotrophic lateral sclerosis.