TIA1 is involved in stress granule (SG) formation and participates in direct physical or RNA-dependent association with TDP-43 in SGs. TIA1 mutations identified in ALS increase its phase separation propensity, disrupt the normal disassembly of SGs and promote the accumulation of non-dynamic SGs containing the TDP-43 protein. Here, TIA1 is linked to amyotrophic lateral sclerosis.