TARDBP and proteostasis deficiencies: Our previous study has shown that iPSC‐derived astrocytes carrying a TARDBP mutation do not display TDP‐43 aggregates or loss of nuclear TDP‐43 despite increased cytoplasmic TDP‐43 expression (Serio et al., 2013), nor do we detect TDP‐43 proteinopathies in astrocytes harboring a C9orf72 mutation in the present study, suggesting that iPSC‐derived astrocytes may not manifest all TDP‐43 proteinopathies in vitro.