DNAJB6 and proteostasis deficiencies: Phenylalanine mutations in the (G/F)-rich region of MRJ are found in LGMD and distal myopathy, indicating that the chaperone activity of MRJ is critical for preventing proteinopathy (Harms et al., 2012; Sarparanta et al., 2012; Li et al., 2016; Jonson et al., 2018).