BAG3 and muscular disease: Conversely, mutations in small HSPs such as HSPB1, HSPB3, HSPB5, HSPB8 and the co-chaperones DNAJB6 and BAG3 have all been associated with motor neuron and muscular diseases (Vicart et al., 1998; Selcen et al., 2009; Couthouis et al., 2014).