Interestingly, the existence of a possible role played by ER stress and UPR modulators in the pathogenesis of clinically relevant conditions such as bipolar disorder and schizophrenia is further highlighted by two other genetic association studies, where mutations or SNPs have been identified in the genes encoding the ER-resident chaperones calreticulin and GRP94/GP96 (Aghajani et al., 2006; Kakiuchi et al., 2007). The gene discussed is HSP90B1; the disease is bipolar disorder.