Given the recent identification of Grp94 and other endoplasmic reticulum (ER) chaperones as potential biomarkers for diagnosis of myasthenia gravis, an autoimmune NMJ disease, results of this study not only enhance our understanding on the fundamental mechanisms underlying NMJ development but also provide insights into the pathogenic mechanisms underlying ER stress response and NMJ disruption in neuromuscular diseases. The gene discussed is HSP90B1; the disease is myasthenia gravis.