Furthermore, the delA3 include the substitution at Asp69 that have been previously reported as the most sensitive residue in the extracellular loop A as it impaired AQP4-IgG binding in 93 % of NMO patient sera [13] and produced a significant loss of binding for all loop A-dependent rAbs [14]. The gene discussed is AQP4; the disease is neuromyelitis optica.