Neuromyelitis Optica and Nucleotide Variations of Aquaporin-4 Gene

Neuromyelitis opitca (NMO) is an autoimmune disease that relates to deposition of anti-Aquaporin-4 (AQP4) IgG in the central nervous system (CNS). However, called seronegative NMO when patients are negative for AQP4 antibody. Nevertheless, NMO is most probably an antibody mediated disease. The aim of this study was to assess the association between seronegative NMO disease and variations in the AQP4 gene region. A total of 24 seronegative NMO patients were enrolled in the study in 12 months. The frequency of neucleotide variations in 5’ untranslated region (5’-UTR), coding, noncoding, and 3’ untranslated region (3’-UTR) regions were found and compared with the corresponding rates reported previously. The frequencies of the studied variations showed no statistical difference with the rates reported previously. However, a variation was found in 7% of the alleles in the intronic region between exons 1 and 2 which has not been reported so far. Nucleotide variation in different regions of AQP4 gene can affect antigenicity of AQP4 in different ways one of which is making a change in AQP4 isoform (M1/M23) expression ratio. While the variation found in this study in the intronic region of the gene can affect isoform expression ratio, further investigation is needed to determine its role.