T cells specific for aquaporin 4, the major antigen of NMO, cross-react with the homologous ABC transporter peptide of Clostridium perfringens, suggesting that molecular mimicry against microbial antigens could induce the autoimmune response in NMO (Varrin-Doyer et al., 2012). This evidence concerns the gene ABCG2 and neuromyelitis optica.