Myasthenia gravis (MG) is a T-dependent B-cell mediated autoimmune disorder characterized by impaired neuromuscular transmission, resulting in muscular weakness and fatigability. In most of the patients (over 80%) the disease is caused by autoantibodies against the acetylcholine receptor (AChR). Several lines of evidence indicate that the thymus is the main site of the autosensitization process in AChR-MG patients, who frequently undergo symptom remission after thymectomy. However, the exact immunological mechanisms underlying the autoimmune response are still unknown. We are exploiting next-generation sequencing approaches: 1. to compare TCR and BCR repertoires between MG patients and controls, and 2. to identify a molecular signature of the disease in peripheral blood of MG patients. We found that CDR3 amino acid length distribution was different from controls in 4 out of 12 MG patients, suggesting a possible clinical relevance. We are currently further analyzing the data and the correlation with the disease.
RNA deep sequencing combined with Ingenuity Pathway Analysis (IPA) revealed that 128 genes and 9 microRNA precursors were differentially expressed between MG patients and controls. By qPCR, we found that five microRNAs (i.e. miR-612, miR-1299, miR-3651, miR-3654 and miR-4426) were up-regulated in MG patients compared to controls. NanoString technology validated the predicted differentially expressed miRNA-target genes. Interestingly, anti-correlation of the expression levels was found between the up-regulated miR-612 and miR-3651 and down-regulated target genes. Furthermore, functional annotation performed by IPA showed that 17% (22 out of 128) of the differentially expressed genes were associated with viral infections. Some of them were selected and validated, thus suggesting that in MG patients an alteration in anti-viral responses might occur. We will discuss our findings with the aim of better understanding the molecular basis of MG pathogenesis.