DNA Code Unraveled for Rare Neurologic Disease

The team meta-analyzed whole-genome sequences from 86 NMO cases and 460 controls with genome-wide single nucleotide polymorphism (SNP) array from 129 NMO cases and 784 controls to test for association with SNPs and copy number variation (total 215 NMO cases, 1,244 controls).

The investigators determined anti-aquaporin 4 (AQP4) serostatus via standardized assays, including enzyme-linked immunosorbent assay (ELISA) or cell-based assay (CBA). ELISA-based detection was obtained from one of the numerous laboratories that offer the test. CBAs were obtained from the Mayo Clinic Laboratories (Rochester, MN, USA). The team also obtained DNA from 144 NMO cases (78 NMO-immunoglobulin G (IgG)+ / 68 NMO-IgG−). Sequence reads were processed and aligned to a reference genome. Other techniques were used to support the study.

The team identified two independent signals in the major histocompatibility complex (MHC) region associated with NMO-IgG+, one of which may be explained by structural variation in the complement component four genes. Mendelian Randomization analysis revealed a significant causal effect of known systemic lupus erythematosus (SLE), but not multiple sclerosis (MS), risk variants in NMO-IgG+.

Benjamin Greenberg, MD, a neurologist and a senior author of the study, said, “This outcome shows that doing in-depth studies pays off, and more studies like this may be needed to find the problem behind other rare conditions. By taking a rare disease and doing more than just reading every third or fourth page of genetic code, we have modeled NMO in a much more accurate way.” The study was published on May 16, 2018, in the journal Nature Communications.

Related Links:
Broad Institute
Mayo Clinic Laboratories