Potential contribution of novel single nucleotide variants to neurodegeneration in MS (P2.218)

OBJECTIVE:To analyze the molecular consequence of single nucleotide variants (SNVs) in the pathogenesis of neuronal death and neurodegeneration in multiple sclerosis (MS). BACKGROUND: Genome Wide Association Studies uncovered important inherited single nucleotide polymorphisms (SNPs) in MS patients, which showed that the SNPs were related to immune regulation. In contrast, analyses of acquired mutations (SNVs) in MS are largely unknown. Because MS patients develop antibodies to heterogeneous nuclear ribonuclear protein A1 (hnRNP A1 - an RNA binding protein), we hypothesized MS patients would contain SNVs in the genomic DNA sequence of hnRNP A1. DESIGN/METHODS:High fidelity DNA sequencing was used to examine the sequence of hnRNP A1 in human brain and lymphocytes. Mutant and wild type hnRNP A1 were transfected into SKNSH neurons and examined for transportin binding, stress granules and apoptosis. Double-label immunocytochemistry was used to localize hnRNP A1 in neurons of brain. RESULTS:Healthy controls (n=7) showed no SNVs in the transportin binding domain of hnRNP A1-‘M9’ (‘M9’ is the RNA transport sequence of hnRNP A1, which binds transportin). In contrast, all primary progressive MS (PPMS) patients (n=4) had at least one SNV in this region. Only one relapsing remitting (n=5) or secondary progressive (n=5) MS patient each had an SNV. Transfection of mutant SNVs in SKNSH cells resulted in decreased transportin binding, mis-localization of hnRNP A1 from the nucleus to the cytoplasm, stress granule formation and apoptosis. In contrast to controls, in MS brains there were SNVs and hnRNP A1 mis-localized to the neuronal cytoplasm. CONCLUSIONS:Mutant SNVs in hnRNP A1-M9 DNA were identified in the lymphocytes and brains of MS patients, which when transfected, expressed markers of neuronal dysfunction, suggesting that dysfunction of hnRNP A1 as a result of acquired genetic mutation contributes to neurodegeneration in MS. Study Supported by: Research Service, Department of Veterans Affairs. UTHSC MS Fund. Disclosure: Dr. Levin has received personal compensation for activities with EDM Serono Inc., Teva Neuroscience, Biogen Idec, Gerson Lehman Group and The CME Institute as a speaker and/or consultant. Dr. Lee has nothing to disclose.