A Mitochondrial tRNA Mutation Causes Axonal CMT in a Large Venezuelan Family.

OBJECTIVE: The objective of this study was to identify the genetic cause for progressive peripheral nerve disease in a Venezuelan family. Despite the growing list of genes associated with Charcot-Marie-Tooth disease, many patients with axonal forms lack a genetic diagnosis. METHODS: A pedigree was constructed, based on family clinical data. Next-generation sequencing of mitochondrial DNA (mtDNA) was performed for 6 affected family members. Muscle biopsies from 4 family members were used for analysis of muscle histology and ultrastructure, mtDNA sequencing, and RNA quantification. Ultrastructural studies were performed on sensory nerve biopsies from 2 affected family members. RESULTS: Electrodiagnostic testing showed a motor and sensory axonal polyneuropathy. Pedigree analysis revealed inheritance only through the maternal line, consistent with mitochondrial transmission. Sequencing of mtDNA identified a mutation in the mitochondrial tRNAVal (mt-tRNAVal ) gene, m.1661A>G, present at nearly 100% heteroplasmy, which disrupts a Watson-Crick base pair in the T-stem-loop. Muscle biopsies showed chronic denervation/reinnervation changes, whereas biochemical analysis of electron transport chain (ETC) enzyme activities showed reduction in multiple ETC complexes. Northern blots from skeletal muscle total RNA showed severe reduction in abundance of mt-tRNAVal , and mildly increased mt-tRNAPhe , in subjects compared with unrelated age- and sex-matched controls. Nerve biopsies from 2 affected family members demonstrated ultrastructural mitochondrial abnormalities (hyperplasia, hypertrophy, and crystalline arrays) consistent with a mitochondrial neuropathy. CONCLUSION: We identify a previously unreported cause of Charcot-Marie-Tooth (CMT) disease, a mutation in the mt-tRNAVal , in a Venezuelan family. This work expands the list of CMT-associated genes from protein-coding genes to a mitochondrial tRNA gene. ANN NEUROL 2020;88:830-842.

Diagnostic value of miR-145 and its regulatory role in macrophage immune response in tuberculosis.

Tuberculosis (TB) induced by Mycobacterium tuberculosis (Mtb) is a serious global health burden. This study sought to investigate the expression and diagnostic value of serum miR-145 in TB patients and explore the biological function of miR-145 using macrophages. Serum expression levels of miR-145 were estimated by quantitative real-time PCR. A receiver operating characteristic curve was plotted to evaluate the diagnostic accuracy of miR-145. This study further focused on the effects of miR-145 on cell viability and inflammation in macrophages upon Mtb infection, and explored the potential target gene of miR-145. Serum expression levels of miR-145 were decreased in TB patients, and the upregulated inflammatory cytokines in TB patients were negatively correlated with the serum expression levels of miR-145. miR-145 had considerable diagnostic accuracy in distinguishing of TB patients from healthy individuals and differentiating between active TB cases and latent TB cases. Mtb infection induced an increase in cell viability and inflammatory responses in macrophages, but these promoting effects were rescued by the overexpression of miR-145. CXCL16 was determined as a target gene of miR-145 in macrophages. Overall, this study demonstrated that the decreased serum miR-145 expression serves a candidate diagnostic biomarker in TB patients. The overexpression of miR-145 in macrophages upon Mtb infection can suppress cell viability and infection-induced inflammation via regulating CXCL16, indicating the potential of miR-145 as a therapeutic target of TB.