MicroRNAs and neurodegeneration: role and impact
ABSTRACT Neurodegenerative diseases are typically late-onset, progressive disorders that affect neural function and integrity. Although most attention has been focused on the genetic underpinnings of familial disease, mechanisms are likely to be shared with more predominant sporadic forms, which can be influenced by age, environment, and genetic inputs. Previous work has largely addressed the roles of select protein-coding genes; however, disease pathogenesis is complicated and can be modulated through not just protein-coding genes, but also regulatory mechanisms mediated by the exploding world of small non-coding RNAs. Here, we focus on emerging roles of miRNAs in age-associated events impacting long-term brain integrity and neurodegenerative disease.
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ABSTRACT: Neurodegenerative diseases, such as frontotemporal dementia (FTD), are often associated with behavioral deficits, but the underlying anatomical and molecular causes remain poorly understood. Here we show that forebrain-specific expression of FTD-associated mutant CHMP2B in mice causes several age-dependent neurodegenerative phenotypes, including social behavioral impairments. The social deficits were accompanied by a change in AMPA receptor (AMPAR) composition, leading to an imbalance between Ca(2+)-permeable and Ca(2+)-impermeable AMPARs. Expression of most AMPAR subunits was regulated by the brain-enriched microRNA miR-124, whose abundance was markedly decreased in the superficial layers of the cerebral cortex of mice expressing the mutant CHMP2B. We found similar changes in miR-124 and AMPAR levels in the frontal cortex and induced pluripotent stem cell-derived neurons from subjects with behavioral variant FTD. Moreover, ectopic miR-124 expression in the medial prefrontal cortex of mutant mice decreased AMPAR levels and partially rescued behavioral deficits. Knockdown of the AMPAR subunit Gria2 also alleviated social impairments. Our results identify a previously undescribed mechanism involving miR-124 and AMPARs in regulating social behavior in FTD and suggest a potential therapeutic avenue.Nature Medicine 11/2014; DOI:10.1038/nm.3717 · 28.05 Impact Factor
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ABSTRACT: Gene transcription produces a wide variety of ribonucleic acid (RNA) species in eukaryotes. Individual types of RNA, such as messenger, structural and regulatory RNA, are known to play distinct roles in the cell. Recently, researchers have identified a large number of RNA-mediated toxicity pathways that play significant pathogenic roles in numerous human disorders. In this article, we describe various common RNA toxicity pathways, namely epigenetic gene silencing, nucleolar stress, nucleocytoplasmic transport, bi-directional gene transcription, repeat-associated non-ATG translation, RNA foci formation and cellular protein sequestration. We emphasize RNA toxicity mechanisms that involve nucleotide repeat expansion, such as those related to polyglutamine (polyQ) disorders and frontotemporal lobar degeneration-amyotrophic lateral sclerosis.Frontiers in Cellular Neuroscience 12/2014; 8:431. DOI:10.3389/fncel.2014.00431 · 4.18 Impact Factor
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ABSTRACT: Elucidating the molecular mechanisms of brain aging remains a significant challenge for biogerontologists. The discovery of gene regulation by microRNAs (miRNAs) has added a new dimension for examining this process; however, the full complement of miRNAs involved in brain aging is still not known. In this study, miRNA profiles of young, adult, and old rats were obtained to evaluate molecular changes during aging. High-throughput deep sequencing revealed 547 known and 171 candidate novel miRNAs that were differentially expressed among groups. Unexpectedly, miRNA expression did not decline progressively with advancing age; moreover, genes targeted by age-associated miRNAs were predicted to be involved in biological processes linked to aging and neurodegenerative diseases. These findings provide novel insight into the molecular mechanisms underlying brain aging and a resource for future studies on age-related brain disorders. Copyright © 2014 Elsevier Inc. All rights reserved.Neurobiology of Aging 11/2014; DOI:10.1016/j.neurobiolaging.2014.11.001 · 4.85 Impact Factor