Noncoding RNAs are widely known for their various essential roles in the development of central nervous system. It involves neurogenesis, neural stem cells generation, maintenance and maturation, neurotransmission, neural network plasticity, formation of synapses, and even brain aging and DNA damage responses. In this review, we will discuss the biogenesis of microRNA, various functions of noncoding RNA's specifically microRNAs (miRNAs) that act as the chief regulators of gene expression, and focus in particular on misregulation of miRNAs which leads to several neurodegenerative diseases as well as its therapeutic outcome. Recent evidences has shown that miRNAs expression levels are changed in patients with neurodegenerative diseases; hence, miRNA can be used as a potential diagnostic biomarker and serve as an effective therapeutic tool in overcoming various neurodegenerative disease processes. 1. Introduction Genetic and environmental factors can contribute to the development of neurodegenerative diseases. Recent studies demonstrate roles for regulatory noncoding RNA molecules (ncRNAs) in normal CNS development and function and in the onset and progression of various neurodegenerative diseases. ncRNAs are functional RNA molecules expressed specifically in the central nervous system that do not encode proteins. They are classified as small ncRNAs comprising fewer than 400 nucleotides and long ncRNAs comprising more than 400 nucleotides. Small ncRNAs include ribosomal RNAs (rRNAs), transfer RNAs (tRNAs), small nucleolar RNAs (snRNAs), microRNAs (miRNAs), short small interference RNAs (siRNAs), and piwi-interacting RNAs. Long noncoding RNAs (lncRNAs) include heterogeneous regulatory molecules such as long intergenic noncoding RNAs (linc RNAs) and natural antisense transcripts (NATs) [1–3]. ncRNAs play critical roles in neuronal processes such as transcription of neuronal genes, brain morphogenesis, neuronal cell specification, and formation of memory [3]. 2. Biogenesis of MicroRNAs MicroRNAs (miRNAs) are small RNA molecules (21–23 nucleotides) involved in the regulation of gene expression that bind posttranscriptionally to the 3′-untranslated region of target mRNAs and either inhibit translation or degrade the target mRNA [4]. A single-stranded RNA, miRNA, is derived from a 70–100-nucleotide hairpin precursor called pre-miRNA that plays a key role in posttranscriptional regulation of target gene expression. Due to their small size, miRNAs are potentially a valuable tool for therapy of cancer, neurodegenerative, and cardiovascular diseases [5, 6]. The
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