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Abstract
In mammals, many classes of noncoding RNAs (ncRNAs) are expressed at a much higher
level in the brain than in other organs. Recent studies have identified a new class
of ncRNAs called circular RNAs (circRNAs), which are produced by back-splicing and
fusion of either exons, introns, or both exon-intron into covalently closed loops.
The circRNAs are also highly enriched in the brain and increase continuously from
the embryonic to the adult stage. Although the functional significance and mechanism
of action of circRNAs are still being actively explored, they are thought to regulate
the transcription of their host genes and sequestration of miRNAs and RNA binding
proteins. Some circRNAs are also shown to have translation potential to form peptides.
The expression and abundance of circRNAs seem to be spatiotemporally maintained in
a normal brain. Altered expression of circRNAs is also thought to mediate several
disorders, including brain-tumor growth, and acute and chronic neurodegenerative disorders
by affecting mechanisms such as angiogenesis, neuronal plasticity, autophagy, apoptosis,
and inflammation. This review discusses the involvement of various circRNAs in brain
development and CNS diseases. A better understanding of the circRNA function will
help to develop novel therapeutic strategies to treat CNS complications.