Circular RNAs in early brain development and their influence and clinical significance in neuropsychiatric disorders.

Neuropsychiatric disorders represent a set of severe and complex mental illnesses, and the exact etiologies of which are unknown. It has been well documented that impairments in the early development of the brain contribute to the pathogenesis of many neuropsychiatric disorders. Currently, the diagnosis of neuropsychiatric disorders largely relies on subjective cognitive assessment, because there are no widely accepted biochemical or genetic biomarkers for diagnosing mental illness. Circular RNAs (circRNAs) are a novel class of endogenous non-coding RNA (ncRNA) with a closed-loop structure. In recent years, there have been tremendous advances in our understanding of the expression profiles and biological roles of circRNAs. In the brain, circRNAs are particularly enriched and are expressed more abundantly in contrast to linear counterpart transcripts. They are highly active at neuronal synapses. These features make circRNAs uniquely crucial for understanding brain health, disease, and neuropsychiatric disorders. This review focuses on the role of circRNAs in early brain development and other brain-related processes that have been associated with the development of neuropsychiatric disorders. In addition, we discuss the potential for blood or cerebrospinal fluid circRNAs to be used as novel biomarkers in the early diagnosis of neuropsychiatric disorders. The findings reviewed here may provide new insight into the pathological mechanisms underlying the onset and progression of neuropsychiatric disorders.