PiWi RNA in Neurodevelopment and Neurodegenerative Disorders

The discovery of the mysterious dark matter of the genome expands our understanding of modern biology. Beyond the genome, the epigenome reveals a hitherto unknown path of key biological and functional gene control activities. Extraordinary character-P element wimpy testis-induced (PiWi)-interacting RNA (piRNA) is a type of small non-coding RNA that acts as a defender by silencing nucleic and structural invaders. PiWi proteins and piRNAs can be found in both reproductive and somatic cells, though germ line richness has been partially unravelled. The primary function is to suppress invading DNA sequences known as Transpose of Elements (TEs) that move within genomic DNA and downstream target genes via Transcriptional Gene Silencing (TGS) and Post-Translational Gene Silencing (PTGS). Germline piRNAs preserve genomic integrity, stability, sternness, and influence imprinting expression. The novel roles of somatic tissue-specific piRNAs have surprised researchers. In metazoans, including humans, piRNA regulates neurodevelopmental processes. The PiWi pathway regulates neural heterogeneity, neurogenesis, neural plasticity, and transgenerational inheritance of adaptive and long-term memory. Dysregulated piRNA causes neurodevelopmental, neurodegenerative, and psychiatric illness. A faulty piRNA signature results in inadvertent gene activation via TE activation, incorrect epigenetic tags on DNA, and/or histones. Imprinting expression is influenced by germline piRNAs, which maintain genomic integrity, stability, and sternness. New roles for piRNAs specific to somatic tissues have been discovered. Metazoans, including humans, are regulated by piRNA. In addition, the PiWi pathway regulates neuronal heterogeneity and neurogenesis as well as brain plasticity and transgenerational inheritance of adaptive and long-term memory. When piRNA is dysregulated, it can lead to neurodegenerative and psychiatric illnesses. Inappropriate gene activation or inactivation is caused by aberrant piRNA signatures, TE activation, inappropriate epigenetic marks on DNA, and/or histones. Defective piRNA regulation causes abnormal brain development and neurodegenerative aetiology, which promotes life-threatening disorders. Exemplification of exciting roles of piRNA is still in its early stages, so future research may expand on these observations using novel techniques and launch them as potential biomarkers for diagnostics and therapeutics. In this review, we summarised the potential gene molecular role of piRNAs in regulating neurobiology and serving as novel biomarkers and therapeutic targets for life-threatening disease.