# piRNA: Molecular Mechanisms from Germline Silencing to Somatic Regulation and Roles in Disease

## TL;DR

This review explores piRNAs, small RNA molecules that protect the genome in germline cells and also regulate gene activity in other tissues, and their roles in various diseases.

## Contribution

The paper systematically summarizes piRNA biogenesis and their functional diversification from germline to somatic cells.

## Key findings

- piRNAs and PIWI proteins are broadly expressed in somatic tissues and regulate gene expression.
- piRNA dysregulation is linked to cancer, cardiovascular disorders, and neurodegenerative diseases.
- piRNAs show potential as biomarkers and therapeutic targets in disease.

## Abstract

PIWI-interacting RNAs (piRNAs) are a class of small non-coding RNAs initially identified in germline cells as genome guardians that silence transposable elements. Recent studies have expanded this view, revealing that piRNAs and PIWI proteins are broadly expressed in somatic tissues and participate in epigenetic and post-transcriptional gene regulation. This review systematically summarizes piRNA biogenesis and molecular mechanisms, with a focus on their functional diversification from germline to somatic cells. We detail piRNA dysregulation and its association with various human diseases, including cancer, cardiovascular disorders, neurodegenerative diseases, immune dysfunction, and reproductive disorders. By integrating recent findings, this review provides a comprehensive overview of piRNA-mediated regulatory networks and highlights their potential as novel biomarkers and therapeutic targets.