Intron Retention, an Orchestrated Program of Gene Expression Regulation

Intron retention (IR), a well-conserved form of alternative splicing, is widespread among eukaryotic organisms. It serves as an orchestrated program for regulating gene expression. A previously reported role of IR is to induce intron-retained transcript (IRT) degradation via the nonsense-mediated mRNA decay (NMD) pathway, resulting in the downregulation of gene expression. However, accumulating evidence indicates that most IRTs are detained in the nucleus, and thus, IR can downregulate gene expression through the storage of IRTs in the nucleus. Although the importance of IRTs in gene expression regulation is well established, the detailed mechanisms remain unclear. Here, we propose a potential model to explain how IRTs are retained in the nucleus and respond to environmental changes or developmental transitions. Plenty of future studies are still ahead of us to fully dissect the biological function of IR and the underlying mechanisms.