Intron detention tightly regulates the stemness/differentiation switch in the adult neurogenic niche

The adult mammalian brain retains some capacity to replenish neurons and glia, holding promise for brain regeneration. Thus, understanding the mechanisms controlling adult neural stem cell (NSC) differentiation is crucial. Paradoxically, adult NSCs in the subependymal zone transcribe genes associated with both multipotency maintenance and neural differentiation, but the mechanism that prevents conflicts in fate decisions due to these opposing transcriptional programmes is unknown. Here we describe intron detention as such control mechanism. In NSCs, while multiple mRNAs from stemness genes are spliced and exported to the cytoplasm, transcripts from differentiation genes remain unspliced and detained in the nucleus, and the opposite is true under neural differentiation conditions. We also show that m 6 A methylation is the mechanism that releases intron detention and triggers nuclear export, enabling rapid and synchronized responses. m 6 A RNA methylation operates as an on/off switch for transcripts with antagonistic functions, tightly controlling the timing of NSCs commitment to differentiation. mRNAs associated with differentiated cells are already detected in adult neural stem cells. Here the authors show how intron detention prevents their translation, solving conflicts in fate decisions while priming stem cells for timely differentiation.