Inducible neuroblast differentiation into mature neurons reveals centrosome-spliceosome complex as a new splicing-modifying site

Nuclear transcriptional factors are key regulators of stem cell identity and differentiation, however whether extra-nuclear factors are involved in cell fate decisions remains unclear. Here we report that centrosome-associated spliceosome repression drives the differentiation of immature neuroblasts into neurons. Using neuroblastoma cells undergoing asymmetric division (ACD) as a model, we demonstrate that spliceosome components assemble preferentially at the mother centriole and undergo dynamic relocation in response to retinoic acid (RA) or centrosome ablation. ACD cells require selective Ninein splicing variants to promote the efficient formation of centrosome-associated spliceosome condensates. RA-induced neuron differentiation activates ciliogenesis and alternative splicing patterns, including cytoplasmic intron-retained transcripts in spliceosome-related genes. While pharmacological ablation of cilia impedes RA-dependent neuronal differentiation, inhibition of centriole duplication enhances synapse formation, recapitulating the molecular and morphological features of neurons. Mechanistically, centrosome repression-mediated differentiation of ACD cells into neurons relocates spliceosome factors between the nucleus and centrosome, activating cytoplasmic intron retention and exon inclusion in genes essential for ciliogenesis and cerebral cortical development. Collectively, our findings establish a cellular model for programmed splicing control and a strategy to enhance cytoplasmic spliced genes critical for human brain development.