MIDBODY-MEDIATED REGULATION OF NEURAL STEM CELL SELF-RENEWAL AND DIFFERENTIATION

The midbody is a transient microtubule-rich structure formed during late cytokinesis that coordinates abscission and ensures accurate cell division. Beyond this canonical role, increasing evidence links midbody dynamics to stem cell fate regulation. In embryonic and neural stem cells, midbody retention correlates with stemness, whereas midbody release or degradation accompanies differentiation. During corticogenesis, neural stem cells retain midbodies at the apical membrane early in development, with this behavior declining as neurogenesis proceeds. These observations suggest that the midbody may function as a signaling organelle influencing stem cell identity, yet its molecular composition and regulatory mechanisms in human neural stem cells (hNSCs) remain poorly defined.

To define CEP55-dependent midbody signaling networks, we employed proximity-labeling proteomics using a CEP55-TurboID fusion expressed in hESC-derived human brain organoids. TurboID-mediated biotinylation enabled high-resolution labeling of proteins within ~10 nm of CEP55 during both interphase and mitosis, followed by mass spectrometry–based identification of CEP55-associated proteins. This approach revealed enrichment of pathways involved in cytoskeletal organization, membrane trafficking, intracellular and nucleocytoplasmic transport, neural progenitor proliferation, and neuronal morphogenesis. Notably, CEP55 interactors showed strong enrichment for chromatin-regulatory assemblies, including SWI/SNF (BAF and PBAF) complexes and RNA polymerase II–associated transcriptional regulators. These findings demonstrate that CEP55-linked midbody networks extend beyond cytokinesis to interface with epigenetic and transcriptional machinery, supporting a model in which the midbody actively regulates gene expression programs underlying hNSC self-renewal, fate commitment, and human cortical development.