Dynamin 2–dependent endocytosis differentially regulates ligand and receptor contributions to Notch signaling during neural precursor cell fate determination

Abstract

A critical event in the development of the highly structured cerebral cortex is the appropriate generation of differentiated daughter cell populations from asymmetric precursor cell divisions. Internalization of extracellular receptors and ligands in the process of endocytosis is key to the establishment of asymmetry. However, the detailed mechanisms mediating this exchange are incompletely understood. The dynamin family of membrane remodeling GTPases is considered critical for many forms of clathrin-mediated endocytosis (CME) but its role in brain development is unexplored. Here we found that dynamin 2 (Dnm2), a protein involved in CME through vesicle release from the plasma membrane, is essential for the maintenance of neural stem cells. Conditional deletion of Dnm2 leads to early exhaustion of neural precursor cells and premature neurogenesis, resulting in gross structural abnormalities, periventricular hemorrhaging and increased perinatal mortality. Notably, Notch ligands accumulate at the cell surface and cleaved NICD is reduced in neural stem cells, consistent with impaired ligand-mediated activation. In contrast, inhibition of CME in receptor-expressing cells increases cell autonomous Notch signaling, likely by promoting receptor accumulation at the plasma membrane. Further, dynamin 1, 2, and 3 can rescue loss of Dnm2 to different extents. Taken together, these findings reveal that Dnm2 is the essential isoform for physiological non-cell autonomous Notch-mediated neural stem cell maintenance, and that CME exerts fundamentally distinct roles in Notch signaling, promoting ligand activity while restricting receptor signaling through control of surface receptor abundance.