The Extracellular Domain of Notch2 Increases Its Cell-Surface Abundance and Ligand Responsiveness during Kidney Development

Notch2, but not Notch1, plays indispensable roles in kidney organogenesis, and Notch2 haploinsufficiency is associated with Alagille syndrome. We proposed that proximal nephron fates are regulated by a threshold that requires nearly all available free Notch intracellular domains (NICDs) but could not identify the mechanism that explains why Notch2 (N2) is more important than Notch1 (N1). By generating mice that swap their ICDs, we establish that the overall protein concentration, expression domain, or ICD amino acid composition does not account for the differential requirement of these receptors. Instead, we find that the N2 extracellular domain (NECD) increases Notch protein localization to the cell surface during kidney development and is cleaved more efficiently upon ligand binding. This context-specific asymmetry in NICD release efficiency is further enhanced by Fringe. Our results indicate that an elevated N1 surface level could compensate for the loss of N2 signal in specific cell contexts. •Notch2 dominance in the kidney is not determined by expression pattern or level•Knockin mice show that Notch1/2 intracellular domains are interchangeable•Notch2 extracellular domain controls cell-surface presentation and ligand response•Tubules and podocytes display greater sensitivity to the dose of Jag1 over Dll1 To test what elements within vertebrate Notch paralogs evolved to endow them with distinct roles, Liu et al. created knockin mice with swapped intracellular domains between Notch1 and Notch2. They found that the extracellular domain contains information that renders Notch2 indispensable during nephrogenesis by increasing surface level and ligand responsiveness.