Kidney organoids: A system to study human basement membrane assembly in health and disease

Basement membranes (BMs) are complex macromolecular networks that underlie continuous layers of cells. Essential components include type IV collagen and laminins, which are affected by human genetic defects leading to kidney, muscle, and cerebrovascular phenotypes. We investigated the dynamics of BM assembly in human pluripotent stem cell derived kidney organoids. Across organoid differentiation and in parallel with analyses of fetal kidneys we resolved global BM composition and discovered a conserved temporal sequence in BM assembly. We identified key BM isoform emergence, which was altered by a pathogenic variant in COL4A5. Integrating organoid, fetal and adult kidney proteomes we found dynamic regulation of BM composition through development to adulthood, and with single-cell transcriptomic analysis we identified cellular origins of key BM components. Overall, we define the complex and dynamic nature of vertebrate BM assembly and provide a platform for understanding the wider relevance in human development and disease.