Y-box protein-1 controls transforming growth factor-beta1 translation in proximal tubular cells

Transforming growth factor-1 (TGF-1) mRNA has low basal translational efficiency in proximal tubule cells; however, its translation is stimulated by profibrotic cytokines. We studied the role of the multifunctional Y-box protein-1 (YB-1) in regulating proximal tubule cell TGF-1 translation. Using RNA-electrophoretic mobility shift assays and ultraviolet crosslinking, we found two protein complexes of 50 and 100 kDa, which bound to the TGF-1 mRNA 5'-untranslated region. Supershift studies using antibodies to YB-1 showed that both sites contained YB-1 as did studies with recombinant YB-1, which demonstrated that it was sufficient to form both complexes. RNA competition experiments confirmed YB-1 binding to the two predicted binding sites; one with high affinity and the other with lower affinity. Strong basal YB-1 association with TGF-1 mRNA was found in proximal tubule cells, which decreased when platelet-derived growth factor was used to activate TGF-1 translation. In contrast, knockdown of proximal tubule cell YB-1 expression abrogated TGF-1 synthesis. Our results suggest that TGF-1 translation in proximal tubule cells requires YB-1 binding to a high-affinity site in the 5'-untranslated region of its mRNA; however, binding to a low-affinity site inhibits basal translation

Adult human kidney organoids originate from CD24(+) cells and represent an advanced model for adult polycystic kidney disease

Adult kidney organoids have been described as strictly tubular epithelia and termed tubuloids. While the cellular origin of tubuloids has remained elusive, here we report that they originate from a distinct CD24(+) epithelial subpopulation. Long-term-cultured CD24(+) cell-derived tubuloids represent a functional human kidney tubule. We show that kidney tubuloids can be used to model the most common inherited kidney disease, namely autosomal dominant polycystic kidney disease (ADPKD), reconstituting the phenotypic hallmark of this disease with cyst formation. Single-cell RNA sequencing of CRISPR-Cas9 gene-edited PKD1- and PKD2-knockout tubuloids and human ADPKD and control tissue shows similarities in upregulation of disease-driving genes. Furthermore, in a proof of concept, we demonstrate that tolvaptan, the only approved drug for ADPKD, has a significant effect on cyst size in tubuloids but no effect on a pluripotent stem cell-derived model. Thus, tubuloids are derived from a tubular epithelial subpopulation and represent an advanced system for ADPKD disease modeling