Characterization of splice isoform switching during human kidney development

Background: Nephrons are the functional units of the kidney. During kidney development, cells from the cap mesenchyme – a transient kidney-specific progenitor state – undergo a mesenchymal to epithelial transition (MET) and subsequently differentiate into the various epithelial cell types that create the tubular structures of the nephron. Faults in this transition can lead to a pediatric malignancy of the kidney called Wilms' tumor that mimics normal kidney development. While human kidney development has been characterized at the gene expression level, a comprehensive characterization of alternative splicing is lacking. Methods: We performed RNA sequencing on cell populations representing early, intermediate, and late developmental stages of the human fetal kidney, as well as three blastemal-predominant Wilms' tumor patient-derived xenografts. Results: We identified a set of transcripts that are alternatively spliced between the different developmental stages. Moreover, we found that cells from the earliest developmental stage have a mesenchymal splice-isoform profile that is similar to that of blastemal-predominant Wilms' tumors. RNA binding motif enrichment analysis suggests that the mRNA binding proteins ESRP1, ESRP2, RBFOX2, and QKI regulate mRNA splice isoform switching during human kidney development. Conclusions: These findings illuminate new molecular mechanisms involved in human kidney development and pediatric kidney tumors. Overall design: We performed RNA sequencing on three cell populations representing early, intermediate, and late developmental stages of the human fetal kidney, and on three blastemal-predominant Wilms' tumor patient-derived xenografts.