Single-Cell RNA Sequencing Reveals mRNA Splice Isoform Switching during Kidney Development

Significance Statement Kidney development is a complex process involving multiple interacting and transitioning cell types. Drop-seq single-cell technology, which measures gene expression from many thousands of individual cells, has been used to characterize these cellular differentiation changes that underlie organ development. However, the alternative splicing of many genes creates an additional layer of cellular heterogeneity that Drop-seq technology cannot measure. Therefore, in this study, full transcript length single-cell RNA sequencing was used to characterize alternative splicing in the mouse embryonic kidney, with particular attention to the identification of genes that are alternatively spliced during the transition from mesenchymal to epithelial cell states, as well as their splicing regulators. These results improve our understanding of the molecular mechanisms that underlie kidney development. Background During mammalian kidney development, nephron progenitors undergo a mesenchymal-to-epithelial transition and eventually differentiate into the various tubular segments of the nephron. Recently, Drop-seq single-cell RNA sequencing technology for measuring gene expression from thousands of individual cells identified the different cell types in the developing kidney. However, that analysis did not include the additional layer of heterogeneity that alternative mRNA splicing creates. Methods Full transcript length single-cell RNA sequencing characterized the transcriptomes of 544 individual cells from mouse embryonic kidneys. Results Gene expression levels measured with full transcript length single-cell RNA sequencing identified each cell type. Further analysis comprehensively characterized splice isoform switching during the transition between mesenchymal and epithelial cellular states, which is a key transitional process in kidney development. The study also identified several putative splicing regulators, including the genes Esrp1/2 and Rbfox1/2 . Conclusions Discovery of the sets of genes that are alternatively spliced as the fetal kidney mesenchyme differentiates into tubular epithelium will improve our understanding of the molecular mechanisms that drive kidney development.