Hnf4a-mediated regulation of proximal tubule progenitors in the mouse kidney

Background: Hnf4a is a major regulator of renal proximal tubule (PT) development. In humans, a mutation in HNF4A is associated with Fanconi renotubular syndrome (FRTS), which is caused by defective PT functions. In mice, mosaic deletion of Hnf4a in the developing kidney causes a paucity of PT cells, leading to FRTS-like symptoms. The molecular mechanisms underlying the role of Hnf4a in PT development remain unclear. Methods: We generated a new Hnf4a mutant mouse model employing Osr2Cre, which effectively deletes Hnf4a in developing nephrons. We characterized the mutant phenotype by immunofluorescence analysis. We performed lineage analysis to test if Cdh6+ cells are PT progenitors. We also performed genome-wide mapping of Hnf4a binding sites and differential gene analysis of Hnf4a mutant kidneys to identify direct target genes of Hnf4a. Results: Deletion of Hnf4a with Osr2Cre led to complete loss of mature PT cells, causing lethality in the Hnf4a mutant mice. We found that Cdh6high, LTLlow cells serve as PT progenitors and that they show higher proliferation than Cdh6low, LTLhigh differentiated PT cells. We also found that Hnf4a is required for PT progenitors to develop into differentiated PT cells. Our genomic analyses revealed that Hnf4a directly regulates the expression of genes involved in transmembrane transport and metabolism. Conclusion: Our findings show that Hnf4a promotes the development of PT progenitors into differentiated PT cells by regulating the expression of genes associated with reabsorption, the major function of PT cells.