Kruppel-like factor 5 is Required for Urothelial Maturation

Kruppel-like transcription factor 5 (Klf5) is expressed during late embryogenesis in the forming murine bladder urothelium. Targeted disruption of the Klf5flox alleles by the ShhGfpCre transgene resulted in failure of the bladder urothelium to mature accompanied by hydronephrosis, hydroureter, and vesicoureteric reflux in all E18.5 fetuses. The bladder urothelium did not stratify nor did it express terminal differentiation markers characteristic of basal, intermediate, and umbrella cells including keratins 20, 14, and 5, and uroplakins. At E18.5, an ectopic alpha smooth muscle actin positive layer of cells was identified subjacent to the undifferentiated Klf5-deficient urothelium. The effects of Klf5 deficiency were unique to the urothelium since maturation of the epithelium comprising the bladder neck and urethra were unaffected by the lack of KLF5. mRNA microarray analysis of whole E14.5 control and Klf5 deficient bladders identified Ppar-gamma and Grhl3 as putative downstream intermediary transcription factors that regulate urothelial maturation. Transient transfection assays demonstrated that KLF5 regulated expression of the mGrhl3 promoter. These observations show that alterations in maturation of the bladder urothelium alone are sufficient to induce bladder dysfunction leading to prenatal hydronephrosis. Total RNA from E14.5 whole bladders isolated from Klf5D/D and Klf5+/+ShhGfpCre+ embryos (n=3 samples/genotype, each sample a pool of two bladders) was isolated using the Qiagen MicroRNA Kit. The cDNA was then hybridized according to the manufacturer’s protocol to the Affymetrix Mouse Gene 1.0 ST Array