Transcription factor HNF1β and novel partners affect nephrogenesis

Heterozygous mutations of the tissue-specific transcription factor hepatocyte nuclear factor (HNF)1β, cause maturity onset diabetes of the young (MODY5) and kidney anomalies including agenesis, hypoplasia, dysplasia and cysts. Because of these renal anomalies, HNF1β is classified as a CAKUT (congenital anomalies of the kidney and urinary tract) gene. We searched for human fetal kidney proteins interacting with the N-terminal region of HNF1β using a bacterial two-hybrid system and identified five novel proteins along with the known partner DCoH. The interactions were confirmed for four of these proteins by GST pull-down assays. Overexpression of two proteins, E4F1 and ZFP36L1, in Xenopus embryos interfered with pronephros formation. Further, in situ hybridization showed overlapping expression of HNF1β, E4F1 and ZFP36L1 in the developing pronephros. HNF1β is present largely in the nucleus where it colocalized with E4F1. However, ZFP36L1 was located predominantly in the cytoplasm. A nuclear function for ZFP36L1 was shown as it was able to reduce HNF1β transactivation in a luciferase reporter system. Our studies show novel proteins may cooperate with HNF1β in human metanephric development and propose that E4F1 and ZFP36L1 are CAKUT genes. We searched for mutations in the open reading frame of the ZFP36L1 gene in 58 patients with renal anomalies but found none.