HNF1B Alters an Evolutionarily Conserved Nephrogenic Program of Target Genes

Area of Science:

• Developmental Biology
• Genetics
• Molecular Biology

Background:

• Mutations in hepatocyte nuclear factor-1 β (HNF1B) are the leading monogenic cause of congenital cystic dysplastic renal malformations.
• The precise functional impact of HNF1B mutations on its transcriptional activity remains largely unknown.

Purpose of the Study:

• To investigate the functional consequences of HNF1B mutations on transcriptional activity using direct reprogramming and Xenopus organoid models.
• To identify conserved transcriptional targets of HNF1B and understand how patient-specific mutations affect gene regulation in nephrogenesis.

Main Methods:

• Direct reprogramming of mouse fibroblasts into induced renal tubular epithelial cells (iRECs) using wild-type and mutant HNF1B.
• Expression of HNF1B in Xenopus ectodermal explants to assess inductive capacity.
• Transcriptomic analysis (RNA-Seq) and CRISPR/Cas9 genome editing in Xenopus embryos to identify and validate HNF1B targets in vivo.

Main Results:

• HNF1B is essential for iREC reprogramming and induces ectopic renal organoids in Xenopus.
• The R295C HNF1B mutation retains inductive capacity but alters the expression of specific downstream genes, rather than reducing overall activity.
• Cross-species conserved targets of HNF1B were identified, with dysregulation observed in HNF1B-depleted Xenopus embryos, confirming functional dependence.

Conclusions:

• HNF1B orchestrates an evolutionarily conserved gene program critical for nephrogenesis.
• Disease-causing HNF1B mutations selectively disrupt this program, providing insights into the genetic circuitry underlying congenital renal anomalies.