Kidney Week

Abstract: TH-OR85

Implication of Heterozygous Variants in PROX1 in Congenital Anomalies of the Kidneys and Urinary Tract

Session Information

• Non-Cystic Genetic Kidney Diseases: Disease Genes, Modifiers, and Therapies
  October 24, 2024 | Location: Room 23, Convention Center
  Abstract Time: 05:00 PM - 05:10 PM

Category: Genetic Diseases of the Kidneys

• 1202 Genetic Diseases of the Kidneys: Non-Cystic

Authors

• Kolvenbach, Caroline Maria, Boston Children's Hospital, Boston, Massachusetts, United States

Caroline Maria Kolvenbach, MD, DrMed

• Merz, Lea Maria, Boston Children's Hospital, Boston, Massachusetts, United States

Lea Maria Merz, DrMed, ScM

• Aslam, Faiza, Yale University School of Medicine, New Haven, Connecticut, United States

Faiza Aslam, PhD

• Sanna-Cherchi, Simone, Columbia University Vagelos College of Physicians and Surgeons, New York, New York, United States

Simone Sanna-Cherchi, MD

• Milo Rasouly, Hila, Columbia University Vagelos College of Physicians and Surgeons, New York, New York, United States

Hila Milo Rasouly, MS, MSc, PhD

• Gharavi, Ali G., Columbia University Vagelos College of Physicians and Surgeons, New York, New York, United States

Ali G. Gharavi, MD

• Pena, Sergio D.j., Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil

Sergio D.j. Pena

• Tasic, Velibor, Saints Cyril and Methodius University in Skopje Medical Faculty, Skopje, Skopje, Macedonia (the former Yugoslav Republic of)

Velibor Tasic

• Li, Zhongwei, University of Southern California Keck School of Medicine, Los Angeles, California, United States

Zhongwei Li, PhD

• Shril, Shirlee, Boston Children's Hospital, Boston, Massachusetts, United States

Shirlee Shril

• Hildebrandt, Friedhelm, Boston Children's Hospital, Boston, Massachusetts, United States

Friedhelm Hildebrandt, MD

Background

Congenital anomalies of the kidney and urinary tract (CAKUT) constitute one of the most frequent birth defects and represent the most common cause of chronic kidney disease in the first three decades of life. Despite the discovery of numerous monogenic disease genes, the identification of an underlying molecular diagnosis often remains challenging.

Methods

We applied exome sequencing (ES) to our cohort of 229 CAKUT trios. Subsequent functional analysis of the identified candidate gene PROX1 was performed in vitro and in vivo, employing subcellular localization analyses, luciferase reporter assays, nephron organoid studies and morpholino knockdown experiments in Xenopus larvae.

Results

Through ES and collaboration, we identified 6 individuals with CAKUT and heterozygous variants in PROX1, 2 of them occurring de novo. Of note, one individual additionally presented with lymphedema. This phenotype has been previously associated with heterozygous variants in PROX1 and thus connects the CAKUT phenotype together with the lymphedema manifestations to PROX1. In subcellular localization studies, 1/6 mutants exhibited an aberrant nuclear signal compared to the wild type, which potentially interferes with DNA-interaction of the transcription factor. Luciferase reporter assays demonstrated impaired Wnt (4/6 mutants) and retinoic acid (RA; 5/6 mutants) pathway signaling. In addition, PROX1 partially colocalized with NRIP1, a known CAKUT disease gene. NRIP1 is a key regulator of RA signaling, which we could show was influenced by coexpressing PROX1. RNA-sequencing data of nephron progenitor cells showed expression of PROX1 at this early stage during nephron development, which persisted through the differentiation process to kidney organoids. Moreover, human disease features are replicated in knockdown Xenopus larvae, exhibiting abnormal tubular structure.

Conclusion

Our data indicate that PROX1 variants cause CAKUT by interference with Wnt and RA transcriptional signaling, two major pathways of nephrogenesis.