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Kidney Week

Abstract: TH-PO708

Mutations in BNC2 Lead to Autosomal-Dominant Lower Urinary Tract Obstruction (LUTO)

Session Information

Category: Genetic Diseases of the Kidney

  • 1002 Genetic Diseases of the Kidney: Non-Cystic

Authors

  • Kolvenbach, Caroline M., Harvard Medical School, Boston, United States
  • Dworschak, Gabriel C., Boston Children's Hospital, Boston, Massachusetts, United States
  • Frese, Sandra, Universität Bonn, Bonn, Germany
  • Japp, Anna Sophia, University Bonn Medical Center, Bonn, Germany
  • Schmidt, Johanna Magdalena M., Faculty of Medicine, University of Bonn, Bonn, Germany
  • Zaniew, Marcin, Children''s Hospital, Pozna?, Poland
  • Newman, William G., University of Manchester, Manchester, Manchester, United Kingdom
  • Beaman, Glenda Maria, University of Manchester, Manchester, Manchester, United Kingdom
  • Stuart, Helen M., University of Manchester, Manchester, Manchester, United Kingdom
  • Woolf, Adrian S., University of Manchester, Manchester, Manchester, United Kingdom
  • Cervellione, Raimondo Maximilian, Royal Manchester Children''s Hospital, Manchester, United Kingdom
  • Rösch, Wolfgang H., University Medical Center Regensburg, Regensburg, Germany
  • Weber, Stefanie, University Children's Hospital Marburg, Marburg, Germany
  • Hildebrandt, Friedhelm, Boston Children's Hospital, Boston, Massachusetts, United States
  • Hoppe, Bernd, University Hospital Bonn, Bonn, Germany
  • Altmüller, Janine, Cologne Center for Genomics, Cologne, Germany
  • Berg, Christoph, University of Cologne, Cologne, Germany
  • Reutter, Heiko M., University of Bonn, Bonn, Germany
  • Odermatt, Benjamin, University of Bonn, Bonn, Germany
  • Hilger, Alina, University Hospital Bonn, Bonn, Germany
Background

Congenital “lower urinary tract obstruction” (LUTO) is defined by a decrease in the free passage of urine through the urethra. About three out of 10,000 pregnancies are affected; the etiology is so far unknown.

Methods

Whole exome sequencing (WES) in a family with 4 affected from 3 generations was performed. 258 LUTO patients were screened for further variants in the identified candidate gene BNC2 using Sanger sequencing. Functional studies comprised in situ hybridization (ISH) studies in mouse embryos, translational knock-down (KD) in developing zebrafish larvae (zfl) using Morpholino oligonucleotides (MO) and 'rescue‘ experiments by co-injection of human BNC2 mRNA with the bnc2-MO in zfl as well as overexpression of BNC2 mRNA in zfl.

Results

Filtering of WES Data revealed a nonsense mutation (c.2554C>T; p.Arg852*) in BNC2 (basonuclin 2). Out of 258 LUTO patients one additional family (affected father and son) carrying a novel missense mutation (c.2663A>G, p.H888R) in BNC2 could be identified. Affected members in both families presented with anatomical obstruction of the urethra due to posterior urethral valves (PUV), requiring surgical removal, and urethral stenosis with fetal presentation, requiring surgical reconstruction. Functional characterization of Bnc2 using ISH showed expression at E13.5 in developing mouse urethra. KD of bnc2 by injection MO in zfl caused cloacal obstruction with formation of a vesicle at the distal end of pronephric duct in 11% of zfl and cystic dilated deformed glomeruli and dilated pronephric ducts in 50%. Co-injection of human BNC2 mRNA with bnc2-MO in zfl showed rescue of the phenotype only at an amount of 100pg of mRNA. Already slight overexpression of human BNC2 mRNA in zfl lead to the same phenotype as KD, confirming the specificity of the bnc2-MO suggesting that the observed phenotypes in fish and human are the result of gene dosage imbalance of BNC2.

Conclusion

Human genetic and developmental biology models suggest BNC2 mutations as the first monogenic cause of LUTO.