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If an escalator stops working, passive passengers will accumulate both on the stairs and in a disgruntled cluster at the start. This is what happens if the ureter connecting kidney and bladder cannot effectively move urine through the system. The backlog in both ureter and kidney is characteristic of Mowat-Wilson syndrome, a rare genetic disorder caused by mutations in the ZEB2 gene that causes a wide range of developmental defects. To understand what role ZEB2 plays in ureter development, researchers studied genetically engineered mice in which the gene was deleted in ureter precursor cells. In these mice, cells that normally become smooth muscle cells (red in the mouse ureter section, left) fail to develop (right). Without this muscle layer, the ureter can’t contract to move urine, causing swelling of the ureter and kidney and ultimately obstruction, revealing a key molecular mechanism underlying urinary tract anomalies in Mowat-Wilson syndrome patients.

Written by Anthony Lewis

Anthony Lewis

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Ant was the web editor in the early days of BPoD, and has since worked with the UK’s top science organisations as a writer and multimedia producer. He now splits his time between freelance work and managing multimedia at The Lancet.

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• Image from work by Sudhir Kumar and colleagues
• Nephrology Section, Department of Medicine, Boston University Chobanian & Avedisian School of Medicine, Boston Medical Center, Boston, MA, USA
• Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)
• Published in PLOS Genetics, January 2026