# Transcription factor ZEB2 is essential for ureteral smooth muscle cell differentiation

## TL;DR

This study shows that the ZEB2 gene is crucial for developing ureter smooth muscle cells, explaining why some MWS patients have urinary tract issues.

## Contribution

The study reveals ZEB2's role in ureteral smooth muscle cell differentiation and its link to MWS-related urinary tract anomalies.

## Key findings

- Deleting ZEB2 in ureteral mesenchymal cells caused hydroureter and hydronephrosis in mice.
- Loss of ZEB2 led to absence of smooth muscle cells and expansion of tunica adventitia cells in the ureter.
- Molecular analysis showed decreased TBX18 and increased SOX9 in ZEB2-deficient ureters.

## Abstract

Mowat-Wilson Syndrome (MWS) is an autosomal dominant genetic disorder caused by heterozygous mutations or deletions in the Zinc finger E-box-binding homeobox 2 (ZEB2) gene. Congenital anomalies of the kidney and urinary tract (CAKUT), including hydroureter and hydronephrosis, have been reported in patients with MWS. However, the role of the ZEB2 gene in urinary tract development and the cellular and molecular mechanisms underlying the CAKUT phenotypes in MWS remain unknown. In this study, we examined ZEB2 expression in the developing mouse ureter and generated Zeb2 ureteral mesenchyme-specific conditional knockout mice (Zeb2 cKO) by crossing Zeb2 floxed mice with Tbx18Cre+ mice. The urinary tract of Zeb2 cKO mice and their wild-type littermates was analyzed for morphological and histological changes. Our results show that ZEB2 is expressed in TBX18+ ureteral mesenchymal cells during mouse ureter development. Deleting Zeb2 in these cells caused hydroureter and hydronephrosis, indicating obstructive uropathy. Cellular and molecular marker analysis revealed that the TAGLN+ACTA2+ ureteral smooth muscle cell (SMC) layer was absent in Zeb2 cKO mice. In contrast, the tunica adventitia cell layer was significantly expanded compared to controls. At the molecular level, Zeb2 cKO mice had significantly decreased TBX18 expression but increased SOX9 expression in the developing ureter compared to wild-type controls. Our findings demonstrate that ZEB2 is crucial for normal ureteral SMC differentiation during ureter development. Additionally, our study suggests that MWS patients may have abnormal ureteral SMC development, which contributes to the abnormalities of the urinary tract.

Hydroureter and hydronephrosis are common congenital anomalies with a high incidence (1:100–1:500) that can lead to obstructive uropathy and renal failure in the pediatric population. Mowat-Wilson Syndrome (MWS), caused by heterozygous mutations in the ZEB2 gene, is a genetic disorder characterized by multiple congenital developmental defects, including hydroureter and hydronephrosis. However, the molecular function of ZEB2 in ureter development and the pathogenesis of hydroureter and hydronephrosis remain unknown. Here, we demonstrate that ZEB2 is expressed in developing ureteral mesenchymal cells, and the deletion of ZEB2 in these cells leads to the loss of ureteral smooth muscle cells, which are replaced by tunica adventitia cells, resulting in a hydroureter and hydronephrosis phenotype. Hence, our work not only demonstrates the critical role of ZEB2 in ureter development but also provides insight into the molecular mechanisms underlying urinary tract anomalies in MWS patients.