Arid1a regulates bladder urothelium formation and maintenance

Epigenetic regulation of gene expression plays a central role in bladder urothelium development and mainte-nance. ATPase-dependent chromatin remodeling is a major epigenetic regulatory mechanism, but its role in the bladder has not been explored. Here, we show the functions of Arid1a, the largest subunit of the SWI/SNF or BAF chromatin remodeling ATPase complex, in embryonic and adult bladder urothelium. Knockout of Arid1a in urothelial progenitor cells significantly increases cell proliferation during bladder development. Deletion of Arid1a causes ectopic cell proliferation in the terminally differentiated superficial cells in adult mice. Consistently, gene-set enrichment analysis of differentially expressed genes demonstrates that the cell cycle-related pathways are significantly enriched in Arid1a knockouts. Gene-set of the polycomb repression complex 2 (PRC2) pathway is also enriched, suggesting that Arid1a antagonizes the PRC2-dependent epigenetic gene silencing program in the bladder. During acute cyclophosphamide-induced bladder injury, Arid1a knockouts develop hyperproliferative and hyperinfiammatory phenotypes and exhibit a severe loss of urothelial cells. A Hallmark gene-set of the oxidative phosphorylation pathway is significantly reduced in Aria1a mutants before injury and is unexpectedly enriched during injury response. Together, this study uncovers functions of Arid1a in both bladder progenitor cells and the mature urothelium, suggesting its critical roles in urothelial development and regeneration.

Automated summary

Epigenetic regulation, specifically through the ATPase-dependent chromatin remodeling mechanism, plays a central role in bladder urothelium development and maintenance. This study uncovers the functions of Arid1a, a subunit of the SWI/SNF or BAF chromatin remodeling ATPase complex, in both embryonic and adult bladder urothelium. Arid1a deletion leads to increased cell proliferation and ectopic cell proliferation in the bladder, and also antagonizes the PRC2-dependent epigenetic gene silencing program. These findings highlight the critical roles of Arid1a in urothelial development and regeneration.