Dmrt2 and Hmx2 direct intercalated cell diversity in the mammalian kidney through antagonistic and supporting regulatory processes.

Intercalated cells (ICs) in the mammalian kidney regulate circulatory pH through IC subtype-restricted actions of bicarbonate transporters: pH is elevated by Slc4a1 restricted to type A-ICs (A-ICs) and depressed by Slc26a4 in type B-IC (B-ICs). NonA-nonB-ICs (nA/nB-ICs) also produce Slc26a4 though their function is unclear. Though both nephron and ureteric progenitor lineages generate A-ICs, the former also generates nA/nB-ICs and the latter B-ICs. Lineage and cell type restricted transporter gene expression in the mouse and human kidney is preceded by expression of the transcriptional regulators in A-ICs, and either, or both, and in B- and nA/nB ICs. CRISPR/Cas9-directed removal of and the linked / resulted in IC-subtype switching. A-ICs adopted an B-IC cell fate on Dmrt2 removal while B-ICs initiated a Dmrt2/Slc4a1 A-IC program on removal. Triple knockout of , , and resulted in hybrid ICs expressing both and . Thus, restricted expression of these regulators is essential for specifying IC subtypes. To explore these mechanisms, and were activated ectopically in ureteric organoid cultures. Introduction of -a pan determinant of ICs-activated early A-IC development while cointroduction of silenced Foxi1-dependent expression and led to an upregulation of Slc26a4. In contrast, coexpression of and upregulated . These data support a model in which mutually repressive interactions between and establish distinct IC identities and ongoing activity of these factors supports gene regulatory programs specific to each IC subtype.