Spalt Like Transcription Factor 3 (Sall3) Is Essential for Maintaining Distal Convoluted Tubule Differentiation

Activation of the sodium chloride cotransporter (NCC, Slc12a3) in the distal convoluted tubule (DCT) by the WNK-SPAK signaling pathway is paralleled by an adaptive remodeling process, characterized by DCT cell proliferation and hypertrophy. Regulatory networks downstream of WNK-SPAK-NCC activation responsible for remodeling and maintaining DCT cell fate have not been identified. Here we determine the role of a DCT-specific transcription factor (TF), Sall3, that is rapidly induced by SPAK-dependent signaling by characterizing the consequences of conditionally and specifically knocking Sall3 out in the DCT. The role of Sall3 in the DCT was characterized in three different mouse models. Specifically, Sall3 was assessed in mice carrying an inducible constitutively active SPAK mutant (CA-SPAK) in the DCT and in wild-type mice after the WNK-SPAK pathway was activated by dietary low potassium stress. An inducible DCT-specific Sall3 gene knockout mouse model was generated, and the phenotype of the mice was characterized using genomic, molecular and quantitative imaging analysis. Differential gene expression analysis in bulk RNA-Seq in mouse kidneys of CA-SPAK mice followed by cell type deconvolution identified Sall3 as a key TF that were significantly induced by chronic SPAK-NCC activation in the DCT. Immunofluorescence microscopy confirmed that SALL3 protein was localized to the DCT nucleus, where it increased in the CA-SPAK mice, and after WNK-SPAK was activated by low potassium stress. Induction of DCT-specific Sall3 KO eliminated SALL3 expression in the nuclei of DCT cells and remarkably reduced expression of NCC and other DCT-specific genes. Quantitative imaging revealed a major collapse of DCT structure, visualized by a 62.1% decrease in NCC+ cells, accompanied by an 50% increase in the number of calbindin positive connecting tubule cells. In summary, Sall3 is a key component of the core transcriptional regulatory circuit that is responsible for maintaining DCT cell identity as the DCT expands in response to chronic NCC activation. When Sall3 is deleted, DCT atrophy is accompanied by an adaptive remodeling of the connecting tubule. NIDDK, Le Ducq Foundation This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.