Sall3: A Potential Master Regulator of Distal Convoluted Tubule Cell Identity via Epigenetic Modeling

The distal convoluted tubule (DCT) is a highly plastic nephron segment as prolonged activation of the WNK-SPAK-NCC signaling pathway induces adaptive structural remodeling, resulting in DCT cell hypertrophy and hyperplasia, paralleled by atrophy of the adjacent connecting tubule (CNT). In a mouse model of chronic NCC activation, the constitutively active SPAK mouse, bulk kidney RNA-Seq and cell type deconvolution identified Spalt like factor 3 (Sall3) as a key DCT specific transcription factor that is significantly upregulated in response to SPAK-NCC activation. DCT-specific Sall3 knockout mice show loss of nuclear Sall3 expression in DCT cells, reduced expression of NCC and other DCT markers, and a concomitant reduction in DCT cells and an increase in CNT cells, indicative of DCT atrophy or transdifferentiation. These findings indicate that Sall3 is required to maintain DCT differentiation. Prior studies also suggest that Sall3 may influence epigenetic states, as its interaction with the DNA methyltransferase DNMT3A can reduce de novo CpG island methylation. Here, we test the role of Sall3 in maintaining DCT cell identity by regulating methylation (gene expression) of DCT-specific genes’ CpG islands via its interaction with Dnmt3a. Immunofluorescence staining revealed nuclear colocalization of Sall3 and Dnmt3a in mouse kidney DCT and HEK cells co-transfected with Sall3 and Dnmt3a. Co-immunoprecipitation analyses further validated this protein-protein interaction. Coexpression also resulted in increased Sall3 protein abundance, suggesting that DNMT3a may stabilize Sall3. RT-qPCR analysis of mouse kidneys revealed DCT-specific Sall3 KO reduces the expression of DCT-specific genes with CpG island-containing promoters that are predicted to be under the control of Sall3-Dnmt3a. An in vitro assay has been developed to test if Sall3-Dnmt3a is sufficient to control CpG island methylation of DCT-specific genes. These results support a model in which Sall3’s interaction with DNMT3a shapes the epigenetic fingerprint of DCT cells, thereby sustaining the expression of DCT-specific genes and maintaining DCT fate. This abstract was presented at the American Physiology Summit 2026 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.