Loss of transcription factor ATOH8 activates TGF-β signaling and exacerbates glomerulosclerosis in podocytes

Atonal BHLH transcription factor 8 (<i>ATOH8</i>) is a basic helix-loop-helix (bHLH) transcription factor; however, its role in glomerular epithelial cells (podocytes) remains unclear. This study aimed to elucidate the function of ATOH8 in podocytes. First, ATOH8 expression in the mouse kidney was confirmed in podocytes by immunofluorescence staining and in situ hybridization. In cultured human podocytes, transforming growth factor-beta (TGF-β) treatment significantly reduced <i>ATOH8</i> mRNA expression. To examine the functional consequences of ATOH8 downregulation, <i>ATOH8</i> expression was knocked down with shRNA. Subsequent RNA sequencing analysis of <i>ATOH8</i>-knockdown podocytes revealed increased extracellular matrix gene expression and activation of TGF-β signaling. <i>ATOH8</i>-knockdown podocytes also showed SMAD2/3 nuclear translocation, increased SMAD transcriptional activity, as determined by a luciferase assay, and upregulated <i>TGFB1</i> mRNA even without TGF-β stimulation, consistent with TGF-β signaling activation. In vivo, C57BL/6 <i>Atoh8</i>-deficient mice showed no renal abnormalities at baseline. However, in an adriamycin (ADR)-induced focal segmental glomerulosclerosis (FSGS) model, <i>Atoh8</i>-deficient mice developed significantly more severe glomerulosclerosis than wild-type mice, with higher renal cortical <i>Tgfb1</i> and <i>Col4a1</i> mRNA levels. Reduced ATOH8 expression was also observed in ADR-induced nephropathy in mice and rats and in various human glomerular diseases. These findings suggest that ATOH8 downregulation enhances TGF-β signaling and glomerulosclerosis progression, indicating a protective role for ATOH8 in maintaining podocyte integrity and preventing kidney injury.<b>NEW & NOTEWORTHY</b> This study identifies atonal transcription factor 8 (ATOH8) as a previously unexplored regulator of podocyte function. We demonstrate that ATOH8 knockdown activates TGF-β signaling and increases extracellular matrix gene expression. Notably, ATOH8 deficiency alone does not cause renal injury but exacerbates glomerulosclerosis in an adriamycin-induced nephropathy model, accompanied by increased <i>Tgfb1</i> mRNA expression in the renal cortex. These findings indicate that ATOH8 plays a protective role in podocyte function and limits glomerulosclerosis during kidney injury.