The TFEB-TGIF1 axis regulates EMT in mouse epicardial cells

Abstract

Epithelial-mesenchymal transition (EMT) is a complex and pivotal process involved in organogenesis and is related to several pathological processes, including cancer and fibrosis. During heart development, EMT mediates the conversion of epicardial cells into vascular smooth muscle cells and cardiac interstitial fibroblasts. Here, we show that the oncogenic transcription factor EB (TFEB) is a key regulator of EMT in epicardial cells and that its genetic overexpression in mouse epicardium is lethal due to heart defects linked to impaired EMT. TFEB specifically orchestrates the EMT-promoting function of transforming growth factor (TGF) β, and this effect results from activated transcription of thymine-guanine-interacting factor (TGIF)1, a TGFβ/Smad pathway repressor. The Tgif1 promoter is activated by TFEB, and in vitro and in vivo findings demonstrate its increased expression when Tfeb is overexpressed. Furthermore, Tfeb overexpression in vitro prevents TGFβ-induced EMT, and this effect is abolished by Tgif1 silencing. Tfeb loss of function, similar to that of Tgif1, sensitizes cells to TGFβ, inducing an EMT response to low doses of TGFβ. Together, our findings reveal an unexpected function of TFEB in regulating EMT, which might provide insights into injured heart repair and control of cancer progression.

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“…Interestingly, a bioinformatics analysis based on the chromatin immunoprecipitation (ChIP) sequencing (seq) binding dataset obtained from a murine model [ 59 ] highlighted the enrichment of TFEB at the Dusp-1 promoter region (Supplementary Fig. S2C ), which was defined as the sequence (−2500; +2500, mouse mm9 genome) extending from the transcription start site (TSS) of the Dusp1 transcript variant ENSMUST00000025025.…”

“…1C ) assay. Chip analysis performed in scr-shRNA or in sh-TFEB D4M cells after the addition of WT TFEB (WT-TFEB), the constitutively active nuclear TFEB mutant (TFEBS142A) or the inactive cytosolic TFEB mutant (TFEB ΔNLS) [ 59 , 61 , 62 ] confirmed TFEB binding to the Dusp-1 promoter (Supplementary Fig. S2D and Fig.…”

“…We further investigated Dusp-1 promoter activity by luciferase reporter assay in D4M cells carrying luciferase reporter vectors harbouring: (i) the full-length Dusp-1 promoter; (ii) a promoter lacking the putative TFEB-binding site (Del1) located in a region extending from −328 and +333 bp with respect to the TSS of the selected Dusp-1 transcript, as determined by ChIP-seq analysis [ 59 ]; (iii) a promoter lacking the putative TFEB-binding site and a sequence of 100 bp before and after this binding site (Del2) (Supplementary Fig. S3A ).…”

“…S3C ). The analysis of the ChIP-seq binding dataset [ 59 ] did not show enrichment of TFEB at the Ccnd1 promoter region (Supplementary Fig. S3D ) but suggested direct binding to the Cdk4 promoter (Fig.…”

“…Performing luciferase reporter assays, we further investigated Cdk4 promoter activity in D4M cells carrying luciferase reporter vectors harbouring: (i) the full-length Cdk4 promoter; (ii) a promoter lacking the putative TFEB-binding site (Del1), as determined by ChIP-seq analysis, −376 and +278 bps from TSS of selected Cdk4 transcript [ 59 ]; (iii) a promoter lacking the putative TFEB-binding site and a sequence of 100 bp before and after the same binding site (Del2) (Supplementary Fig. S3A ).…”