OVOL2 induces mesenchymal-to-epithelial transition in fibroblasts and enhances cell-state reprogramming towards epithelial lineages

Abstract

Mesenchymal-to-epithelial transition (MET) is an important step in cell reprogramming from fibroblasts (a cell type frequently used for this purpose) to various epithelial cell types. However, the mechanism underlying MET induction in fibroblasts remains to be understood. The present study aimed to identify the transcription factors (TFs) that efficiently induce MET in dermal fibroblasts. OVOL2 was identified as a potent inducer of key epithelial genes, and OVOL2 cooperatively enhanced MET induced by HNF1A, TP63, and KLF4, which are known reprogramming TFs to epithelial lineages. In TP63/KLF4-induced keratinocyte-like cell-state reprogramming, OVOL2 greatly facilitated the activation of epithelial and keratinocyte-specific genes. This was accompanied by enhanced changes in chromatin accessibility across the genome. Mechanistically, motif enrichment analysis revealed that the target loci of KLF4 and TP63 become accessible upon induction of TFs, whereas the OVOL2 target loci become inaccessible. This indicates that KLF4 and TP63 positively regulate keratinocyte-associated genes whereas OVOL2 suppresses fibroblast-associated genes. The exogenous expression of OVOL2 therefore disrupts fibroblast lineage identity and facilitates fibroblast cell reprogramming into epithelial lineages cooperatively with tissue-specific reprogramming factors. Identification of OVOL2 as an MET inducer and an epithelial reprogramming enhancer in fibroblasts provides new insights into cellular reprogramming improvement for future applications.

The Transcription Factor OVOL2 Represses ID2 and Drives Differentiation of Trophoblast Stem Cells and Placental Development in Mice

“…Our findings that OVOL2 suppresses TS cell proliferation are consistent with the known tumor suppressor functions of OVOL2 in other cell types [27]. OVOL2 inhibits cell proliferation and protects epithelial identity by regulating Wnt signaling [14,[28][29][30], repressing oncogenes (e.g., c-Myc) [24], and reducing expression of genes associated with epithelial-to-mesenchymal transition [16,27,[31][32][33][34]. Interestingly, in our study, expression of Eomes, Esrrb, and Id2 remained higher in Ovol2-null TS cells even when cultured in differentiation conditions, resulting in diminished capacity to upregulate differentiation markers including Gcm1, Syna, Prl3b1, and Ascl2.…”

OVOL1/2: Drivers of Epithelial Differentiation in Development, Disease and Reprogramming

“…OVOL1 in combination with some or all of the selected critical regulators of epidermal fate (PRDM1, p63, KLF4, ZNF750, and GRHL3) has been shown to be sufficient for the rapid conversion of human dermal fibroblasts to an induced keratinocyte phenotype (iKP) expressing keratinocyte specific genes: KRT14 and GJB2 [Chen et al, 2014]. Furthermore, OVOL2 has been shown to cooperatively promote MET in fibroblasts to keratinocytes induced by epithelial lineage promoting transcription factors such as HNF1A, TP63, and KLF4 by inducing genes involved in epithelial phenotype and repressing fibroblast-associated genes [Watanabe et al, 2019]. Similarly, reprogramming of human fibroblast cells to corneal epithelial cells (CECs) was done by overexpressing core CEC network consisting of PAX6, OVOL2 and KLF4.…”

“…1) [Mackay et al, 2006;Teng et al, 2007;Nair et al, 2006;Kohn et al, 2014;Sun et al, 2019]. OVOL1/2 can inhibit epithelial-mesenchymal transition (EMT) by directly repressing EMT inducing transcription factors (EMT-TFs) such as ZEB1, ZEB2, TWIST and promote the reverse of EMT -mesenchymal-epithelial transition (MET) by inducing the expression of cell-cell adhesion molecule E-cadherin [Kitazawa et al, 2019;Watanabe et al, 2019;Aue et al, 2015]. Thus, OVOL1/2 can be thought of as one of MET-inducing transcription factors (MET-TFs), similar to GRHL2 [Frisch et al, 2017;Mooney et al, 2017].…”

New Trends in Regenerative Medicine: Reprogramming and Reconditioning

“…5 More recently, an ovo-like Zinc-finger 2 transcription repressor factor has been shown enhance mesenchymal-to-epithelial (keratinocyte) transition. 6 Those approaches for direct cell reprogramming should not conflict with the results of in vivo clonal analysis of mammalian kidney, which revealed fate-restricted unipotent segment-specific progenitors involved in tubulogenesis, maintenance, and regeneration. 7 In vivo administration of mesenchymal stem cells or their conditioned culture medium salvaged kidney function after AKI via a paracrine effect.…”