Epithelial-Mesenchymal Transition Functions as a Driver for the Direct Conversion of Somatic Cells

Direct conversion is an innovative new technology that involves the conversion of somatic cells to target cells without passing through a pluripotent state. Forced expression alone or in combination with transcription factors (TFs), which are critical for the generation of target cells, is important for successful direct conversion. However, most somatic cells are unable to directly convert into target cells even with forced expression. We herein demonstrated that epithelial-mesenchymal transition (EMT) is advantageous for the direct conversion of somatic cells. We previously reported that mouse keratinocytes converted into neural crest cells (NCCs) following the forced expression of the NCC specifier Sox10 in combination with expression of the TFs Snail1, Slug, Twist1, and Tcfap2a (4 TFs). 4 TFs induced EMT in keratinocytes; therefore, EMT was considered to be advantageous for direct conversion. The direct conversion of mouse mammary gland epithelial cells (NMuMG cells) into NCCs was not observed with the forced expression of Sox10, but was detected with the expression of Sox10 following the induction of EMT by 4 TFs. Furthermore, TGF-β1-induced EMT and Sox10 expression directly converted NMuMG cells into NCCs. These results suggest that the induction of EMT in somatic cells is advantageous for direct conversion.