Adhesion, but not a specific cadherin code, is indispensable for ES cell and induced pluripotency

Abstract

Embryonic stem (ES) cell pluripotency and induced pluripotent stem (iPS) cell generation is dependent on a core transcriptional network and proper cell-cell adhesion mediated by E-cadherin (E-cad). Whereas E-cad is associated with pluripotency, N-cadherin (N-cad) expression is correlated with differentiation into mesodermal and neuroectodermal lineages. We investigated whether E-cad harbors unique molecular features in establishing or maintaining pluripotency. By using a gene replacement knock-in (ki) approach to express N-cadherin (N-cad) or E-cad/N-cad chimeric cadherins under the control of the E-cad locus, we show that all E-cad-depleted ki/ki ES cells are maintained in an undifferentiated state. Surprisingly, these cells retained key features of pluripotency, such as Nanog expression and full differentiation capacity in vitro and in vivo, whereas E-cad knockout (ko) ES cells irreversibly lost most of these features. Moreover, our results indicate that E-cad mediated adhesion is essential for iPS cell generation, since E-cad depleted fibroblasts were not reprogrammed. In contrast, N-cad efficiently supports somatic reprogramming similar to E-cad, and permits initiation of the crucial initial step of mesenchymal-epithelial transition. Thus, we show that cell adhesion and a robust pluripotent phenotype are ultimately connected. Since N-cad properly compensates for loss of E-cad, no specific 'cadherin code' is required.

Role of cell–cell adhesion complexes in embryonic stem cell biology

“…This partial restoration is sensitive to both a JAK inhibitor and an E-and N-cadherin-inhibiting peptide (Hawkins et al, 2012). In line with this, knock-in of either wild-type N-cadherin or adhesioncompetent chimeric forms of E-and N-cadherin into the Cdh1 locus does not interfere with embryonic derivation or pluripotency of naive mESCs (Bedzhov et al, 2013).…”

“…In many instances, blocking the inverse process epithelial-tomesenchymal transition (EMT) appears to be an efficient way for reprogramming of various somatic cell types (Fig. 3B), although recent findings indicate that reprogramming is more complex than previously anticipated (discussed below) (Bedzhov et al, 2013;Liu et al, 2013). During EMT, epithelial cells undergo transcriptional changes, altered adhesion and cytoskeletal rearrangements and, eventually, acquire a mesenchymal phenotype.…”

“…These findings were corroborated by the highly limited contribution of Cdh1 2/2 mESCs to chimeric embryos (Larue et al, 1996). The forced expression of E-cadherin in Cdh1 2/2 mESCs considerably increases the degree of chimerism, whereas mESCs with forced expression of N-cadherin or with a knock-in of N-cadherin into the Cdh1 locus only modestly contribute to chimeras (Bedzhov et al, 2013;Larue et al, 1996). The poor contribution of Cdh1 2/2 mESCs to chimeras could be explained by an inadequate cellular mixing of loosely attached Cdh1 2/2 mESCs with ICM cells in the recipient blastocysts.…”

“…Likewise, reprogramming was stimulated when cells were treated briefly with TGFb in combination with the original OSKM cocktail, thereby inducing early EMT . Moreover, although endogenous N-cadherin expression is a hallmark of EMT, a MET program leading to fibroblast reprogramming can also be driven by N-cadherin that is ectopically expressed from a knock-in cDNA at the Cdh1 locus (Bedzhov et al, 2013). This indicates that not so much the type of classic cadherin is important for somatic cell reprogramming but, instead, the timing and the macromolecular context of cadherin induction and activation.…”

Developmental plasticity, cell fate specification and morphogenesis in the early mouse embryo

“…For example, EBs and embryos differ in their initial cell number. While EBs contain a few hundreds of cells on the first day of culture, the EPI of the implanting blastocyst consists of only 8–16 cells [36,143]. The second difference is timing.…”