Transcription factor AP-2γ is a core regulator of tight junction biogenesis and cavity formation during mouse early embryogenesis

Abstract

The trophectoderm epithelium is the first differentiated cell layer to arise during mammalian development. Blastocyst formation requires the proper expression and localization of tight junction, polarity, ion gradient and H2O channel proteins in the outer cell membranes. However, the underlying transcriptional mechanisms that control their expression are largely unknown. Here, we report that transcription factor AP-2γ (Tcfap2c) is a core regulator of blastocyst formation in mice. Bioinformatics, chromatin immunoprecipitation and transcriptional analysis revealed that Tcfap2c binds and regulates a diverse group of genes expressed during blastocyst formation. RNA interference experiments demonstrated that Tcfap2c regulates genes important for tight junctions, cell polarity and fluid accumulation. Functional and ultrastructural studies revealed that Tcfap2c is necessary for tight junction assembly and paracellular sealing in trophectoderm epithelium. Aggregation of control eight-cell embryos with Tcfap2c knockdown embryos rescued blastocyst formation via direct contribution to the trophectoderm epithelium. Finally, we found that Tcfap2c promotes cellular proliferation via direct repression of p21 transcription during the morula-to-blastocyst transition. We propose a model in which Tcfap2c acts in a hierarchy to facilitate blastocyst formation through transcriptional regulation of core genes involved in tight junction assembly, fluid accumulation and cellular proliferation.

Transcription factor AP-2γ induces early Cdx2 expression and represses HIPPO signaling to specify the trophectoderm lineage

“…We found that TFAP2C is initially widely expressed in the preimplantation embryo, and then, during the morula to blastocyst transition, it becomes enriched in the mural trophectoderm and downregulated in the ICM. Notably, this expression pattern was largely consistent with the role of TFAP2C in tight junction biogenesis and blastocoel formation (Choi et al, 2012), suggesting that TFAP2C is a key trophectoderm-specific transcription factor in the preimplantation embryo. Here we report that TFAP2C plays a much wider regulatory role in early lineage formation.…”

“…We recently established that TFAP2C is a key regulator of genes required for blastocyst formation in mice (Choi et al, 2012). TFAP2C-depleted embryos arrest around the morula stage and fail to establish the trophectoderm epithelium.…”

“…S2). Moreover, the specificity and efficacy of the Tfap2c siRNA sequences were previously tested via an elaborate series of control and rescue experiments (Choi et al, 2012). Cdx2 transcripts were reduced by 77%, 87%, 76% at the 4-cell, 8-cell and morula stage, respectively (Fig.…”

“…Recently, we identified a novel and crucial role for transcription factor AP-2γ (TFAP2C) in the regulation of core processes that underlie blastocyst formation (Choi et al, 2012). We found that TFAP2C is initially widely expressed in the preimplantation embryo, and then, during the morula to blastocyst transition, it becomes enriched in the mural trophectoderm and downregulated in the ICM.…”

Regulation of epithelial cell polarity by PAR-3 depends on Girdin transcription and Girdin–Gαi3 signaling

“…These results suggest that the proximal putative AP-2-binding site is the cis-acting element essential for Girdin transcription. AP-2 is a developmentally regulated transcription factor family that is crucial for the expression of genes such as tight junction regulators during vertebrate development (Choi et al, 2012;Eckert et al, 2005). To evaluate the involvement of AP-2 in Girdin transcription, we next co-transfected the Girdin promoter −891/+41 construct and an AP-2α expression vector into HepG2 cells, which express a low level of endogenous AP-2α and are therefore suitable for AP-2 overexpression studies (Braganca et al, 2003).…”