TEAD4 establishes the energy homeostasis essential for blastocoel formation

Abstract

SUMMARYIt has been suggested that during mouse preimplantation development, the zygotically expressed transcription factor TEAD4 is essential for specification of the trophectoderm lineage required for producing a blastocyst. Here we show that blastocysts can form without TEAD4 but that TEAD4 is required to prevent oxidative stress when blastocoel formation is accompanied by increased oxidative phosphorylation that leads to the production of reactive oxygen species (ROS). Both two-cell and eight-cell Tead4 -/− embryos developed into blastocysts when cultured under conditions that alleviate oxidative stress, and Tead4 −/− blastocysts that formed under these conditions expressed trophectoderm-associated genes. Therefore, TEAD4 is not required for specification of the trophectoderm lineage. Once the trophectoderm was specified, Tead4 was not essential for either proliferation or differentiation of trophoblast cells in culture. However, ablation of Tead4 in trophoblast cells resulted in reduced mitochondrial membrane potential. Moreover, Tead4 suppressed ROS in embryos and embryonic fibroblasts. Finally, ectopically expressed TEAD4 protein could localize to the mitochondria as well as to the nucleus, a property not shared by other members of the TEAD family. These results reveal that TEAD4 plays a crucial role in maintaining energy homeostasis during preimplantation development. KEY WORDS:Tead4, Blastocyst, Trophectoderm, Blastocoel, Oxidative stress, Anti-oxidant, Mouse TEAD4 establishes the energy homeostasis essential for blastocoel formation Kotaro J. Kaneko* and Melvin L. DePamphilis DEVELOPMENT 3681 RESEARCH ARTICLE Tead4 and energy homeostasis that are derived from TE (Tanaka et al., 1998;Yagi et al., 2007). The requirement for TEAD4 during preimplantation development is specific for TE, because Tead4 −/− embryos continue to express genes characteristic of the ICM and can produce embryonic stem cells that are derived from the ICM. Thus, Tead4 is the earliest zygotically expressed transcription factor reported to be essential for blastocoel formation and expression of TE-associated genes. Tead4 might also be required for post-implantation development, because it is expressed selectively in extra-embryonic ectoderm as well as in developing placenta (Jacquemin et al., 1996; Jacquemin et al., 1998).In an effort to understand how TEAD4 specifies TE, we made the surprising discovery that Tead4 −/− embryos could form a blastocoel, express TE-associated genes and produce trophoblast giant cells. Therefore, TEAD4 is not essential for specifying the TE lineage. It is, however, essential for blastocoel formation and expansion, but only under conditions that promote oxidative phosphorylation and therefore oxidative stress. By managing oxidative stress in vitro, the requirement for TEAD4 can be bypassed. In fact, analysis of ectopic Tead4 gene expression as well as ablation of Tead4 gene expression suggested that Tead4 is unique among TEAD members in that TEAD4 can localize to mitochondria and affect mitochondrial activi...

The Hippo pathway effectors TAZ and YAP in development, homeostasis and disease

“…Of note, deletion of either Taz or Yap alone does not result in pre-implantation defects (Hossain et al, 2007;Morin-Kensicki et al, 2006), indicating redundant Taz/Yap activity at this stage of development. Recent work indicates that TEAD4-deficient embryos can develop into properly specified blastocysts when cultured under conditions that alleviate oxidative stress (Kaneko and DePamphilis, 2013). The presence of TEAD4 in the embryo prevents reactive oxygen species (ROS) accumulation, suggesting that this unexplored role might be crucial for early cell fate events.…”

Lineage specification in the mouse preimplantation embryo

“…Although the Hippo/YAP signalling cascade appears to play a central role in TE/ICM specification, the requirement for TEAD4 during TE formation can be bypassed when Tead4 null embryos are cultured in low O 2 conditions, which reduces oxidative stress and mimics the in vivo situation (Kaneko and DePamphilis, 2013). This suggests that YAP can have different DNA-binding partners to activate target genes (Imajo et al, 2015) or that parallel signalling cascades could compensate for the loss of TEAD4 in low O 2 conditions.…”

Metabolism of Preimplantation Embryo Development

“…Glucose, however, is essential for 1-cell embryos to develop to blastocysts, presumably because glucose metabolism is needed not for energy but for alleviation of oxidative stress (ROS) during blastocyst formation. Interestingly, Tead4 À/À 2-cell embryos cannot develop to blastocysts in the absence of glucose, but can form blastocoel by addition of an antioxidant during glucose-free culture (Kaneko & DePamphilis, 2013).…”

“…The prevailing thought is that reduction in [O 2 ] during culture results in reduction of ROS from oxidative processes, such as OXPHOS; this is supported by the observations that inclusion of antioxidants in the culture media ameliorates oxidative stress and improves development. However, O 2 itself appears to be required for preimplantation development as inhibition of OXPHOS or in vitro culture at 1% O 2 inhibits development (Kaneko & DePamphilis, 2013;Thomson, 1967), although this sensitivity may depend on species (Brison & Leese, 1994;Kane & Buckley, 1977). As mentioned earlier, the need for low levels of O 2 by the cleavage-stage embryos likely reflects their primary reliance on monocarboxylates, amino acids, and/or FAs for energy, which can only generate ATP through OXPHOS, although other oxidative processes such as demethylation of methylated CpG dinucleotides by ten-eleven translocation (TET) proteins (Li & Zhang, 2014) cannot be excluded.…”

“…Hence, Tead4 was hypothesized to act upstream of Cdx2 as a specifier of TE lineage. Furthermore, recent report suggests involvement of Hippo signaling pathway in Tead4-mediated TE specification (Nishioka et al, 2009), although exactly how this might occur is not clear (Home et al, 2012;Kaneko & DePamphilis, 2013).…”