Preimplantation Embryo Development in the Mouse Requires the Latency of TRP53 Expression, Which Is Induced by a Ligand-Activated PI3 Kinase/AKT/MDM2-Mediated Signaling Pathway1

Abstract

A universal response to cellular stress is the expression of transformation-related protein 53 (TRP53). This transcription factor reduces cell proliferation and/or survival and is classed as a tumour suppressor protein. Several stresses (including culture) cause increased TRP53 expression in blastocysts and their reduced long-term developmental potential. This study shows that culture from the zygote stage (but not the 2-cell stage) reduced the development of C57BL6 inbred (but not hybrid) strain mouse embryos. Reduced viability was TRP53 dependent, being partially reversed by a TRP53 inhibitor (Pifithrin-alpha). However, the presence of culture did not cause an increase in Trp53 mRNA levels (levels were reduced following culture, P , 0.001). Transformed mouse 3T3 cell double minute 2 (MDM2) causes the ubiquitination and degradation of TRP53. MDM2 activation is accompanied by phosphorylation of Ser-166, and this is commonly catalyzed by the phosphatidylinositol-3 kinase and RAC-alpha serine/threonine-protein kinase (AKT) signaling pathway. Paf is an autocrine embryotrophin that activates the phosphatidylinositol-3 kinase/AKT pathway. High levels of TRP53 expression occurred following the culture of zygotes lacking the Paf receptor (Ptafr À/À ) and following inhibition of phosphatidylinositol-3 kinase or AKT. Inhibition of MDM2 caused a Trp53-dependent reduction in zygote development. Inbred strain embryos cultured from the zygote stage expressed less phosphorylated MDM2 than similar embryos collected from the uterus. The addition of Paf to the media caused increased phosphorylation of MDM2, and this was blocked by inhibitors of phosphatidylinositol-3 kinase and AKT. The study identifies trophic ligand signaling via the activation of phosphatidylinositol-3 kinase and AKT as a mechanism resulting in the activation of MDM2.

CFTR mediates bicarbonate-dependent activation of miR-125b in preimplantation embryo development

“…Stress-induced upregulation of p53 has been shown to result in developmental arrest of preimplantation embryo [44]. The latency of p53 in preimplantation embryo is well-documented to be maintained by autocrine stimulation through PI3K/Akt/Mdm2 pathway [43]. In this study, we have demonstrated an alternative pathway regulating the latency of p53 through HCO 3 − /CFTR-dependent miR-125b activation.…”

“…The HCO 3 − -dependent miR-125b activation is physiologically important for early embryo development by targeting p53 and its downstream target p21. It has been previously demonstrated that the latency of p53 is required for normal preimplantation embryo development [43]. Stress-induced upregulation of p53 has been shown to result in developmental arrest of preimplantation embryo [44].…”

“…A recent study has found that miR-125b is a novel negative regulator of p53 [15]. Preimplantation embryo development has been shown to require the latency of p53 [36] and increased expression of p53 is associated with poor developmental potential of preimplantation embryos [37]. Therefore, we tested whether downregulation of miR-125b by removal − and CFTR inhibition was rescued by injection of miR-125b precursor (pre-miR-125b) (n = 3); HCO 3 − free + pre-miR-nc group: four-cell (15/62 embryos), blastocyst (0/62 embryos); HCO 3 − free + pre-miR-125b group: four-cell (36/61 embryos), blastocyst (21/60 embryos); Vehicle + pre-miR-nc group: four-cell (46/60 embryos), blastocyst (25/60 embryos); Vehicle + pre-miR-125b group: four-cell (55/64 embryos), blastocyst (38/64 embryos); CFTRinh172 + pre-miR-nc group: four-cell (10/60 embryos), blastocyst (0/60 embryos); CFTRinh172 + pre-miR-125b group: four-cell (33/63 embryos), blastocyst (19/63 embryos).…”

Embryo-endometrial interactions during early development after embryonic diapause in the marsupial tammar wallaby

“…PAF may be important for implantation and maternal recognition of pregnancy (O'Neill, 1991) and enhances mitoses in preimplantation embryos in mice (Roberts et al, 1993). Paf generates a pro-survival anti-apoptotic transcriptome within the embryo (Jin and O'Neill, 2011) and maintains the tumour suppressor protein P53 in a latent state (Jin et al, 2009). In the tammar, PAF is present in the culture media after incubation of endometrial explants during embryonic diapause and at all reactivation stages examined (Kojima et al, 1993).…”

Paf receptor expression in the marsupial embryo and endometrium during embryonic diapause

“…In the mouse, the addition of Paf can stimulate embryo metabolism (Ryan et al 1989(Ryan et al , 1990a, increase total cell number (Ryan et al 1990b, Roudebush et al 1996 and promote overall embryo development and viability (Nishi et al 1995, Stoddart et al 1996, O'Neill 1997, 1998. Furthermore, Paf has the critical function of generating a pro-survival antiapoptotic transcriptome within the embryo (Jin & O'Neill 2011) and has the net effect of maintaining the tumour suppressor protein p53 in a latent state (Jin et al 2009). However, exposure to high levels of Paf provides either no additional benefit or can even have harmful effects (Ryan et al 1990b).…”