Involvement of the p110α isoform of PI3K in early development of mouse embryos

Fetal and trophoblast PI3K p110α have distinct roles in regulating resource supply to the growing fetus in mice

Studies suggest that placental nutrient supply adapts according to fetal demands. However, signaling events underlying placental adaptations remain unknown. Here we demonstrate that phosphoinositide 3-kinase p110α in the fetus and the trophoblast interplay to regulate placental nutrient supply and fetal growth. Complete loss of fetal p110α caused embryonic death, whilst heterozygous loss resulted in fetal growth restriction and impaired placental formation and nutrient transport. Loss of trophoblast p110α resulted in viable fetuses, abnormal placental development and a failure of the placenta to transport sufficient nutrients to match fetal demands for growth. Using RNA-seq we identified genes downstream of p110α in the trophoblast that are important in adapting placental phenotype. Using CRISPR/Cas9 we showed loss of p110α differentially affects gene expression in trophoblast and embryonic stem cells. Our findings reveal important, but distinct roles for p110α in the different compartments of the conceptus, which control fetal resource acquisition and growth.

Musashi 1-positive cells derived from mouse embryonic stem cells treated with LY294002 are prone to differentiate into intestinal epithelial-like tissues

The majority of Musashi 1 (Msi1)‑positive cells derived from mouse embryonic stem cells (mESCs) are prone to differentiate into neural epithelial‑like cells, and only a small proportion of Msi1‑positive cells differentiate into intestinal epithelial‑like cells. Whether inhibiting the phosphatidylinositol 3‑kinase (PI3K) signaling of mESCs can promote the differentiation of Msi1‑positive cells into intestinal epithelial‑like cells remains to be fully elucidated. In the present study, to inhibit PI3K signaling, mESCs were treated with LY294002. A pMsi1‑green fluorescence protein reporter plasmid was used to sort the Msi1‑positive cells from mESCs treated and untreated with LY294002 (5 µmol/l). The Msi1‑positive cells were hypodermically engrafted into the backs of non‑obese diabetic/severe combined immunodeficient mice. The presence of neural and intestinal epithelial‑like cells in the grafts was detected by reverse transcription‑quantitative polymerase chain reaction analysis and immunohistochemistry. Compared with the Msi1‑positive cells derived from mESCs without LY294002 treatment, Msi1‑positive cells derived from mESCs treated with LY294002 expressed higher levels of leucine‑rich repeat‑containing G‑protein coupled receptor, a marker of intestinal epithelial stem cells, and lower levels of Nestin, a marker of neural epithelial stem cells. The grafts from Msi1‑positive cells treated with LY294002 contained more intestinal epithelial‑like tissues and fewer neural epithelial‑like tissues, compared with those from untreated Msi1‑positive cells. LY294002 had the ability to promote the differentiation of mESCs into intestinal epithelial‑like tissues. The Msi1‑positive cells selected from the cell population derived from mESCs treated with LY294002 exhibited more characteristics of intestinal epithelial stem cells than those from the untreated group.

How PI3K-derived lipids control cell division

To succeed in cell division, intense cytoskeletal and membrane remodeling are required to allow accurate chromosome segregation and cytoplasm partitioning. Spatial restriction of the actin dynamics and vesicle trafficking define the cell symmetry and equivalent membrane scission events, respectively. Protein complexes coordinating mitosis are recruited to membrane microdomains characterized by the presence of the phosphatidylinositol lipid members (PtdIns), like PtdIns(3,4,5)P₃,PtdIns(4,5)P₂, and PtdIns(3)P. These PtdIns represent a minor component of cell membranes, defining membrane domain identity, ultimately controlling cytoskeleton and membrane dynamics during mitosis. The coordinated presence of PtdIns(3,4,5)P₃ at the cell poles and PtdIns(4,5)P₂ at the cleavage furrow controls the polarity of the actin cytoskeleton leading to symmetrical cell division. In the endosomal compartment, the trafficking of PtdIns(3)P positive vesicles allows the recruitment of the protein machinery required for the abscission.

Differential glycolytic and glycogenogenic transduction pathways in male and female bovine embryos produced in vitro

Previous studies have shown that developmental kinetic rates following IVF are lower in female than in male blastocysts and that this may be related to differences in glucose metabolism. In addition, an inhibition of phosphatidylinositol 3-kinase (PI3-K) inhibits glucose uptake in murine blastocysts. Therefore, the aim of this study was to identify and compare the expression of proteins involved in glucose metabolism (hexokinase-I, HK-I; phosphofructokinase-1, PFK-1; pyruvate kinase 1/2, PK1/2; glyceraldehyde-3-phosphate dehydrogenase, GAPDH; glucose transporter-1, GLUT-1; and glycogen synthase kinase-3, GSK-3) in male and female bovine blastocysts to determine whether PI3-K has a role in the regulation of the expression of these proteins. Hexokinase-I, PFK-1, PK1/2, GAPDH and GLUT-1 were present in bovine embryos. Protein expression of these proteins and GSK-3 was significantly higher in male compared with female blastocysts. Inhibition of PI3-K with LY294002 significantly decreased the expression of HK-I, PFK-1, GAPDH, GSK-3A/B and GLUT-1. Results showed that the expression of glycolytic proteins HK-I, PFK-1, GAPDH and PK1/2, and the transporters GLUT-1 and GSK-3 is regulated by PI3-K in bovine blastocysts. Moreover, the differential protein expression observed between male and female blastocysts might explain the faster developmental kinetics seen in males, as the expression of main proteins involved in glycolysis and glycogenogenesis was significantly higher in male than female bovine embryos and also could explain the sensitivity of male embryos to a high concentration of glucose, as a positive correlation between GLUT-1 expression and glucose uptake in embryos has been demonstrated.

Identification and regulation of glycogen synthase kinase-3 during bovine embryo development

The aim of this study was to examine the presence and regulation of glycogen synthase kinase-3alpha (GSK3A) and GSK-3beta (GSK3B) in bovine embryos and their possible roles in embryo development. Our results show that GSK3A and GSK3B are present in bovine embryos at the two-cell stage to the hatched blastocyst stage. Bovine embryo development was associated with an increase in the phosphorylation of both isoforms, being statistically significant at blastocyst and hatched blastocyst stages, compared with earlier stages. Inhibition of GSK3 with CT99021 (3 microM) resulted in a significant increase in the percentage and quality of blastocysts, while inhibition of GSK3 with lithium chloride (LiCl; 20 mM) significantly reduced at the proportion of eight-cell embryos on day 3 and inhibited blastocyst formation. The use of LY294002 (10 microM), a specific inhibitor of phosphatidylinositol-3 kinase, also produced a significant decrease in embryo development. In addition, treatment with LiCl and LY294002 produced a significant decrease in the serine phosphorylation of both isoforms of GSK3. Finally, CT99021 and LiCl reduced the phosphorylation of beta-catenin on Ser45 in two-cell embryos, while LY294002 increased it. Despite the fact that LiCl inhibited GSK3 activity, as demonstrated by beta-catenin phosphorylation, its effects on the bovine embryo could be mediated through other signaling pathways leading finally to a decrease in the phosphorylation of GSK3 and a reduction in embryo development. Therefore, in conclusion, GSK3A/B serine phosphorylation was positively correlated with embryo development, indicating the importance of an accurate regulation of GSK3 activity during developmental stages to achieve normal bovine embryo development.

Characterization of p70 S6 kinase 1 in early development of mouse embryos

The mTOR kinase controls cell growth, proliferation, and survival through two distinct multiprotein complexes mTORC1 and mTORC2. p70 S6 Kinase 1 (S6K1) is characterized as downstream effector of mTOR. Until recently, the connection between S6K1 and mTORC1 /mTORC2 during the early development of mouse embryos has not been well elucidated. Here, the expression level of total S6K1 and its phosphorylation at Thr389 was determined in four phases of one-cell embryos. S6K1 was active throughout the cell cycle especially with higher activity in G2 and M phases. Rapamycin decreased the activity of M-phase promoting factor (MPF) and delayed the first mitotic cleavage. Down-regulating mTOR and raptor reduced S6K1 phosphorylation at Thr389 in one-cell embryos. Furthermore, rapamycin and microinjection of raptor shRNA decreased the immunofluorescent staining of Thr389 phospho-S6K1. It is proposed that mTORC1 may be involved in the control of MPF by regulating S6K1 during the early development of mouse embryos.