Differential regulation of H3S10 phosphorylation, mitosis progression and cell fate by Aurora Kinase B and C in mouse preimplantation embryos

Coordination of cell division and cell fate is crucial for the successful development of mammalian early embryos. Aurora kinases are evolutionarily conserved serine/threonine kinases and key regulators of mitosis. Aurora kinase B (AurkB) is ubiquitously expressed while Aurora kinase C (AurkC) is specifically expressed in gametes and preimplantation embryos. We found that increasing AurkC level in one blastomere of the 2-cell embryo accelerated cell division and decreasing AurkC level slowed down mitosis. Changing AurkB level had the opposite effect. The kinase domains of AurkB and AurkC were responsible for their different ability to phosphorylate Histone H3 Serine 10 (H3S10P) and regulate metaphase timing. Using an Oct4-photoactivatable GFP fusion protein (Oct4-paGFP) and fluorescence decay after photoactivation assay, we found that AurkB overexpression reduced Oct4 retention in the nucleus. Finally, we show that blastomeres with higher AurkC level elevated pluripotency gene expression, which were inclined to enter the inner cell mass lineage and subsequently contributed to the embryo proper. Collectively, our results are the first demonstration that the activity of mitotic kinases can influence cell fate decisions in mammalian preimplantation embryos and have important implications to assisted reproduction.

Effect of gonadotropins on chromosome aneuploidy, chromosome mosaicism & sex ratio in mouse preimplantation embryos.

Background & objectives: There are potential risks of major birth defect in IVF (in vitro fertilization) pregnancy as well as IVF-ICSI (intra cytoplasmic sperm injection) pregnancies in comparison with naturally conceived human pregnancies. This increase risk could be due to either gonadotropins used for ovarian stimulation or in vitro culture conditions or multiple pregnancy or combinations of all the factors. The effects of gonadotropins on chromosome aneuploidy, chromosome mosaicism and sex ratio on mouse preimplantation embryos were evaluated through the use of fl uorescence in situ hybridization (FISH). Methods: The study material consisted of 111 preimplantation mouse embryos (2-16 cell stage) in control group and 405 preimplantation mouse embryos in gonadotropin stimulated group from genetically identical Swiss Albino young (6-8 wk) mouse kept in a similar environmental conditions. The study was designed to investigate effect of gonadotropins on chromosome aneuploidy, chromosome mosaicism and sex ratio through the use of FISH technique using chromosome X, Y and 19 probes. All blastomeres of embryos in both groups were assessed. Results: Interpretable FISH results were obtained in 66 embryos in control group and 128 embryos in gonadotropin stimulated group. There was no excess of chromosome aneuploidy (only one case of sex chromosome trisomy in study group; 19, 19, X, Y, Y) or chromosome mosaicism or deviations in sex ratio between the two groups. However, deviation (1.36 M: 1 F in control group & 1.25 M : 1 F in study group) was seen from expected sex ratio (1 M : 1 F) i.e., skewed sex ratio in both the groups. Interpretation & conclusions: Our results showed that gonadotropins used for ovarian stimulation had no effects in causing increase in chromosome X, Y, 19 aneuploidy and mosaicism and skewing of sex ratio in mouse model. A large scale study with more FISH probes on a larger sample size need to be done to confi rm the findings.

Effects of Vero Cells Co-culture System on The In Vitro Development of Mouse Preimplantation Embryos in Media with Different Composition of Glucose and Pyruvate / 대한산부인과학회지

OBJECTIVE: The purpose of this study was to examine the effects of vero cells co-culture system on the in vitro development of mouse preimplantation embryos in culture media with different composition of glucose and pyruvate. METHODS: Two-cell embryos were collected from 4-5 weeks old ICR mice. Seven hundreds twenty two embryos were cultured with or without vero cells monolayer in four media with different compositions that was manufactured by two DMEM media with (DMEM-GGP) or without (DMEM-G) glucose and pyruvate. In control, DMEM-G medium which is currently using for human embryo culture in our infertility clinic was used. Group I (DMEM-G(1/4)GP) was cultured in medium which was mixed three volume of DMEM-G and one volume of DMEM-GGP, and group II (DMEM-G(1/2)GP) was cultured in medium which was mixed same volume of DMEM-G and DMEM-GGP, and group III was cultured in DMEM-GGP. All media were added to 20% hFF. Results between different groups were analyzed using a Chi-square test, and considered statistically significant when p value was less than 0.05. RESULTS: The developmental rate into 3-cell