The potential role of Annexin 3 in diapause embryo restart of Artemia sinica and in response to stress of low temperature.

Annexins are highly conserved and ubiquitous in various somatic cell types. They are involved in membrane transport and a range of calcium-regulated activities on the cell membrane surface, including vesicular transport, membrane fusion in exocytosis, signal transduction, and formation of calcium channels. They also regulate inflammatory response, cell differentiation, and interaction between cytoskeletal proteins. In this study, for the first time, an ANX3 gene from Artemia sinica ( As-anx3) was cloned. The As-anx3 full-length complementary DNA comprises 1,024 bp and has a 948 bp open reading frame encoding a 315-amino-acid polypeptide with four ANX domains. The profiles of both As-ANX3 mRNA and protein expression exhibited peaks at the 0 hr stage and had the same significant downregulation trend throughout the post-diapause embryo development stage. The ERK1/2, the phosphorylation levels of ERK1/2, and cell cycle-related protein (CDK4) expressions were analyzed by western blot analysis. The results showed that CDK4 presented a significantly ascending trend from 0 and 40 hr, although the phosphorylation levels of ERK1/2 did not increase significantly. The transcriptional and protein expressions of As-ANX3 were highly upregulated when the temperature was lowered from 25 to 15°C, but the expressions showed a gradual downward trend when the temperature was further lowered to 5°C. These results indicated that As-ANX3 plays a crucial role in restarting diapause and low-temperature stress in A. sinica.

Impaired imprinted X chromosome inactivation is responsible for the skewed sex ratio following in vitro fertilization.

Dynamic epigenetic reprogramming occurs during normal embryonic development at the preimplantation stage. Erroneous epigenetic modifications due to environmental perturbations such as manipulation and culture of embryos during in vitro fertilization (IVF) are linked to various short- or long-term consequences. Among these, the skewed sex ratio, an indicator of reproductive hazards, was reported in bovine and porcine embryos and even human IVF newborns. However, since the first case of sex skewing reported in 1991, the underlying mechanisms remain unclear. We reported herein that sex ratio is skewed in mouse IVF offspring, and this was a result of female-biased peri-implantation developmental defects that were originated from impaired imprinted X chromosome inactivation (iXCI) through reduced ring finger protein 12 (Rnf12)/X-inactive specific transcript (Xist) expression. Compensation of impaired iXCI by overexpression of Rnf12 to up-regulate Xist significantly rescued female-biased developmental defects and corrected sex ratio in IVF offspring. Moreover, supplementation of an epigenetic modulator retinoic acid in embryo culture medium up-regulated Rnf12/Xist expression, improved iXCI, and successfully redeemed the skewed sex ratio to nearly 50% in mouse IVF offspring. Thus, our data show that iXCI is one of the major epigenetic barriers for the developmental competence of female embryos during preimplantation stage, and targeting erroneous epigenetic modifications may provide a potential approach for preventing IVF-associated complications.

Actin Disorganization Plays a Vital Role in Impaired Embryonic Development of In Vitro-Produced Mouse Preimplantation Embryos.

Assisted reproductive technology (ART) is being increasingly applied to overcome infertility. However, the in vitro production process, the main procedure of ART, can lead to aberrant embryonic development and health-related problems in offspring. Understanding the mechanisms underlying the ART-induced side effects is important to improve the ART process. In this study, we carried out comparative transcriptome profiling between in vivo- (IVO) and in vitro- produced (IVP) mouse blastocysts. Our results suggested that aberrant actin organization might be a major factor contributing to the impaired development of IVP embryos. To test this, we examined the effect of actin disorganization on the development of IVP preimplantation embryos. Specific disruption of actin organization by cytochalasin B (CB) indicated that well-organized actin is essential for in vitro embryonic development. Supplementing the culture medium with 10(-9) M melatonin, a cytoskeletal modulator in adult somatic cells, significantly reversed the disrupted expression patterns of genes related to actin organization, including Arhgef2, Bcl2, Coro2b, Flnc, and Palld. Immunofluorescence analysis showed that melatonin treatment of IVP embryos significantly improved the distribution and organization of actin filaments (F-actin) from the 8-cell stage onwards. More importantly, we found that melatonin alleviated the CB-mediated aberrant F-actin distribution and organization and rescued CB-induced impaired embryonic development. This is the first study to indicate that actin disorganization is implicated in impaired development of IVP embryos during the preimplantation stage. We also demonstrated that improving actin organization is a promising strategy to optimize existing IVP systems.