PhD Scientific Days 2023

Molecular Sciences III.

mRNA sequencing of preimplantation murine embryos in relation to light exposure

Text of the abstract

Introduction
During Assisted Reproductive Technologies (ART) the embryos are exposed to light. Depending on its wavelength, light affects cell function. Longer wavelengths (> 600 nm) have positive effects, including increased cell proliferation and the suppression of apoptotic pathways. In contrast, shorter wavelengths (<450 nm) cause cellular damage, including elevated ROS production and mitochondrial dysfunction.
Earlier our research group investigated the relationship between light exposure and the developmental- and implantation capacity of mouse embryos. In vitro cultured embryos were exposed to white or red filtered light, and then embryo growth, DNA fragmentation and implantation capacity were monitored. Implantation was significantly reduced after white light exposure, which may have been caused by increased DNA fragmentation and apoptosis.
Aims
Determination of the transcriptome of preimplantation murine embryos in relation to light exposure.
Methods
In the present study, we used new generation sequencing to determine the mRNA content and differential expression analysis to quantify the gene expression profiles after light exposure.
Results
Marked differences were detected in the transcriptomes of embryos exposed to either white or red light. The most prominent change was the activation of the extrinsic apoptotic pathways in the white light exposed group, while the red light illumination increased the translational processes, DNA repair and cytoskeleton reorganization.
Conclusion
Visible light does not cause directly DNA breaks, however, due to the induction of increased ROS production, it can have a role in the development of DNA damage. Mitochondria show increased activity in rapidly dividing embryonic cells and their intact function is indispensable to a successful implantation. Therefore, after fertilization, embryos are highly sensitive to effects that affect mitochondria. The cytochrome c oxidase enzyme is light sensitive, therefore we hypothesize that 1) mitochondria may be the targets of light, and 2) light exposure induced increased ROS production has a role in DNA damage.
In summary, red light-induced cellular processes are shifted towards cellular regeneration, including DNA repair mechanisms and anabolic processes, while the white light shifts the balance towards apoptosis.
Funding
The funding was provided by STIA 2017 Semmelweis University.