Studying p38-MAPK – A signaling pathway in mice embryos

Agrima Bhatt, Rajasthan University

In previous studies, p38-MAPK was identified as a regulator for blastocyst ICM fate in the mouse embryo. Today, scientists are trying to find out the functional role of the DDX21 protein.

For the understanding of this complex pathway, let’s first deep dive into the embryo and its development stages. Fusion of male and female gametes, resulting in zygote formation is the beginning stage for the preimplantation period of mouse embryo development. The zygote which is at the one-cell stage undergoes continuous cell cleavage divisions. It undergoes division under the zona pellucida which is a protective shell, without altering any of its cytoplasmic volumes. 

Thus, preimplantation development undergoes a series of stages through which blastomeres, progressively smaller cells, keep on dividing. This stage is known as the blastocyst-stage embryo, which can undergo uterine implantation. The mouse embryo emerges from the outer membrane after the seven cell divisions also known as cleavage. This embryo development is initiated by an endogenous factor responsible for a cascade of events associated with specific cell cycles. The blastocyst at the implantation stage consists of an epithelial membrane made up of trophectoderm cells. These cells cover a fluid-filled cavity and the inner cell mass (ICM).

These series of events in early mouse development are still being investigated by researchers. Through synthetic manipulation in cell number and tissue mass, mouse embryos are subjected to constant experimentation.  

What is preimplantation embryonic development?

It is the phase of a mammal’s life between fusion of gametes i.e., fertilization and uterine implantation. This phase encompasses crucial events like zygotic genome activation (ZGA), division of cells, and lineage specification. Recently, a well-put-together approach has been seen developing in preimplantation embryonic development by including genetic events like translation. This event is crucial to initiate and control pluripotency, thus allowing the diapause stage in the embryo.  

p38-MAPK – A Signaling Pathway:

This signaling pathway is still a question mark in many minds of scientists around the globe. Its functional role in the preimplantation stage remains a mystery to uncover. In earlier stages, p38-MAPK activity is responsible for the formation of the actin filament. It was also found to be responsible for other series of events to enable the expansion of the blastocoel cavity. 

Recent research has been mainly focused on the maturation of blastocyst and ICM specification. In the study in discussion, however, p38-MAPK was investigated for the regulatory role of protein translation. Scientists attempted DDX21 which is an RNA helicase known for regulation in rRNA processing about preimplantation mouse embryo development. DDX21 protein was produced from the 16-cell stage forward, becoming predominantly nucleolar throughout blastocyst maturation, heavily dependent on active p38-MAPK.

Embryo Culture and Analysis:

Experimentation with mouse lines and embryo culture was done following all guidelines imperative for animal experiments. 2-cell stage embryos were then isolated after successful mating and were further cultured on artificial media. Embryos were then immobilized using microinjection methods followed by staining with immunofluorescence and visualization using microscopy. With the help of microinjections, embryos were further processed for RNA extraction and isolation. 

DDX21 Protein Expression Significance:

DDX21 protein was studied thoroughly by researchers during the preimplantation developmental stages. After immunofluorescent staining, DDX21 protein was expressed at the basal levels of nuclei and 8-celled stage embryos. Its expression was also revealed at the 16-celled embryo stage i.e., the later blastocyst stage. The structure of the DDX21 protein was found to vary greatly before and after the formation of the blastocyst cavity. It was found to be pan-nucleoplasmic in pre-cavity embryos as compared to nucleolar after cavity formation. Researchers have concluded that there is a correlation between the significance of such protein with blastocyst formation.

Also read: Mullerian mimicry in animals- An interesting concept!

Reference:

1. Bora, P., Gahurova, L., Hauserova, A., Stiborova, M., Collier, R., Potěšil, D., Zdráhal, Z., & Bruce, A. W. (2021). DDX21 is a p38-MAPK-sensitive nucleolar protein necessary for mouse preimplantation embryo development and cell-fate specification. Open Biology, 11(7), 210092. https://doi.org/10.1098/rsob.210092

• The Corrosion Prediction from the Corrosion Product Performance
• Nitrogen Resilience in Waterlogged Soybean plants
• Cell Senescence in Type II Diabetes: Therapeutic Potential
• Transgene-Free Canker-Resistant Citrus sinensis with Cas12/RNP
• AI Literacy in Early Childhood Education: Challenges and Opportunities

Author’s info:

Agrima Bhatt is an undergraduate student studying BSc. Biotechnology in Jaipur, Rajasthan. She is a science and research enthusiast who also loves to write articles and short snippets.

Some of her published articles at BioXone are:

1. https://bioxone.in/news/worldnews/molecular-mechanisms-underlying-virescent-mutation-in-cotton/
2. https://bioxone.in/news/worldnews/multi-angle-projection-microscope-a-novel-imaging-technique/
3. https://bioxone.in/news/worldnews/scientists-develop-novel-cholera-vaccine-from-rice-grains/
4. https://bioxone.in/news/worldnews/ai-predicts-the-relation-between-viruses-and-mammals/