A team of scientists at the Helmholtz Zentrum Mü nchen shows changes in the immediate environment associated with DNA after the ovum and sperm fuse to form the particular zygote. The results suggest why all conceivable somatic tissue can develop from the germ cells. The study has been published within the journal Genes and Development .

Months before the often-cited miracle associated with birth occurs, numerous events take place that science nevertheless does not completely understand. For instance, this includes the question of how just one cell can be the origin of all subsequent cells in the future patient. Exploring how this is possible is the objective of Prof. Dr . Maria-Elena Torres-Padilla, Director of the Institute of Epigenetics and Stem Cells (IES) at the Helmholtz Zentrum Mü nchen and Professor for stem cell biology in the Ludwig-Maximilians-Universitä t Munich.

“We are especially interested in the events that are required when the cells are usually to divide so many times and develop in so many different methods, for example cells from the skin, and the liver, and the center, ” the researcher explains. In a current study, the lady and her team approached this problem by examining the particular so-called chromatin, which refers to the DNA and the aminoacids (histones) around it. “We looked at how certain histones are changed after fertilization, which allowed us to describe a new mechanism. ”

Small accessories, big effects

The authors found that the molecule Suv4-20h2, a so-called histone methyltransferase, moves over the chromatin and attaches small chemical changes (dubbed methyl groups) to the histones. When the addition of these chemical substance changes occurs, the cell is constrained in its department and development, Torres-Padilla explains. But once fertilization takes place, the attachments disappear and the fertilised ovum can develop right into a new organism.

In order to confirm these outcomes, the researchers used an experimental model to test the result of keeping the Suv4-20h2 active in the fertilized ovum. “We were able to demonstrate that in this case, the methyl groups stick to the histones, ” explains first author Andre Eid, doctoral candidate at the IES. “This arrests the growth and the cells did not progress beyond the first division. inch

In further experiments, the team could show that this mechanism is probably based on the fact that the methyl groups on the histones lead to a defect during the copying of the genetic material, referred to as replication. This defect leads to then a replication ‘check point’, whereby the cell period comes to a standstill.

“Our results have provided us insight into the complex connections between the chromatin as well as the ability of cells to develop into other types of cellular material — so-called totipotency, ” Torres-Padilla states as the lady puts the results into perspective. This is an important step each for human embryology and for the understanding of certain malignancies in which the cells display very similar mechanisms that affect their own rate of growth.