An international team of scientists led by Sweden's Karolinska Institutet
has mapped for the first time all the genes that are activated in the first few days of a fertilized human egg. Published in the journal Nature Communications and reported in Bioscience Technology
, the study provides an in-depth understanding of early embryonic development and the key to new therapies against infertility.
The work was supported by the Karolinska Institutet Distinguished Professor Award, the Swedish Research Council, the Strategic Research Program for Diabetes funding at Karolinska Institutet, Stockholm County, the Jane & Aatos Erkko Foundation, the Instrumentarium Science Foundation, and the Åke Wiberg and Magnus Bergvall foundations. The computations were performed on resources provided by SNIC through Uppsala Multidisciplinary Center for Advanced Computational Science (UPPMAX).
At the beginning of a person’s life, there is a single fertilized egg cell. A day after fertilization there are two cells; after two days, four; after three days, eight; and so on, until there are billions of cells at birth. The order in which our genes are activated after fertilization has remained one of the last mysteries of human development.
There are about 23,000 human genes. The current study determined that only 32 of these genes are turned on two days after fertilization. By day three there are 129 activated genes. Seven of the genes found and characterized were not discovered prior to the study.
Principal investigator Juha Kere, professor at the Department of Bio-sciences and Nutrition at Karolinska Institutet and affiliated with the SciLifeLab facility, commented, "These genes are the ignition key that is needed to turn on human embryonic development. It is like dropping a stone into water and then watching the waves spread across the surface."
Outi Hovatta, professor of Obstetrics and Gynaecology at Karolinska Institutet. (Credit: Ulf Sirborn) and a senior author, added, "Our results provide novel insights into the regulation of early embryonic development in human. We identified novel factors that might be used in reprogramming cells into so-called pluripotent stem cells for possible treatment of a range of diseases, and potentially also in the treatment of infertility."
The researchers developed a new way of analyzing the results in order to discover the new genes. While most genes code for proteins, there are a number of repeated DNA sequences often considered to be so-called junk DNA. In fact, they are important in regulating gene expression. The study, a collaboration between three research groups from Sweden and Switzerland that each provided a unique set of skills and expertise, showed that the newly identified genes can interact with the junk DNA and that this is critical to the start of development.