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Sunday, July 30, 2017

Mother's epigenetic memory is essential for the development and survival of the new generation.

The Minding Brain
Epigenetic mechanisms modulated by envir...onmental cues such as diet, disease or our lifestyle take a major role in regulating the DNA by switching genes on and off. Epigenetic marks transmitted from the mother are a fine-tuned mechanism to control gene activation during the complex process of early embryogenesis
It has long been thought that these epigenetic modifications never cross the border of generations. Scientists assumed that epigenetic memory accumulated throughout life is entirely cleared during the development of sperms and egg cells.
Just recently a handful of studies stirred the scientific community by showing that epigenetic marks indeed can be transmitted over generations, but exactly how, and what effects these genetic modifications have in the offspring is not yet understood.
It has been long debated if epigenetic modifications accumulated throughout the entire life can cross the border of generations and be inherited to children or even grand children.
Now researchers from the Max Planck Institute of Immunobiology and Epigenetics in Freiburg show robust evidence that not only the inherited DNA itself but also the inherited epigenetic instructions contribute in regulating gene expression in the offspring.
They discovered that embryos lacking H3K27me3 during early development could not develop to the end of embryogenesis. "It turned out that, in reproduction, epigenetic information is not only inherited from one generation to another but also important for the development of the embryo itself,"
It seems, virtually, that inherited epigenetic information is needed to process and correctly transcribe the genetic code of the embryo," explains Fides Zenk.
In our body we find more than 250 different cell types. They all contain the exact same DNA bases in exactly the same order; however, liver or nerve cells look very different and have different skills. What makes the difference is a process called epigenetics.
Epigenetic modifications label specific regions of the DNA to attract or keep away proteins that activate genes. Thus, these modifications create, step by step, the typical patterns of active and inactive DNA sequences for each cell type.
Moreover, contrary to the fixed sequence of 'letters' in our DNA, epigenetic marks can also change throughout our life and in response to our environment or lifestyle. For example, smoking changes the epigenetic makeup of lung cells, eventually leading to cancer. Other influences of external stimuli like stress, disease or diet are also supposed to be stored in the epigenetic memory of cells.
At the Max Planck Institute of Immunobiology and Epigenetics in Freiburg, Germany used fruit flies to explore how epigenetic modifications are transmitted from the mother to the embryo
The Max Planck researchers found that H3K27me3 modifications labeling chromatin DNA in the mother's egg cells were still present in the embryo after fertilization, even though other epigenetic marks are erased. "This indicates that the mother passes on her epigenetic marks to her offspring. But we were also interested, if those marks are doing something important in the embryo,"
Our study indicates that we inherit more than just genes from our parents. It seems to be that we also get a fine-tuned as well as important gene regulation machinery that can be influenced by our environment and individual lifestyle