Keeping Egg Cells Fresh with Epigenetics

via dailyaccord.com

"Keeping egg cells in stasis during childhood is a key part of female fertility. New research published today (1st January) in Nature Structural and Molecular Biology sheds some light on the role of epigenetics in placing egg cells into stasis. A team led by Dr Gavin Kelsey in the Babraham Institute and colleagues in Dresden and Munich studied a protein called MLL2 and discovered how it produces a distinctive pattern of epigenetic marks that are needed for egg cell stasis.

A fertilised egg cell is the start of every human life. Yet, egg cells are created inside a woman's body before she is born. The eggs are then kept in stasis throughout childhood until they're needed as an adult. If egg cells don't go into stasis they can't become mature eggs and they will never have the chance to form a new life. Putting an egg cell into stasis involves adding many epigenetic marks throughout its DNA. Epigenetic marks attached to DNA act as footnotes, indicating which genes are turned 'on' or 'off'. 

The scientists wanted to understand where these marks come from in egg cells and how mistakes can cause disease. It is particularly challenging to study epigenetics in egg cells as there are so few of them. The team had to create new, highly sensitive ways to detect epigenetic marks in such small numbers of cells.

Using this approach, they found that, as eggs develop, a mark called H3K4me3 spreads throughout the genome. Scientists have already seen the same mark close to the start of active genes in many cells, but the team discovered that its role in egg cells is different. They showed that the MLL2 protein is responsible for this unusual placement of H3K4me3 in egg cells. Without MLL2, most H3K4me3 marks in egg cells are lost and the cells die before getting the chance to form a new life..."

Learn more:

https://www.sciencedaily.com/releases/2018/01/180101144755.htm

 

Fertilized egg cells trigger, monitor loss of sperm's epigenetic memory

Mouse Zygote | Credit: Image Courtesy
of  Institute of Molecular Biotechnology

"Scientists from the Institute of Molecular Biotechnology (IMBA) in Vienna, Austria, have discovered how an embryo's genomic integrity is safeguarded during the first 24 h after fertilization. Insights into this mechanism have implications for improving in vitro fertilization.

The events triggered when sperm meets an egg are not only life changing for the parents but deeply fascinating from a scientific point of view, too.

The mother of all cells

Following fertilization, DNA from the mother's egg cell and the father's sperm cell constitute the genetic blueprint of the single-cell embryo or zygote. The incoming paternal DNA contains modifications that facilitate an "epigenetic memory" of its sperm state. Proteins provided by the fertilized egg act to largely erase this memory in order to generate a totipotent embryo that can give rise to a whole new individual. 

The mechanisms underlying natural reprogramming to totipotency are remarkably efficient but remain poorly understood. "To put this into perspective, reprogramming to induced pluripotency in cell culture takes several days to weeks whereas reprogramming to totipotency in zygotes occurs in less than 24 h," says Kikuë Tachibana-Konwalski, who devotes her laboratory's research to understanding the molecular secrets of egg cells and zygotes..."

Learn more: 

https://www.sciencedaily.com/releases/2016/12/161201160753.htm

Plastic manufacturing chemical BPS harms egg cells

via acegrease.com

"Bisphenol S, a chemical used to manufacture polycarbonate water bottles and many other products such as epoxy glues and cash receipts, is an increasingly common replacement for bisphenol A, the of which was discontinued because of concerns about its harmful effects on the reproductive system. In a new study, UCLA researchers have found that BPS is just as harmful to the reproductive system as the chemical it replaced. BPS damages a woman's eggs and at lower doses than BPA.

While looking for replacements to toxic chemicals, manufacturers tend to choose substitute chemicals that, while technically different, often share similar physical properties. Due to increasing consumer pressure, companies have replaced BPA with other related compounds now found in many "BPA-free" products. However we do not know how safe these substitutes are. These uncertainties led the researchers to ask whether BPS could impart detrimental effects on reproduction similar to BPA's.

The researchers exposed a common laboratory model, the roundworm, to several concentrations of BPA and/or BPS that approximate the levels of BPA and/or BPS found in humans. They followed the worms through the duration of their reproductive periods and measured their fertility..."

Learn More:

https://www.sciencedaily.com/releases/2016/08/160809170501.htm