This activity can be dangerous, however, especially when it arises in cells that produce eggs and sperm. Such changes can threaten the offspring and the success of a species.
To ensure the integrity of these cells, nature developed a mechanism to quash this genetic scrambling, but how it works has remained a mystery. Now a team of scientists, including researchers at the Carnegie Institution's Department of Embryology, has identified a key protein that suppresses jumping genes in mouse sperm and found that the protein is vital to sperm formation.
"There is a tiny cell component that is unique to germ cells—the precursors to egg and sperm—called nuage, which means 'cloud' in French. Other researchers recently suspected that nuage was involved in keeping genes from jumping around in germ cells of the female fruit fly," explained Carnegie's Alex Bortvin, a senior author of the study. "But until this mouse study, no one knew for sure if it was involved in mammalian germ cells. To test if the mouse nuage played a similar role in mammals, we focused on a mouse protein called Maelstrom whose distant relative protein in the fruit fly was implicated in the other study."
In this research, published in the August 12th issue of Developmental Cell, the scientists first looked at where the protein Maelstrom resides during the formation of sperm. By marking the protein with a fluorescent antibody, they found that it was predominantly located in the cytoplasm, near the nucleus of the germ cell, at the nuage. To understand what Maelstrom does during the formation of sperm, the scientists created mutant mice that did not have the gene to produce the Maelstrom protein.
"We found that without the gene the process of meiosis was severely impaired," said Bortvin. "There was a profound defect in interactions of parental chromosomes, a process known as synapsis, leading to death of germ cells. This was clear evidence that the protein is vital to the formation of sperm."
The cause of such a defect became apparent when the researches looked at the behavior of transposons. "We observed massive flooding of the cytoplasm and nuclei of germ cells by transposons in the mutant mice," said Godfried van der Heijden, a Carnegie postdoctoral fellow and co-author. "This was the first time such a phenomenon was observed in germ cells of any species. Moreover, we found that the more transposons present in the nucleus, the more likely parental chromosomes would fail to locate each other during synapsis. Clearly, uncontrolled activity of jumping genes causes chromosomal mayhem in germ cells. Our results, coupled with work by Toshie Kai, a former Carnegie researcher studying the role of nuage in egg development in the fruit fly, suggest that nuage plays a central role in transposon silencing during the development of egg and sperm of many species from insects to mammals. "
The last surprise for the scientists was the observation that, contrary to the current view in the field, the silencing of jumping genes does not occur one time only in male germ cells during the mouse fetal development. Instead, every time a germline stem cell divides by meiosis to make sperm in adults the jumping genes are activated only to be silenced soon thereafter.
"This was a very puzzling finding," commented Bortvin. "Since the jumping genes are not silenced just once during the development of the fetus, but every time new sperm are produced during a mouse life, it's possible that germ cells may employ transposons in some fundamental way in male germline meiosis. This research is the first such clue of that possibility. We will be very busy over the next few years trying to crack this and other puzzles of Maelstrom's role in controlling meiosis and sperm production."
Closing the carbon loop
08.12.2016 | University of Pittsburgh
Newly discovered bacteria-binding protein in the intestine
08.12.2016 | University of Gothenburg
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
08.12.2016 | Life Sciences
08.12.2016 | Physics and Astronomy
08.12.2016 | Materials Sciences