Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Fishing games gone wrong - Trial-and-error behind important cause of female infertility

19.08.2011
When an egg cell is being formed, the cellular machinery which separates chromosomes is extremely imprecise at fishing them out of the cell’s interior, scientists at the European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany, have discovered.
The unexpected degree of trial-and-error involved in this process could explain why errors in the number of chromosomes in the egg cell are the leading cause of miscarriages and severe congenital diseases such as trisomies like Down’s syndrome, as well as an important cause of female infertility. The findings are published online today in Cell.

Our cells have two copies of each chromosome, one inherited from our mother and the other from our father. An oocyte, the cell that matures into an egg cell, has to discard half of its chromosomes, keeping only the maternal or paternal copy of each. To do so, fibres called microtubules act like fishing lines, attaching themselves to chromosomes and reeling them in to opposite sides of the cell. However, the EMBL scientists discovered that these microtubules are much worse fishermen than expected, often incorrectly hooking onto a chromosome and having to let it go again.

“We saw that they have to go through several tries before getting the connection right,” says Jan Ellenberg, who led the work at EMBL: “overall, 90% of all chromosomes get connected in the wrong way, and therefore the pathway that corrects these errors is heavily used.”

The difficulty in the oocyte is that two fishing lines cast from opposite sides of the cell have to attach themselves to the maternal and paternal copies of the same chromosome. Each of those chromosome copies has a protein structure called a kinetochore, which acts like the magnet in a toy fish, providing the spot for the microtubule ‘fishing lines’ to attach themselves. The EMBL scientists were the first to track the movement of all kinetochores throughout the whole 8 hours of the first round of cell division in mouse egg cells, which are very similar to human ones.

“We were able to get very high resolution images for extended periods of time,” explains Tomoya Kitajima, who carried out the work, “because our lab developed a microscope that automatically searches for chromosomes, zooms in, and scans only the area they are in, doing very little damage to the cell”.

Children playing magnetic fishing games often accuse others of cheating, using their fishing rod to move a fish into a position that makes it easier to catch. Ellenberg and Kitajima’s time-lapse videos show that fishing microtubules also ‘cheat’ in this way. At earlier stages of cell division, before they start attaching themselves to kinetochores, microtubules interact with the arms of the chromosomes, nudging them into position in a ‘belt’ around the centre of the spindle.

But not even this chromosome belt, which had never been observed before, is enough to ensure that microtubules fish out the chromosomes correctly. The EMBL scientists’ results show that kinetochore attachment is much more error-prone in this type of cell division, called meiosis, than in mitosis, the simpler form of cell division through which other cells in our body split in two. This is probably because the egg cell precursor is an inordinately large cell, and because in meiosis microtubules emanate from around 80 different places in the cell, rather than stemming only from two poles as they do in mitosis.

“Our findings provide a very plausible explanation for the high rate of errors during egg formation. They form the basis to focus our future work on age-related female infertility, as it seems very likely that a component of the pathway that corrects these errors will be involved” Ellenberg concludes.

Kitajima, T.S., Ohsugi, M. & Ellenberg, J. Complete kinetochore tracking reveals error-prone homologous chromosome biorientation in mammalian oocytes.

Published online in Cell on 19 August 2011, DOI 10.1016/j.cell.2011.07.031

Policy regarding use

EMBL press and picture releases including photographs, graphics, movies and videos are copyrighted by EMBL. They may be freely reprinted and distributed for non-commercial use via print, broadcast and electronic media, provided that proper attribution to authors, photographers and designers is made.

Contact:

Lena Raditsch
Head of Communications & Public Relations
European Molecular Biology Laboratory - EMBL
Meyerhofstr. 1
69117 Heidelberg
Germany

T: +49 6221 387 8125
F: +49 6221 387 8525
M:+49 151 14532784
lena.raditsch@embl.de

Lena Raditsch | EMBL Research News
Further information:
http://www.embl.org
http://www.eiroforum.org
http:// www.embl.de/press/2011/110819_Heidelberg

More articles from Life Sciences:

nachricht What the world's tiniest 'monster truck' reveals
23.08.2017 | American Chemical Society

nachricht Treating arthritis with algae
23.08.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

What the world's tiniest 'monster truck' reveals

23.08.2017 | Life Sciences

Treating arthritis with algae

23.08.2017 | Life Sciences

Witnessing turbulent motion in the atmosphere of a distant star

23.08.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>