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

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Supersensitive through quantum entanglement

28.06.2017 | Physics and Astronomy

X-ray photoelectron spectroscopy under real ambient pressure conditions

28.06.2017 | Physics and Astronomy

Mice provide insight into genetics of autism spectrum disorders

28.06.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>