Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Actin moves chromosomes: Discovery changes fundamental thinking

14.07.2005


Microtubules need a helping hand to find chromosomes in dividing egg cells, scientists have discovered. Although it was generally accepted that microtubules act alone as the cellular ropes to pull chromosomes into place, a new study by researchers at the European Molecular Biology Laboratory (EMBL) shows that this is not the case. They found that in large cells such as animal eggs, something else is needed to move the chromosomes into the correct location - fibres of the cytoskeletal molecule actin (Nature, July 13, 2005).



“No one has ever shown that actin moves chromosomes,” says Dr. Jan Ellenberg, the EMBL researcher whose group carried out the research. “We were able to do so because our group is one of the few that studies cell division in starfish - an ideal model for observing division in living animal eggs.”

The starfish is an excellent model for studying oocytes, the cells that give rise to egg cells. In this marine animal, these cells are transparent and mature quickly outside the body, and can be kept alive in a drop of seawater. That’s why EMBL scientists performed some of their experiments with collaborators at the Marine Biological Laboratory in Woods Hole, MA, USA – working with animals fresh from the ocean.


Ellenberg and PhD student Péter Lénárt studied the starfish oocytes as they underwent meiosis, a special cell division that is needed to halve the number of chromosomes in an egg before it unites with a sperm. When the protective nuclear membrane surrounding the chromosomes breaks down during meiosis, it was thought that microtubules capture the chromosomes and act as ropes to pull them to the surface and expel half of them from the cell.

But when the EMBL researchers measured the microtubules, they discovered that they were, in fact, much too short to transport the chromosomes over the long distance to the surface of the large oocyte. By using a chemical to disable the microtubules, they found that cells were still able to pull chromosomes into the proper positions.

So what was moving the chromosomes?

When they repeated the experiment with a chemical that breaks down the other major type of cellular fibres, actin, the cells lost track of their chromosomes and the new cells had unequal amounts of genetic material. This condition, called aneuploidy, is thought to be a major cause of miscarriages and some types of birth defects.

Lénárt spent 18 months optimizing an imaging technology, with help from collaborators at the German Cancer Research Center (DKFZ), to visualize the delicate actin fibres before he could confirm the group’s fundamental breakthrough. He observed a network of filamentous actin forming in the region where the nuclear membrane breaks down. This network acts as a fishnet to gather all the chromosomes together and drag them close to the short microtubules. Only then, when the chromosomes are close enough, can the microtubules latch on and pull half of them outside the cell.

The implications for this pioneering work are clear. Starfish oocytes have many similarities to those of other animals, including humans. Because this mechanism is essential to prevent chromosome loss before fertilization, advances in this field could help to explain the causes of pregnancy loss and birth defects in humans.

Trista Dawson | alfa
Further information:
http://www.embl.de

More articles from Life Sciences:

nachricht A novel socio-ecological approach helps identifying suitable wolf habitats
17.02.2017 | Universität Zürich

nachricht New, ultra-flexible probes form reliable, scar-free integration with the brain
16.02.2017 | University of Texas at Austin

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Switched-on DNA

20.02.2017 | Materials Sciences

Second cause of hidden hearing loss identified

20.02.2017 | Health and Medicine

Prospect for more effective treatment of nerve pain

20.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>