Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Pairing up: How chromosomes find each other

02.11.2011
After more than a century of study, mysteries still remain about the process of meiosis—a special type of cell division that helps insure genetic diversity in sexually-reproducing organisms. Now, researchers at Stowers Institute for Medical Research shed light on an early and critical step in meiosis.

The research, to be published in the Nov. 8, 2011 issue of Current Biology, clarifies the role of key chromosomal regions called centromeres in the formation of a structure known as the synaptonemal complex (SC). "Understanding this and other mechanisms involved in meiosis is important because of the crucial role meiosis plays in normal reproduction—and the dire consequences of meiosis gone awry," says R. Scott Hawley, Ph.D., who led the research at Stowers.

"Failure of the meiotic division is probably the most common cause of spontaneous abortion and causes a number of birth defects such Down syndrome," Hawley says.

Meiosis reduces the number of chromosomes carried by an individual's regular cells by half, allocating precisely one copy of each chromosome to each egg or sperm cell and thus ensuring that the proper number of chromosomes is passed from parent to offspring. And because chromosomes come in pairs—23 sets in humans—the chromosomes must be properly matched up before they can be divvied up.

"Chromosome 1 from your dad has to be paired with chromosome 1 from your mom, chromosome 2 from your dad with chromosome 2 from your mom, and so on," Hawley explains, "and that's a real trick. There's no room for error; the first step of pairing is the most critical part of the meiotic process. You get that part wrong, and everything else is going to fail."

The task is something like trying to find your mate in a big box store. It helps if you remember what they are wearing and what parts of the store they usually frequent (for example, movies or big-screen TVs). Similarly, chromosomes can pair up more easily if they're able to recognize their partners and find them at a specific place.

"Once they've identified each other at some place, they'll begin the process we call synapsis, which involves building this beautiful structure—the synaptonemal complex—and using it to form an intimate association that runs the entire length of each pair of chromosomes," Hawley explains.

Some model organisms employed in the study of meiosis, such as yeast and the roundworm Caenorhabditis elegans, use the ends of their chromosomes to facilitate the process. "These organisms gather all the chromosome ends against the nuclear envelope into one big cluster called a bouquet or into a bunch of smaller clusters called aggregates, and this brings the chromosome ends into proximity with each other," Hawley says. "This changes the problem of finding your homologue in this great big nucleus into one of finding your mate on just the surface of the inside of the nucleus."

But the fruit fly Drosophila melanogaster—the model organism in which meiosis has been thoroughly studied for more than a century, and which Hawley has studied for almost 40 years – has unusual chromosome ends that don't lend themselves to the same kind of clustering.

"So even though the study of meiosis began in Drosophila, we really haven't had any idea how chromosomes initiate synapsis in Drosophila," Hawley says. "Now, we show that instead of clustering their chromosome ends, flies cluster their centromeres—highly organized structures that chromosomes use to move during cell division. From there, the biology works pretty much as you would expect: synapsis is initiated at the centromeres, and it appears to spread out along the arms of the chromosomes."

The ramifications of the findings extend beyond fruit flies, as there's some evidence that synapsis starts at centromeres in other organisms. In addition, Hawley and coauthors found that centromere clustering may play a role later in meiosis, when chromosomes separate from their partners.

"There's reason to believe that some parts of that process will be at least explorable and potentially applicable to humans," Hawley said.

The work also is notable as an example of discovery-based science, Hawley said. "We didn't actually set out to study the initiation of meiosis; we were simply interested in characterizing the basic biology of early meiosis."

But postdoctoral researcher and first author Satomi Takeo, Ph.D., noticed that centromere clustering and synaptonemal complex initiation occurred in concert, and her continued observations revealed the role of centromeres in initiating synapsis.

"I was staring with tired eyes at the cells that I was analyzing," Takeo recalls. "Somehow I started looking at the spots I had previously ignored—probably because I thought they were just background noise—until I saw the connection between centromere clustering and synapsis initiation. After going through many images, I wrote an email to Scott, saying, 'This is really important, isn't it??' With that finding, everything else started to make sense."

In addition to Hawley and Takeo, the paper's authors include Cathleen M. Lake at the Stowers Institute for Medical Research and Eurico Morais-de-Sá and Cláudio D. Sunkel at Universidade do Porto in Porto, Portugal, who provided information on the earliest stages of the process.

About the Stowers Institute for Medical Research

The Stowers Institute for Medical Research is a non-profit, basic biomedical research organization dedicated to improving human health by studying the fundamental processes of life. Jim Stowers, founder of American Century Investments, and his wife Virginia opened the Institute in 2000. Since then, the Institute has spent over 800 million dollars in pursuit of its mission.

Currently the Institute is home to nearly 500 researchers and support personnel; over 20 independent research programs; and more than a dozen technology development and core facilities. Learn more about the Institute at www.stowers.org.

Gina Kirchweger | EurekAlert!
Further information:
http://www.stowers.org

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

DGIST develops 20 times faster biosensor

24.04.2017 | Physics and Astronomy

Nanoimprinted hyperlens array: Paving the way for practical super-resolution imaging

24.04.2017 | Materials Sciences

Atomic-level motion may drive bacteria's ability to evade immune system defenses

24.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>