Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

How can identical twins be genetically different?

27.07.2006
U-M scientists find new genes linked to rheumatoid arthritis that are expressed differently in genetically identical twins

They sleep together, eat together, and most people find it impossible to tell them apart. Identical twins who grow up together share just about everything, including their genes. But sometimes only one twin will have health problems when genetics predicts both of them should.

Scientists at the University of Michigan Medical School are just beginning to understand how two people who are so similar biologically can be so different when it comes to the development of diseases like rheumatoid arthritis.

U-M researchers have discovered three genes that are over-expressed in rheumatoid arthritis, or RA, that were not known to be associated with the disease before. They also found that non-genetic factors influenced the expression of these genes and that the expression patterns varied between identical twins where only one twin had RA. Results of the U-M study were published in the July issue of Arthritis and Rheumatism.

RA is a chronic inflammatory disease that damages joints. RA causes pain, loss of movement, and bone deformities. It affects 2.1 million Americans. There are many genetic factors that put people at a high-risk for developing RA, yet only 15 percent of identical twins will both develop it.

Scientists compared gene expression patterns of 11 pairs of monozygotic twins, who shared the same egg and were genetically identical, but only one of them had RA. They found three new genes that were significantly over-expressed in the twin with RA compared to the one without the disease. This is the first report for RA that examines gene expression patterns in monozygotic twins.

"This is the crux of the issue we are trying to address in RA -- how two patients can have the same genes but different disease outcomes. Identical twins represent the best experimental system to address this question," says Joseph Holoshitz, M.D., an associate professor of internal medicine at U-M Medical School and co-author of the study.

The advantage of studying twins is that they start out with the exact same genetic information. Therefore, differences in gene expression are attributable to different environmental factors rather than genetics. Such factors could cause a random genetic mutation or affects how DNA is packaged.

"There's a lot of variability in the severity of the disease, symptoms, and the response a patient will have to treatment. Differences in the expression of genes caused by environmental factors that modify DNA have a lot to do with this variability," says Holoshitz.

The most significantly over-expressed of the three genes codes for a protein called laeverin. This is an enzyme that destroys certain types of proteins. Scientists hypothesize that laeverin promotes the tissue damage of the joint found in RA by degrading cartilage and bone.

Another previously unidentified gene codes for a protein called 11â-HSD2 that helps deactivate the hormone cortisol. This hormone is involved in the response to stress and also has anti-inflammatory effects. The discovery that 11â-HSD2 is over-expressed in patients may explain a common characteristic of RA patients.

"It has been known for a long time that there is a deficiency of cortisol in RA patients," says Holoshitz.

The third gene U-M scientists discovered codes for Cyr61, which plays a role in angiogenesis, a process that recruits new blood vessels to an area.

In the early stages of RA, the tissue in the joint begins to grow and divide similarly to a benign tumor. The growing mass, which secretes proteins that degrade tissue, uses angiogenesis to recruit new blood vessels to supply it with nutrients. The angiogenic factor Cyr61 could be involved with this process.

"This paper describes only a glimpse of what this approach might reveal. There are many other categories of genes where expression varies between twins. We are just beginning to understand how RA is able to affect people in different ways. The newly discovered genes provide important insights into the nature of the disease and facilitate the design of novel treatment strategies for RA," says Holoshitz.

Rossitza Iordanova | EurekAlert!
Further information:
http://www.med.umich.edu

More articles from Life Sciences:

nachricht Unique genome architectures after fertilisation in single-cell embryos
30.03.2017 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH

nachricht Transport of molecular motors into cilia
28.03.2017 | Aarhus University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

NASA laser communications to provide Orion faster connections

30.03.2017 | Physics and Astronomy

Reusable carbon nanotubes could be the water filter of the future, says RIT study

30.03.2017 | Studies and Analyses

Unique genome architectures after fertilisation in single-cell embryos

30.03.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>