Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Regulating human X chromosomes doesn’t use same gene as in mouse

01.08.2002


A gene thought to keep a single X chromosome turned on in mice plays no such role in humans, Johns Hopkins researchers report in the August issue of the American Journal of Human Genetics.



The finding is likely to relegate the disproven gene to relative obscurity, at least in humans, says Barbara Migeon, M.D., of the McKusick-Nathans Institute of Genetic Medicine, whose laboratory found the human version of the gene in 2001. It also moves the search for the gene from the X chromosome to the 22 other types of chromosomes found in human cells, she adds.

In mammals, one of the two X chromosomes inherited by all females is turned off during development to prevent a dangerous double dose of proteins. A gene called Xist unquestionably turns off X chromosomes in mice, humans and other mammals. Because every cell needs one active X chromosome, Xist must be suppressed on one X in both females and males (which have an X and a Y chromosome). Which gene (or genes) does this is still in question, says Migeon.


In mice, researchers elsewhere pointed to the Tsix gene, because it suppressed Xist and was itself expressed only on the active X. However, studying cells from various human developmental stages, Migeon and her team discovered that human Tsix is expressed only on the inactive X chromosome, right alongside Xist. The two continue to be expressed together until after birth, when for reasons unknown Tsix gradually disappears.

"The difference is striking," says Migeon, also a professor of pediatrics. "In mice, researchers have suggested that Tsix was the gene in mammals that suppresses Xist and allows an X chromosome to remain active, but we’ve shown clearly that it does not do this in humans."

Migeon suggests instead that the mouse Tsix is involved in imprinting, a way cells determine which of two gene copies to use to make proteins that depends only on which parent the copy came from. In mice, X-inactivation in the placenta is imprinted -- the X from the mother is always "on." In other embryonic tissues, however, inactivation occurs randomly -- the X from either the mother or father could be on. In humans, X-inactivation is random for all tissues, including the placenta.

"Human and mouse Tsix are very different from one another," says Migeon. "Sequence differences and missing regions in human Tsix are a window on what’s happening in the mouse and help explain why the gene doesn’t have the same function in humans."

Much remains unknown about human Tsix, including what, if anything, it does in humans. However, Migeon will leave those mysteries for others to investigate, choosing instead to continue a 30-year quest to fully understand X-inactivation in human development.

"We expect to find a gene on one of the other chromosomes that turns off Xist in a random fashion," says Migeon. "It is difficult to envision how a gene on the X chromosome could, by itself, regulate the function of Xist on only one member of the X chromosome pair."

To track down Xist’s true suppressor, Migeon and her colleagues are studying human cells with "trisomies" -- cells that have 23 pairs of chromosomes plus a third copy of one chromosome. In these cells, if the Xist-suppressing gene is on the chromosome with three copies, X-inactivation would be abnormal, Migeon says.


The studies were funded by the National Institutes of Health. Authors on the study are Migeon, Catherine Lee, Ashis Chowdhury and Heather Carpenter, all of Johns Hopkins.

Joanna Downer | EurekAlert!
Further information:
http://www.journals.uchicago.edu/AJHG/journal/issues/v71n2/024004/024004.web.pdf
http://www.hopkinsmedicine.org

More articles from Life Sciences:

nachricht Transport of molecular motors into cilia
28.03.2017 | Aarhus University

nachricht Asian dust providing key nutrients for California's giant sequoias
28.03.2017 | University of California - Riverside

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

Transport of molecular motors into cilia

28.03.2017 | Life Sciences

A novel hybrid UAV that may change the way people operate drones

28.03.2017 | Information Technology

NASA spacecraft investigate clues in radiation belts

28.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>