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 Cancer diagnosis: no more needles?
25.05.2018 | Christian-Albrechts-Universität zu Kiel

nachricht Less is more? Gene switch for healthy aging found
25.05.2018 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>