Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Cells reprogram in 24 hours

19.04.2002


Erasing molecular memory of parents could shed light on clones.

Cells naturally wipe out the mark of their parents in 24 hours, say cloning experts. Exactly how may begin to explain the way that animal clones and stem cells are reprogrammed. Not all genes are born equal. In mammals, some genes are imprinted - cells switch on only the copy inherited from mum or dad, not both. This sex stamp must be erased and rewritten in sperm and egg cells, however, so they are correctly labelled as male or female when they fuse to form the next generation.

The deletion occurs in as little as a day, Fumitoshi Ishino of the Tokyo Institute of Technology in Yokohama, Japan, and his team have now shown. Even as an embryo is growing, the cells destined to form its ovaries and testes are scrubbing out established patterns of gene activity1.



The finding begins to unravel how cells overwrite their history, explains Azim Surani of the Wellcome/CRC Institute in Cambridge, UK. This is something researchers working on cloning and stem cells long to find out. "Any information we get is bound to be helpful," says Surani.

Programming skills

Hours after fertilisation sperm and egg overwrite their DNA with instructions for making an embryo - imprints remain intact. Cloned mammals are thought to die early or suffer ill health partly because this reprogramming is incomplete; in clones made from some cell types, imprinting is upset as a result.

Some of the cell machinery that erases imprints may also do reprogramming, says Wolf Reik, who studies these phenomena at the Babraham Institute in Cambridge, UK. "I’m sure there are going to be parallels."

Once found, the molecules involved might be harnessed to improve the efficiency of cloning. Similarly, adult stem cells might be better persuaded to rewrite their normal instructions and generate unusual cell types.

But cloning researcher Rudolf Jaenisch of the Whitehead Institute in Cambridge, Massachusetts, is not convinced that the two processes - removing imprinting and reprogramming - are comparable. He says that cloning shortcuts the natural process.

Wipe out

Ishino’s team believe that, under the right conditions, the imprint on a donor cell’s DNA is carried unaffected into the clone. They used this to test when nuclear imprinting is erased in a growing embryo.

The group made clones from the cells in mice embryos that give rise to ovary and testes. They took the cells at different stages of embryo development. Cells taken after imprinting had been erased gave rise to clones that died very young, they found. Clones from cells that still had some imprinting lasted longer.

Midway through an embryo’s growth, genes lose their sex bias and switch into a default state in a day, the researchers conclude. Chemical gags are removed from genes one by one, to make the activity of both copies equal. The speed suggests that the imprinting pattern is actively wiped out, says Reik, rather than being lost passively over many cell divisions.

The experiments also add to growing evidence that embryos cannot survive without correct imprinting. "Clones that have no parental information do not develop to term," says Ishino. Similarly, embryos carrying two copies of either the mother or father’s genes cannot survive.

References
  1. Lee, J. Erasing genomic impinting memory in mouse clone embryos produced from day 11.5 primordial germ cells. Development, 129, 1807 - 1817, (2002).


HELEN PEARSON | © Nature News Service

More articles from Life Sciences:

nachricht Could this protein protect people against coronary artery disease?
17.11.2017 | University of North Carolina Health Care

nachricht Microbial resident enables beetles to feed on a leafy diet
17.11.2017 | Max-Planck-Institut für chemische Ökologie

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 “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>