Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Human clone not miracle cure

28.11.2001


Cloned human embryos: did genes kick in?
© SPL


Rewiring the egg: mechanism remains murky.

From a scientific viewpoint, the cloning of human embryos may be more of a step than a leap, say sceptics. If the signals that turn adult cells into embryonic ones can be found, the creation of cloned embryos for tissue repair may become redundant.

Researchers at Advanced Cell Technology (ACT) in Worcester, Massachusetts, now report that they have created cloned human embryos. They aimed to make blastocysts, hollow balls of cells from which embryonic stem cells can be isolated and used to grow immunologically matched tissues to replace diseased ones.



Other researchers question whether ACT’s short-lived embryos, which did not become blastocysts, are a success. "A critical stage of development is the kicking in of genes," explains Harry Griffin of the Roslin Institute in Edinburgh, which cloned Dolly the sheep. "They didn’t get over this threshold."

The ACT team transferred nuclei from adult skin and ovarian cells into human eggs that had been stripped of their own chromosomes. Of 19 eggs, 11 appeared to undergo early stages of embryo development by forming a ’pronucleus’, a structure which forms in eggs fertilised with sperm. Two went on to divide into 4 cells and one into 6 cells1.

Embryonic genes in the nucleus only get switched on at, or after, this stage, explains embryologist Richard Gardner of the University of Oxford, UK. Before this, embryos are instructed by molecules in the mother’s egg cell. It is unclear whether ACT’s early embryos would progress any further, says Gardner.

Damage to genes incurred during manipulation of the nucleus can halt further development, explains John Gurdon, who studies embryos at the University of Cambridge, UK. The success rate for all cloning attempts so far "is very low indeed", says Gurdon.

Many researchers are trying to uncover the underlying mechanism by which adult nuclei, which have stopped dividing, are ’reprogrammed’ - made to switch off adult genes and switch on embryonic ones. With most work being done in mice, sheep and cows, "There’s almost nothing known in humans", says Gurdon.

If such signals can be identified, they might be used directly on adult human cells, points out Griffin, to turn them into the tissue of choice. "Maybe we can miss out the first stage and reprogramme directly," he says.

This would alleviate the need for human eggs in the cloning procedure altogether. It would also avoid the risks of genetic defects in cloned tissues, which have been reported in some cloned animals.

ACT are already working on alternatives to human cloning. In the same paper they describe a technique in which they stimulated human eggs - before the stage at which they halve their number of chromosomes - to divide and form embryos without fertilization by sperm. Using a chemical that triggers ions to enter the cell, they activated 22 eggs, of which 6 went some way towards forming blastocysts.

References

  1. Cibelli, J.B. et al. Somatic cell nuclear transfer in humans: pronuclear and early embryonic development. The Journal of Regenerative Medicine, 2, 25 - 31, (2001).


HELEN PEARSON | © Nature News Service
Further information:
http://www.nature.com/nsu/011129/011129-9.html

More articles from Life Sciences:

nachricht New technique for in-cell distance determination
19.03.2019 | Universität Konstanz

nachricht Dalian Coherent Light Source reveals hydroxyl super rotors from water photochemistry
19.03.2019 | Chinese Academy of Sciences Headquarters

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Stellar cartography

The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a Zeeman- Doppler-Image of the surface of the magnetically active star II Pegasi.

A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes...

Im Focus: Heading towards a tsunami of light

Researchers at Chalmers University of Technology and the University of Gothenburg, Sweden, have proposed a way to create a completely new source of radiation. Ultra-intense light pulses consist of the motion of a single wave and can be described as a tsunami of light. The strong wave can be used to study interactions between matter and light in a unique way. Their research is now published in the scientific journal Physical Review Letters.

"This source of radiation lets us look at reality through a new angle - it is like twisting a mirror and discovering something completely different," says...

Im Focus: Revealing the secret of the vacuum for the first time

New research group at the University of Jena combines theory and experiment to demonstrate for the first time certain physical processes in a quantum vacuum

For most people, a vacuum is an empty space. Quantum physics, on the other hand, assumes that even in this lowest-energy state, particles and antiparticles...

Im Focus: Sussex scientists one step closer to a clock that could replace GPS and Galileo

Physicists in the EPic Lab at University of Sussex make crucial development in global race to develop a portable atomic clock

Scientists in the Emergent Photonics Lab (EPic Lab) at the University of Sussex have made a breakthrough to a crucial element of an atomic clock - devices...

Im Focus: Sensing shakes

A new way to sense earthquakes could help improve early warning systems

Every year earthquakes worldwide claim hundreds or even thousands of lives. Forewarning allows people to head for safety and a matter of seconds could spell...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

International Modelica Conference with 330 visitors from 21 countries at OTH Regensburg

11.03.2019 | Event News

Selection Completed: 580 Young Scientists from 88 Countries at the Lindau Nobel Laureate Meeting

01.03.2019 | Event News

LightMAT 2019 – 3rd International Conference on Light Materials – Science and Technology

28.02.2019 | Event News

 
Latest News

Levitating objects with light

19.03.2019 | Physics and Astronomy

New technique for in-cell distance determination

19.03.2019 | Life Sciences

Stellar cartography

19.03.2019 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>