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 BigH1 -- The key histone for male fertility
14.12.2017 | Institute for Research in Biomedicine (IRB Barcelona)

nachricht Guardians of the Gate
14.12.2017 | Max-Planck-Institut für Biochemie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Plasmonic biosensors enable development of new easy-to-use health tests

14.12.2017 | Health and Medicine

New type of smart windows use liquid to switch from clear to reflective

14.12.2017 | Physics and Astronomy

BigH1 -- The key histone for male fertility

14.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>