Long-term benefits from a ‘moment of silence’
By temporarily silencing a hyperactive gene, scientists dramatically boost the efficiency of mouse cloning
In principle, somatic cell nuclear transfer (SCNT) is a potent tool for scientists looking to produce exact genetic replicas of a particular animal. By injecting a nucleus from an adult cell into an oocyte from which the nucleus has been removed, one can initiate the embryonic development process and derive a clone of the ‘donor’ animal.
Unfortunately, this technique is terribly inefficient, with a success rate of 1–2% in mice. “This must be due to some errors in the reprogramming of the donor genome into the ‘totipotent’ state, which is equivalent to the state observed in conventionally fertilized embryos,” explains Atsuo Ogura of the RIKEN BioResource Center in Tsukuba. However, Ogura and colleagues have now made significant progress in clearing a major roadblock thwarting SCNT success.
During development of female mammalian embryos, one of the two X chromosomes is targeted for inactivation, thereby ensuring that both males and females achieve equivalent expression of X-linked genes. This inactivation depends on RNA produced by the Xist gene, which blankets the selected chromosome and sets the inactivation process in motion.
Ogura and his team previously determined that Xist is inappropriately activated in SCNT embryos, impairing expression of essential genes, and have now set about correcting this defect. Irreversibly inactivating this gene is not an option, so the researchers injected molecules called ‘short interfering RNAs’ (siRNAs) that directly inhibited Xist activity in early stage male SCNT embryos, which must maintain their single X chromosome in order to survive.
This treatment markedly boosted expression of X chromosomal genes relative to untreated controls, and although the direct effects of siRNA injection were fleeting, the benefits lingered. “The siRNA was effective for only 72 hours,” says Ogura, “but it had long-term effects not only on the birth rate but also on the health status of the offspring.” Indeed, his team achieved a success rate of nearly 20%—ten-fold better than previous efforts—and generated mouse pups that were apparently normal and healthy.
The implications for this improved efficiency extend beyond mass-produced mice, and this approach could represent a step toward improving the economics of cloning other species such as pigs and sheep, which are harder to genetically manipulate but nevertheless of considerable agricultural and scientific interest. “Our goal is to increase the birth rate of healthy cloned offspring not only in mice but also other mammals,” says Ogura, “and to understand the mechanisms by which the genome is drastically altered during the life cycle.”
The corresponding author for this highlight is based at the Bioresource Engineering Division, RIKEN BioResource Center
gro-pr | Research asia research news
The most recent press releases about innovation >>>
Die letzten 5 Focus-News des innovations-reports im Überblick:
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
Nano-hologram paves way for integration of 3-D holography into everyday electronics
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.
In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...
Biofilms: Researchers find the causes of water-repelling properties
Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...
For the first time, scientists have succeeded in studying the strength of hydrogen bonds in a single molecule using an atomic force microscope. Researchers from the University of Basel’s Swiss Nanoscience Institute network have reported the results in the journal Science Advances.
Hydrogen is the most common element in the universe and is an integral part of almost all organic compounds. Molecules and sections of macromolecules are...