From the Labs: Biomedicine
Mice from Skin Cells
Reprogrammed cells develop into live animals.
Source: “iPS cells produce viable mice through tetraploid complementation”
Qi Zhou et al.
Nature 461: 86-90
“iPS cells can support full-term development of tetraploid blastocyst-complemented embryos”
Shaorong Gao et al.
Cell Stem Cell 5: 135-138
Results: Researchers in China grew viable mice from induced pluripotent stem cells, which are made by modifying adult cells. Some of the mice went on to produce a second generation of offspring.
Why it matters: The research proved that induced pluripotent stem (iPS) cells, like embryonic stem cells, can differentiate into any cell type in the body. It suggests that iPS cells can be used for the same scientific purposes as embryonic stem cells–for example, to develop treatments that replace diseased cells.
Methods: Researchers transferred iPS cells generated from mouse fibroblasts (a type of skin cell) into specialized embryos that lacked the ability to develop on their own. Introducing the iPS cells triggered the embryos to begin developing. The embryos were then transplanted into surrogate mothers.
Next steps: Although the scientists’ achievement was impressive, only 1 to 3 percent of the embryos developed into live mice. In addition, many of those mice had physical abnormalities or died soon after birth. Scientists want to understand how the differences between iPS cells and embryonic stem cells might lead to these abnormalities. They also want to increase the rate of live births.
A machine rapidly modifies bacterial genomes.
Source: “Programming cells by multiplex genome engineering and accelerated evolution”
Harris H. Wang, Farren J. Isaacs, et al.
Nature 460: 894-898
Results: A machine developed by researchers at Harvard, MIT, and Georgia Tech can quickly make thousands of targeted changes to a bacterial genome. Using the machine to modify E. coli bacteria that produce lycopene, an antioxidant found in tomatoes, the researchers took just three days to create a strain that produced five times as much of the chemical as the original.
Why it matters: The machine could dramatically speed the increasingly sophisticated process by which researchers modify microbes to produce biofuels and other useful chemicals. This type of engineering is slow because the scientists typically need to change many interrelated genes, but they can make at most a few changes to the bacterial genome at a time. Automating the process can accomplish in just a few days work that previously would have taken weeks or months.
Methods: Scientists mix bacteria with more than 23,000 different short strands of DNA, each of which could modify one of 24 different genes in a way that could enhance the organisms’ ability to perform a certain task. One altered strand, for example, might make an enzyme more efficient. The new machine subjects vials of the mixture to temperature and chemical cycles that encourage the bacterial cells to take up the foreign DNA, swapping a particular strand into their genomes in place of the native piece it resembles. Within
a vial, the rapidly reproducing bacteria take up more of the foreign DNA in each generation. The researchers examine the simultaneously produced strains and pick the one whose genetic changes make it most efficient at the desired task.
Next steps: Researchers want to improve the efficiency of the device, increasing the proportion of bacterial cells that end up with large numbers of genetic changes. They also plan to extend the technology to human cell lines and to yeast, which is important for making biofuels.
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