Biologists have developed an efficient way to genetically modify human embryonic stem cells. Their approach, which uses bacterial artificial chromosomes to swap in defective copies of genes, will make possible the rapid development of stem cell lines that can both serve as models for human genetic diseases and as testbeds on which to screen potential treatments, they say.
"This will help to open up the whole human embryonic stem cell field. Otherwise, there's really few efficient ways you can study genetics with them," said Yang Xu, professor of biology at the University of California, San Diego who directed the research. Xu and co-authors Hoseok Song and Sun-Ku Chung, both postdoctoral fellows in Xu's research group, describe their technique in the January 8 issue of the journal Cell Stem Cell.
Most attempts to alter the genetic makeup of the cells have proved too inefficient, Xu said. His group used bacterial artificial chromosomes, or BACs, to improve the yield.
BACs are synthesized circles of human DNA, which bacteria will replicate just like their own native chromosomes. Commercially available BACs can be modified within bacterial cells to insert altered copies of specific genes. Once the modified BACs are introduced into human cells, they will sometimes pair up with a matching segment of a human chromosome and swap segments of DNA, a process called homologous recombination.
The advantage of using BACS to alter the genetic code in human cells comes from the long flanking sequences on either side of the modified gene, which increases the chance that the BAC with line up with native DNA in position for a swap. Other genetic approaches have been limited by shorter segments of DNA.
Using BACs, the team was able to substitute modified genes in 20 percent of treated cells. Standard methods of genetic modification typically achieve modification in fewer than one percent of cells, Xu said.
His group s
|Contact: Yang Xu|
University of California - San Diego