Stem cell efforts take steps
Resetting no longer requires DNA-altering viruses
After the landmark achievement in late 2007 of reverting human adult skin cells to an embryonic stem cell–like state — a technique that does not involve creating or destroying human embryos — stem cell researchers have a new focus. In 2008 they worked on improvements to this technique that could make the cells safe for medical therapies.
One major step was eliminating the DNA-altering viruses that deliver the reprogramming genes into the skin cells. These viruses pose a cancer risk, in part, because they insert the reprogramming genes at random places in the cells’ DNA. But Matthias Stadtfeld, a molecular biologist at Massachusetts General Hospital in Boston, and his colleagues created embryonic-like stem cells from mouse skin cells using a different kind of virus that does not alter the cells’ DNA (SN: 10/25/08, p. 8). “None of the cells that we produced had any evidence of any virus left” after reprogramming, Stadtfeld says.
Another challenge was confirming whether such reprogrammed cells have all the genetic traits of true embryonic stem cells. Jeanne Loring of The Scripps Research Institute in La Jolla, Calif., and her colleagues did that when they found that 299 interacting genes essential to an embryonic stem cell’s special abilities had similar activity in reprogrammed skin cells (SN Online: 8/24/08), (SN: 9/13/08, p. 17).
Making the human The human version of a stretch of DNA responsible for turning genes on and off spurs development in mouse limbs, but the same stretch of DNA from chimps does not. The difference points to a genetic change that may be crucial in setting humans apart from other primates (SN: 9/27/08, p. 13).
Do-it-yourself DNA Making a complete microbial genome from scratch by assembling the individual letters of its genetic code paves the way for making synthetic microbes (SN: 1/26/08, p. 52).
Reviving extinct DNA Scientists insert a bit of DNA from the extinct Tasmanian tiger into a mouse embryo (below). The DNA turns on a gene in the mouse’s cartilage-producing cells (SN: 6/7/08, p. 9).
Energizer mouse Two drugs, one that stimulates a gene and another that targets a protein, can boost the running endurance of mice by about 75 percent and 45 percent (SN: 8/30/08, p. 14).
Ch-ch-ch-changes Chemical tags that affect gene activity change over a person’s lifetime, and the changes follow similar patterns among family members (SN: 7/19/08, p. 9).
Common age Research on aging finds yeast and roundworms share 25 longevity-related genes; humans have 15 of these genes (SN: 3/15/08, p. 164).
Community of one Scientists discover a single bacterial species, Candidatus Desulforudis audaxviator (shown above),living deep in a gold mine in South Africa. Its genome contains everything it needs to live independently (SN: 11/8/08, p. 20).
Stem cell snag In a possible setback for scientists developing stem cell therapies for Parkinson’s disease, researchers find that some nerve cells transplanted into the brains of Parkinson’s patients show signs of getting the disease as many as 16 years after the transplant (SN: 4/12/08, p. 229).