1.   As cells differentiate, they repress the telomerase gene.

2.   At Geron, researcher Michael West said his company is also pursuing long-term research aimed at rejuvenating aged tissues by turning on telomerase genes.

3.   Before being injected into a patient, these specialized cells could be immortalized by adding the telomerase gene in active form.

4.   A less drastic approach might be to coax skin cells to activate their existing, but dormant, telomerase genes.

5.   All cells possess a gene, known as the telomerase gene, which can restore the telomeres to their youthful length.

6.   But in cancer cells the telomerase gene is switched on, and the cell makes genetic sequences that protect the ends of telomeres from shortening.

7.   But the telomerase gene is suppressed in most normal cells, and as people age, their telomeres decrease.

8.   DePinho and Harley said there were many other methods besides adenovirus for delivering both the telomerase gene and the telomerase protein itself.

9.   Harley and Shay have already had some success engineering viruses to carry telomerase genes, instead of harmful viral genes, into cells.

10.   Harley has been able at last to put the theory to rigorous test because of the recent discovery of the human telomerase gene.