A Johns Hopkins geneticist has discovered a critical link between the health of stem cells and the length of the chromosome ends within them.

Chromosome ends, or telomeres, are repetitive stretches of DNA that protect chromosomes in much the same way as plastic shoelace tips prevent the fabric from fraying. Each time a cell divides, its chromosome ends get a little shorter, and, eventually, the cell can no longer divide because its critical genetic information is exposed.

In stem cells, however, a protein called telomerase normally maintains the telomeres’ length, allowing the cells to divide indefinitely.

Now, the Hopkins researchers report mice engineered to have just half the normal amount of telomerase can’t maintain their stem cells’ chromosome ends, proving a little telomerase isn’t enough.

In addition, offspring of such mice bred to have normal levels of telomerase still exhibited early loss of stem cells.

These offspring have what we have called ‘occult’ genetic disease — their genetic make-up is perfectly normal, but they still have the physical problems of their parents, said Carol Greider, professor of molecular biology and genetics. This phenomenon could complicate the hunt for disease genes.

More here.