SYDNEY, Australia -- Researchers at the Children's Medical Research Institute in Sydney have discovered a whole new level of complexity in the actions of genes in cells.

By studying the action of genes in the muscle tissue of transgenic mice, the researchers, led by Edna Hardeman, have discovered that genes can "flash" on and off, apparently at random. During extensive testing of the proteins being produced by cells in the mouse muscle tissue, they realized that the genes in each cell were acting differently. The discovery, detailed in the December issue of the international journal Genes and Development, has considerable significance for monitoring the results of therapies and potentially for gene therapy.

Hardeman said the conventional wisdom has been that when "a gene is switched on in a tissue, it's on for life." She said she believes there is an unknown signaling mechanism -- probably a hormone in the blood -- that turns the genes on and off as a means of regulating the production of protein.

In other words, the mechanism ensures that the body produces the right amount of a particular protein.

Hardeman said the discovery has created considerable interest among other scientists, since it adds "another level of complexity no one knew was there." She said the discovery may change the way doctors monitor the effectiveness of certain treatments, since it shows that tests done at different times may give different results. It also may be possible to alter the switching process, but first the switch must be found. Hardeman's team is now looking for the signaling protein. *