Salk Institute Discovery a Key to Leukemia Testing : Genetics: Identification of the gene that triggers the disease is likely to lead to screening procedure.

Salk Institute scientists have uncovered a gene that triggers certain forms of leukemia, a discovery that may lead to the development of a screening test within the next few months, they announced today.

Armed with these results, researchers can now study how this particular gene functions, and may eventually find more effective treatments for types of leukemia that predominantly occur among children.

“A new leukemia gene is--without question--an important discovery,” said Ray White, co-chairman of the department of human genetics at the University of Utah.

The finding represents one of the first medically significant genes to be uncovered as a direct result of an international project to decipher the genetic blueprint of humans.

“Once you recognize or understand the gene and know where it is, that could lead to techniques for making genetic modifications,” said Theodore Friedmann, professor of pediatrics at UC San Diego and a pioneer in the field. “It’s certainly going to lead to treatments.”

The new gene, whose discovery is reported today in Nature Genetics magazine, was ferreted out by Dr. Glen Evans, associate professor of molecular genetics at the Salk Institute and an author of the study. The gene is thought to contribute to acute lymphocytic and myelocytic leukemias, cancers of white blood cells that occur most often in children.

The research was part of the Human Genome Project, in which scientists hope to create a genetic map to find and repair faulty genes that cause as many as 4,000 diseases, such as cancer, diabetes, Huntington’s and Alzheimer’s. The blueprint, once likened to the quest for the “Holy Grail” of genetics, now seems attainable, scientists say.

For the last three years, Evans and his colleagues have been mapping human chromosome 11--one of the 23 pairs of chromosomes that make up the human genetic blueprint. This chromosome contains about 4,500 genes and is known to cause 150 diseases. He focused on the chromosome after a classmate of his 12-year-old daughter developed acute lymphocytic leukemia.

Scientists had already noticed that a characteristic of leukemia is a break in chromosomes. Evans speculated that a gene in the broken segment might indeed be responsible for the uncontrolled growth of cancer cells.

His suspicion turned out to be on target: The gene he discovered in the broken region of chromosome 11 turned out to be a close relative of a gene that had already been identified as critical to growth in a fruit fly.

Knowing what the gene does in a fruit fly allowed Evans to crack the code and figure out its role in humans. This newly discovered gene orchestrates the activity of other genes.

“In flies, it’s a master control gene,” Evans said. “The interruption of this key gene in white blood cells undoubtedly disrupts gene activity that normally allows the cell to mature. As a result we get endless proliferation of immature cells.

“Finding out how how these leukemia cells start may help us invent ways to halt them. I suspect that the same gene is probably also involved in other types of leukemia.”

Evans estimated that with the knowledge of the gene, and its DNA sequence, an experimental diagnostic test could be developed in two months.

He and others agreed that cracking the DNA code with one gene allows scientists to move forward to decipher others.

“It’s as though we understand the alphabet but not the language, and in this case we understand the alphabet and some of the words,” he said.

“It’s the difference between having your car break down in the desert and having a philosophical treatise on principles of combustion or having a repair manual,” White said. “Which would you rather have?”

Researchers conceded, however, that the gene discovery would not instantly lead to better therapies, because treatments will take longer to develop than screening tests.

“It’s still very early to tell how significant an effect this is going to have on treatments or cures,” said John Wasmuth, professor of biological chemistry at UC Irvine. “(But) it certainly does make a very accurate diagnostic test possible.”