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Gene mutation linked to ALS

A collaborative nationwide effort by 32 researchers, anchored by scientists at Massachusetts General Hospital and MIT, has found an association between a gene mutation and the inherited form of amyotrophic lateral sclerosis (ALS)-Lou Gehrig's disease.

The discovery points to possible treatments that "might blunt the devastating course of this disease," the researchers said, but they cautioned that much remains to be learned.

Professor H. Robert Horvitz, Howard Hughes Medical Institute Investigator at the MIT Department of Biology, provided a cornerstone for the research, which was reported in the March 4 issue of the journal Nature.

Robert J. Brown Jr., MD, director of the Cecil B. Day Laboratory for Neuromuscular Research at Massachusetts General, the senior author of the paper, saluted his MIT colleague for his major contributions, "both intellectually and financially."

Professor Horvitz, who holds appointments at Massachusetts General in neurology and in medicine, is known internationally as an expert on the genetic analysis of development and on how genetic defects make nerve cells die.

He and Dr. Brown met in the late 1980s and found that they shared many scientific interests, including the riddle of ALS, a degenerative disorder of the nervous system. ALS is widely known as Lou Gehrig's disease for the New York Yankees first-baseman who died of it in 1941 at the age of 38. Gehrig, who was called "The Iron Man" because of his record of playing in 2,130 consecutive games, was forced to the bench by a mysterious erosion of his physical skills that was diagnosed as ALS.

The famous British astrophysicist Stephen Hawking suffers from ALS. His case is considered atypical because he has survived for more than two decades. Usually the disease is fatal in about five years.

As a result of their shared interests, Professor Horvitz and Dr. Brown helped arrange a workshop, held near Chicago in 1988, that brought together a pool of researchers and resources to attack the problem of ALS. The study published in Nature is one of the fruits of that collaboration.

The devastation of ALS begins when nerves in the brain and spinal cord begin to degenerate. The current research focused on one of the two versions of ALS, familial or inherited ALS (FALS), which accounts for about 10 percent of the known cases. Most cases are classified as sporadic or spontaneous ALS. The two types of the disease, however, are clinically similar, which leads to the hope that treatments being developed for FALS will be of help in non-familial ALS.

The latest work reports a "tight genetic linkage" between FALS and a gene that encodes the enzyme superoxide dismutase (SOD1). The enzyme protects the body by neutralizing free radicals, byproducts of normal metabolism, which if unchecked can destroy cells.

The researchers identified 11 gene changes in 13 FALS families. The changes were not found in more than 100 chromosomes from normal individuals, the researchers wrote.

"Although it is conceivable that the mutation that causes FALS leads to the accumulation of mutations in other genes, including SOD1, this possibility seems unlikely."

While there is now great promise for a treatment that may successfully attack the disease, Professor Horvitz cautioned against over-optimism.

"There is much that is not known," he stressed at a news conference at the Massachusetts General research center in Charlestown on March 3, giving several examples:

Is the gene mutation that has been found causal, that is, does it cause the disease? If it is causal, how does it cause the disease? What does the gene mutation do to the enzyme superoxide dismutase (SOD1), an important metabolic regulator of cells? Does the mutation impair the enzyme, or might it enhance its performance?

Research is under way to seek answers to those and other questions, he said.

Professor Horvitz, 45, is noted for his work in deepening the understanding of the genetic analysis of the development of cell lineages. He has made a close study of the nematode, a microscopic worm about a millimeter long, that lives in the soil. Caenorhabditis elegans, as scientists know the worm, is the only animal for which science has been able to develop a complete map of its cells and a complete wiring diagram of its nervous system. Professor Horvitz has studied how cells develop in the nematode. Research has shown that genes controlling nematode development are strikingly similar to genes in other animals, including humans.

Professor Horvitz received bachelor degrees in mathematics and economics from MIT (1968) and the master's degree (1972) and PhD (1974) in biology from Harvard University. He joined the faculty of MIT in 1978.

A version of this article appeared in the March 10, 1993 issue of MIT Tech Talk (Volume 37, Number 25).

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