Cedars-Sinai Scientists Localize New Ataxia/Epilepsy Gene

Five spinocerebellar ataxia (SCA) genes had been previously identified by various research groups, including SCA2, which, like SCA10, was found by the Cedars-Sinai team of Stefan-M. Pulst, M.D. Like SCA2, SCA 10 shows anticipation, a phenomenon whereby onset of the disease is earlier and earlier with each successive generation. The presence of anticipation may provide an important clue for the isolation of the gene, since it may indicate that the genetic defect is caused by unstable DNA repeats.

In contrast to other inherited ataxias, however, 20 percent of members of the family affected by the ataxia suffered seizures. "This connection makes isolation of the genetic defect so exciting", says Dr. Pulst, "because it will likely shed light on the much more common epilepsies."

It was approximately a year ago that the Pulst team identified the Mexican-American family exhibiting the rare form of ataxia. They have now been able to localize the SCA10 gene on the long arm of chromosome 22 by conducting a search that included some 300 genetic markers covering the entire human genome. It was the 40th of these that suggested the researchers were in the right region. Interestingly, the new gene is not close either to other ataxia genes, or to any for epilepsy.

Whereas it took the team 5 years to identify the prior ataxia gene, they expect to identify SCA10 as soon as two years from now, thanks to advances in the Human Genome Project. Dr. Pulst is director of the Cedars-Sinai Division of Neurology since 1993 and became holder of the Carmen and Louis Warschaw Chair in Neurology in 1991. He is also director of the Cedars-Sinai Neurogenetics Laboratory, scientific director of the Parkinson's Disease Research and Treatment Center at the Medical Center, and a professor of medicine at UCLA.

Key contributors include first author Lan Zu, PhD, a fellow, and Karla Figueroa, a research associate, in the Rose Moss Laboratory for Parkinson's and Neurodegenerative Diseases of the Burns & Allen Research Institute at Cedars-Sinai Medical Center, and Raji Grewal, MD, a member of the Department of Neurology at the USC School of Medicine.

The study was supported by grants from the National Institute of Neurological Diseases and Stroke, the Joseph Drown Foundation, and the Carmen and Louis Warschaw Endowment for Neurology.