Huntington's disease strikes mice.

Huntington's disease, a fatal neurodegenerative disorder, stems from an unusual mutation in which a gene becomes too big for its own good. In people with the disease, a small bit of the gene's DNA sequence repeats an abnormally large number of times (SN: 6/10/95, p. 360). Following the mutant gene's instructions, cells create a protein that has extra amino acids.

A collaboration of scientists from the United Kingdom and Germany has now raised mice whose genomes include a small portion of the repeat-laden human Huntington disease gene. As they age, the mice begin to suffer symptoms of Huntington's disease, including tremors, epileptic seizures, and neurodegeneration. "Their brains are 20 to 30 percent smaller than [the brains of] their normal siblings," says Gillian P. Bates of Guy's Hospital in London, who headed the research effort.

Bates suggests that the mice will help investigators unravel the mystery of how the mutant proteins cause Huntington's disease. "It's beautiful, very important work. The mice show the classic signs of the disease," says Richard Myers of Stanford University, who has recently added a much larger portion of the disease gene to mice. Myers and his colleagues are still waiting to see if their mice exhibit symptoms.