The development of the mouse, reported in the July 18, 2002 issue of the journal Neuron, provides a springboard into the study of Rett syndrome, the leading cause of mental retardation in girls.
First recognized as a syndrome in the 1980s, the disorder affects one in 10,000-15,000 girls. It is particularly devastating for families with affected children because infants are seemingly normal at birth and achieve the usual developmental milestones for the first few months of life. Then, as the infant reaches toddlerhood, a sudden and dramatic decline in physical and mental capabilities takes hold, accompanied by onset of seizures, irregular breathing, awkward gait, and hand-wringing.
"I know of no other neurological disease that gives this distinctive stereotypic behavior -- this hand-wringing these girls do basically all the time they are awake," said Zoghbi. "With this mouse model we can now ask, 'Why is that?'"
Zoghbi has been studying Rett syndrome since the mid-1980s, when she first encountered patients with the disorder as a neurology fellow and decided to search for the gene responsible for the disorder. She reasoned that the gene must be on the X chromosome, the female sex chromosome, and it must also be essential because there had been no males reported to have the syndrome. (Since males have only one X chromosome, mutations that knock out the gene's function could be lethal at an embryonic stage.) In females, there are two copies of the X chromosome, but in each cell only one of the two X chromosomes is
Contact: Jim Keeley
Howard Hughes Medical Institute