The same compounds some plants like periwinkle use to fight off fungus may one day treat a form of mental retardation.
The most common inheritable form of mental retardation is Fragile X. Children with the disorder can be diagnosed as early as 2-years-old, with IQs about 35 to 65 points below normal.
But a study suggests the disease is much simpler than previously thought, and existing medication?derived from plant extracts?may be able to treat it.
According to the study, published in the Nov. 30 issue of the journal Cell, a defective Fragile X gene causes excessive production of a protein that controls the stability of a nerve cell’s skeleton. This causes extreme nerve cell growth, which interferes with the flow of information within the brain.
There are drugs already on the market that could counteract the abnormal growth. Some come from plant extracts and are used to treat cancer, according to Kendal Broadie, a U biology professor and one of the lead authors.
The Fragile X gene is involved in protein regulation. Prior to the study, it appeared that hundreds of proteins were being synthesized incorrectly to cause the disease.
But according to the study’s results, only one matters, he said. This greatly simplifies the process of devising a treatment.
Tubulin, the structural protein affected by Fragile X syndrome, is dynamic?constantly growing and shrinking.
A defective Fragile X gene no longer produces its protein. As a result, the cell produces too much of a separate protein. The second protein not only keeps tubulin from degrading but causes it to grow excessively.
“Imagine your skeleton becoming fused at the joints so you could barely move,” Broadie said.
Something similar happens within the nerve cells, except they also have trouble moving food and other things internally.
In someone with Fragile X, the nerve cells of the brain form too many synapses that often appear immature?disrupting the circuits necessary for learning, memory and thinking.
“Information flows in the wrong direction, or it may not be flowing at all,” Broadie said.
For the study, researchers identified the Fragile X gene in fruit flies. When the gene is defective, the flies displayed symptoms resembling human ones. The flies looked normal, could move but could not perform complex tasks like flying.
If a fly with a Fragile X-like condition lost its ability to produce the protein responsible for excessive tubulin growth, the fly functioned normally.
In human beings, neural development occurs most rapidly in the first five or six years of life, Broadie said. It’s possible that early diagnosis and treatment could reduce, or even prevent, the defects among young children afflicted with the disease.