Monday, May 15, 2006

Horrible Diseases We Love, Chapter Two: Medusa Mutation

Fibrodysplasia ossificans progressiva. About 2500 people in the world have a rather bizarre disease. Their flesh turns to bone, thus making them living statues. The disease converts muscle, tendons and ligaments into bone. Eventually joints are locked into place, making movement impossible.

In childhood, tendons, ligaments, and skeletal muscle begin an inexorable transformation into an armament of bone. Eventually, ribbons, sheets, and plates of bone cross the joints and lock them into place. Surgically removing the extra bone just makes it grow back faster. Slight traumas such as bumps, bruises and injections can stimulate further transformation into bone.

Victims often die, typically in their 40s, from complications related to difficulty breathing as the bone restricts the space available for their lungs to move. There is no effective treatment, other than avoiding much physical activity, but researchers hope the gene’s discovery will change that. From Grumpy Owl


Blogger Mr Lucky Doubles said...

More info: The condition, they said, results from a defect in a natural chain of molecular events called the bone morphogenetic protein signaling pathway, involved in the formation and repair of the skeleton.

The molecule encoded by the newfound gene functions as a sort of “switch,” the scientists explained. The molecule appears in certain stem cells, immature cells that can develop into a variety of different cell types for diverse organs.

The molecule consists of 509 subunits, called amino acids, of which one is defective in the condition, the researchers said: an amino acid known as histidine appears where another one, arginine, should be.

This change somehow affects the activity of the “switch,” they explained, though understanding exactly how requires further study.

“As is the case for most genes, every cell has two copies of the ACVR1 gene,” Shore said. In patients with the disease, one of the two harbors the mutation, which produces a defective version of the molecule.

Whereas the defect in the molecule consists of a substituted amino acid, the defect in the gene itself—which produces that molecule—is a substituted “letter” of genetic code, called a nucleotide.

“The substitution of one genetic letter for another out of six billion genetic letters in the human genome—the smallest and most precise change imaginable—is like a molecular terrorist,” said Kaplan.

3:03 PM  
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