Mutant genes may have affected Lincoln

By By Paige Fieldsted

By Paige Fieldsted

Abraham Lincoln was famous for the Gettysburg address, freeing the slaves and his awkward gait he walked.

And new research suggests that Lincoln had spinocerebellar ataxia type 5 (SCA5), a disease that attacks and degenerates the nervous system.

A study done by the U’s brain institute may have found an explanation for SCA5. When a normal person bends a knee or elbow, his or her tiny nerves bend and stretch but do not break.

“We found that a protein called beta-spectrin is what keeps neurons from breaking. Every time you move, you stretch your nerves, and beta-spectrin is what enables them to stretch without breaking,” said Marc Hammarlund, postdoctoral researcher in biology.

SCA5 is a neurodegenerative disease that is caused by a mutation in the beta-spectrin gene.

Research on the beta-spectrin gene is done on nematodes, commonly known as worms.

“At the molecular level, the nerve cell of a nematode is the same as a nerve cell of the human brain, because evolution designed the nervous system once and has used it for all higher organisms,” said Erik Jorgensen, biology professor.

The worms were covered with a chemical that would seep through their porous bodies and destroy the beta-spectrin gene.

“When we got rid of the beta-spectrin gene, their nerves snapped when they bent or stretched,” Hammarlund said.

Michael Bastiani, professor of biology, said, “The worm’s neurons progressively degenerate in a way that is very similar to what is seen in human neurodegenerative diseases.”

“Human mutations that cause SCA5 are in beta-spectrin, but humans have four genes that create beta-spectrin; worms only have one. The mutation in humans may or may not result in the same weak nerve effect,” Hammarlund said.

Jorgensen said, “In the worm, we completely eliminated the beta-spectrin protein. In humans, only a segment of it has been removed. There is still some beta-spectrin being made.”

In order for researchers to find out whether beta-spectrin mutations weaken or break nerves in humans, studies need to be done in animals with similar genes.

Mice are the animal of choice, because humans are identical to mice except for 200 out of 25,000 genes.

“What needs to happen is that the mutations that eliminate the beta-spectrin gene need to be studied in mice,” said Jorgensen.

Bastiani said, “Eliminating the protein in mice would also be great as a disease model to study treatments that might cure or delay the onset of the human disease SCA5.”