Untangling the myosin mystery

Posted 12/20/02 • James Donnelly and Michelle Chin '03

Thanks to the work of Dartmouth undergraduate Reid Thompson '03, a senior from Livingston, N.J., scientists are learning more about the evolution of myosins, the motors of the cellular world. Myosins are cell proteins integral in everything from muscle contraction to cell division. There are at least 18 separate classes of myosin, but not all of them are found in every organism. For example, humans utilize 12 myosins while mollusks get by with just a few.

Thompson was able to seize on this difference to help answer an important question: where did all these myosin classes come from and how did they develop?

As the principal investigator for an article published recently in The Anatomical Record's special astrobiology issue, Thompson studied 65 different organisms' myosins. Based on the similarities and differences, he constructed an evolutionary tree that spanned everything from protozoa to people. The result is a more complete evolutionary history of the protein.

"Since we know humans and mice evolved from a common ancestor and we know that humans have a certain kind of myosin, we can predict that the same myosin should be present in the mouse, even if we haven't found it yet," he says.

Thompson's results have important implications for the study of myosins. He shows that early evolved myosins developed as generalists, performing a variety of cell functions. More recently evolved myosins, such as some of those found in humans, have specialized functions and may exist in only a few organisms or a few cell types within those organisms.

"This study represents a major contribution to the field and a new direction for my laboratory," says George Langford, the E. E. Just Professor of Natural Sciences and a professor of biological sciences at Dartmouth, who co-authored the study. "This work was an extraordinary accomplishment for an undergraduate."

Langford runs the George Langford Lab at Dartmouth College and is a researcher at the Marine Biological Laboratory in Woods Hole, Mass.

"I encouraged Reid to write the paper on the evolutionary history of the myosin superfamily because when I first introduced the idea to him, he reacted very positively," says Langford. "He came back to me after thinking about the project for a couple of days with a plan for the paper that was far more comprehensive than my original idea. I was simply amazed at his level of sophistication."

Thompson's research was funded in part through a Dartmouth Presidential Scholar Program, which provides opportunities for students to work with faculty as research collaborators during their junior and senior years.

Thompson feels the opportunity to publish as an undergraduate has encouraged him in his steps toward becoming a scientist. In addition to the current paper, Thompson contributed to two projects in Langford's lab this summer, the results of which were published in the October 2002 issue of Biological Bulletin.

-James Donnelly and Michelle Chin '03