A researcher studying the last common link between invertebrate and vertebrate animals has found a key genetic change that separates the spineless from the backboned.

Jeremy Gibson-Brown, Ph.D., assistant professor of biology at Washington University in St. Louis, studies amphioxus, a small marine worm, a primitive invertebrate species that is the closest living invertebrate related to vertebrates like ourselves. Gibson-Brown has found that a gene involved in the development of a body layer in invertebrates duplicated within the vertebrate lineage after the development of amphioxus.

However, in vertebrates, this gene, AmphiEomes/Tbr1, gave rise to two genes, Eomesodermin and T-brain-1, involved in brain development. While the vertebrate Eomesodermin gene has retained its original function in forming the mesoderm, or "middle skin" layer,in all vertebrate studies from fish, to amphibians to humans, the duplicate copy has lost that function and instead has evolved a role in forebrain development.

"This shows us how old genes can give birth to new ones, and how the origins of novel developmental functions can be traced," said Gibson-Brown, who will have his results published in a forthcoming issue of the Journal of Experimental Zoology. His next step will be to look for these genes in lampreys, primitive jawless fish similar to the ancestors of later vertebrates.

"I want to see whether this gene duplication predated the separation of jawless fish and vertebrates and whether the role in forebrain development had yet been acquired."

Fruit flies, mice, worms and apes share an amazing amount of genetic information with us humans and with each other. For instance, there is only one-tenth of one percent genetic variation between a human and a chimpanzee.

A field of research has arisen to address what kinds of genetic change over time have occurred in different species to account for so many physical differences despite such gene
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Contact: Tony Fitzpatrick
tony_fitzpatrick@aismail.wustl.edu
314-935-5272
Washington University in St. Louis
16-Apr-2002