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Researcher traces gene development in 'last common link'

Media assistance: Tony Fitzpatrick - (314) 935-5272
Source: Jeremy J. Gibson-Brown's Web page - (314) 935-4467

By Ellen Thompson

[St. Louis, Mo., April 2002] - 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.

Meet our shared ancestor.

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 genetic similarity. It is called evolutionary development. "Evo-devo," as Gibson-Brown affectionately refers to this budding discipline, combines the principles of traditional evolutionary and developmental biology in examining the change in gene sequence and regulation that over time lead to the development of new species and eventually new body plans.

Amphioxus and humans go 'way back'.

"We seek to unravel the history of the evolution of developmental programs in animals," Gibson-Brown explained.

Gibson-Brown is studying the evolution of T-box genes, a group of genes that encode transcription factors regulating gene expression in embryogenesis, or the development of embryos. Simply put, T-box genes control when and where a particular gene is turned on (expressed) or turned off during the course of an animal's development. The vast diversity of body plans seen in animals alive today - and those who have lived in the past - are due in part to different expression patterns of these genes. T-box genes are present both in vertebrates and invertebrates, and so offer valuable insight into the emergence of new developmental programs, and hence new body plans, during the course of evolution.

Amphioxus is a small marine worm, a primitive invertebrate species whose last common ancestor with humans lived 600 million years ago. Amphioxus is the closest living invertebrate relative to the vertebrates, making it a very attractive target for Gibson-Brown's research. He is interested in how these T-box genes, present in Amphioxus, humans and everything in between, have adapted their function and expression patterns to yield such a vast array of body plans, from worms to mice to humans.

"What I've been looking at is where and when these T-box genes are expressed in the development of amphioxus in order to understand the function of those genes in the last common ancestor of amphioxus and humans," Gibson-Brown said.

He has just begun work with lampreys, a very primitive vertebrate and one of the last species of jawless fish still alive today. Because lamprey ancestors evolved relatively shortly after the divergence of vertebrates from invertebrates they provide the next stepping stone in the story of T-box gene evolution.

By comparing the expression of T-box genes in Amphioxus, lamprey and mice, Gibson-Brown hopes to better understand the role that changes in gene regulation have played in the evolution of T-box genes.

"I want to understanding the regulatory elements controlling the expression of T-box genes in different species because the evolution of new developmental functions by genes is primarily achieved by the evolution of regulatory elements," he said.