In the much simpler nematode, there are too few cells in early embryos to form actual layers. However, just one cell, which is analogous to the mesoderm layer of vertebrates, produces muscles, a feeding apparatus that resembles a heart and cells that are comparable to blood. As with vertebrates, the endoderm of the nematode also differentiates into a gut organ.
In the C. elegans embryo, when there are only four cells, a single cell is selected to produce mesoderm and endoderm organs. Despite the enormous differences, remarkably, it appears that the same genes operate at that stage to control that selection in both the worm and vertebrate animals, said Rothman.
This implies that the common ancestor from many hundreds of millions of years ago, shared by both humans and worms, used the same early regulatory machinery. The invention of groups or layers of cells that could ultimately produce heart, lungs and other key organs which allow humans to thrive as large animals, evolved from a single event during which this regulatory switch was invented.
Rothman explained that his lab identifies and studies mutant worms that are defective in early development. They then identify the genes causing those birth defects.
"Our goal is to learn about how those genes work and what can go wrong when they are broken. In this way we can hope to learn how to fix them," he said, noting that some of his work is funded by the March of Dimes Birth Defects Foundation.
The information already gathered by scientists includes mapping out the wiring of the worm's entire nervous system, or brain, and the ten thousand interconnections between the nerve cells.
The worm develops quickly, growing from an egg to an adult in three days, as compared to mice, for example, which take several months. In addition to growing quickly, researchers can grow large quantities of the worms for study -- several thousand can
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Contact: Gail Brown
gbrown@instadv.ucsb.edu
805-893-7220
University of California, Santa Barbara - Engineering
29-Mar-2001