A great deal is known about how model organisms such as fruit flies, nematodes and mice develop. But what about beetles, frogs, and birds? Scientists who study gene function in non-model organisms may get a boost from a new technique developed by Nipam Patel, Ph.D., assistant professor of organismal biology & anatomy and Howard Hughes Investigator at the University of Chicago.
Patel's technique allows scientists to introduce desired genes directly into embryonic cells using the baculovirus, which normally infects and reproduces in only a few species of moths. He has used the virus to carry foreign genes into frog and beetle, as well as fruit fly embryonic cells and believes the virus will prove effective in a wide range of other species.
The results of his findings are published in the November 18 issue of Current Biology.
"The baculovirus vector can easily infect a wide range of species," says Patel. "But outside of its normal moth h ost, the virus is unable to replicate, so there are minimal side effects."
Previously, the opportunity to study gene expression in non-model organisms was very limited. Techniques to create animals in which new genes are permanently inserted into their genomes have only been established for a few animals. Even then, the usefulness of these transgenic organisms is only realized after several generations. This pre sents a problem when studying animals with generation times measured in months or years.
Since the baculovirus can't reproduce outside of its normal moth host, infection is limited to cells near the injection site. This allows researchers to target experimental genes to specific areas.
As infected cells divide, the introduced genes eventually become diluted. But researchers who study developmental processes that occur early in embryogenesis need the genes to work for only a short time in order to test their theories.
Patel has already used this technique to study the gene 'wingless' (wg) in Tribolium, or the red flour beetle. In Drosophila, the role of wg in segmentation has been well documented. Wg codes for a signal molecule which is required for the maintenance of expression of another protein, called 'engrailed' (en ). Together, wingless and engrailed direct segment polarity--which determines the pattern in both the skin and nervous system of each segment. Patel wanted to test whether the function of wingless was conserved in the flour beetle.
Using the baculovirus system, Patel and colleagues first showed that this system faithfully replicated the genetic data from Drosophila. Then using the virus to express wingless in Tribolium, they showed that in the flour beetle, wingless also regulates the expression of engrailed, as in Drosophila.
Future experiments are planned to compare and contrast limb development in beetles, fruit flies and other animals.
Already clinicians are interested in using the new technique to learn more about human gene function. Patel is currently collaborating with Louis Philipson, M.D., Ph.D., associate professor and acting chief of endocrinology at the University of Chicago Hospitals, who studies the effects of genes that regulate insulin secretion.
"Pancreatic islet cells are a lot like brain cells in that they have interesting electrical properties that are crucial to their proper functioning," says Philipson. "We want to study how certain genes modify insulin secretion. Until now, the methods to do this have been very harsh on the cell membrane, and disrupt electrical impulses. The baculovirus turns out to be the most gentle way to get genetic material into these cells and there is no worry about other effects of the virus on the cells," says Philipson.
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