Swine breeders and medical researchers have some new tools for genetic research, thanks to a team of scientists led by an Iowa State University professor.
The group created a library of 21,499 pig gene sequences and mapped the locations of 727 of those genes on pig chromosomes. Researchers can access the sequences--chunks of DNA, the chemical that carries the genetic code of living things--to further identify and map pig genes.
"This is a tool for the scientific community," said Iowa State animal science professor Christopher Tuggle, leader of the multi-state project. "People will now be able to do their research better, faster and more accurately. We demonstrated that by mapping 727 genes."
The sequences are useful for "mapping" a gene's location on the chromosomes present in every cell. The 727 genes represent about a third of the 2,000 pig genes that have been mapped worldwide.
The project focused largely on genes expressed in tissues associated with female pig reproduction and growth: the pituitary gland, placenta, uterus, embryo, hypothalamus and ovary.
The group obtained expressed sequence tags, or ESTs, for 21,499 genes. ESTs are chunks of 300 to 700 base pairs -- the chemical code carried by DNA. An EST isn't a gene's entire code, but enough unique combinations of bases to identify the gene.
They're called "expressed" tags because they identify only genes that are actually governing the cell's function. By focusing just on expressed genes, "The biology is telling us what's important" to study, Tuggle said.
The research group has posted the ESTs on the Internet and developed software tools that compare them with databases of human and pig gene sequences -- a process that can help map the genes and determine their functions.
The three-year project, financed with $700,000 from the U.S. Department of Agriculture included researchers from the universities of Iowa, Missouri and Nebraska, and the National Center for Genomic Resources,
The project also produced probes to detect the expression of specific genes in pigs. Swine breeders can use the probes to see if a gene is expressed, or active, in a pig and breed animals with desirable gene expression, Tuggle said.
Scientists also could use the sequence information to manipulate pig genetics. Randy Prather of the University of Missouri is developing small pigs whose organs may be transplanted into humans. "He can modify and make a specific change (to the pig genome) and to do that he can use the information the project has provided," Tuggle said. Prather is a collaborator in the project.
Biomedical researchers are interested because they see pigs as a model for human disease, Tuggle said. University of Iowa researchers are interested in studying gene expression in placental tissues for clues to how placental cancers develop in humans.
The Pig Expressed Sequence Tag database is on the Web at http://pigest.genome.iastate.edu/summary.html.
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