On the powerful microscope’s television monitor, a single-celled mouse embryo resembles the bumpy surface of an orange peel. A pipet slimmer than a pin–which looks more like a sword after being magnified 400 times–pierces the outer membrane of the embryo and fumbles toward the nucleus. The end of the pipet slides into the center of the nucleus, where research technologist Tom Salada injects foreign DNA. The procedure is another small success story for science, and all in a day’s work for the Penn State Transgenic Mouse Facility (TMF).

Research technologist Tom Salada injects a DNA construct into a mouse embryo at the University's new Transgenic Mouse Facility, which helps reserachers test the effects of gene sequences.

This University Park campus facility, housed in the Department of Dairy and Animal Science, provides services for Penn State researchers who want to test the physical effects of a certain gene or gene sequence. Researchers decide which piece of DNA they want expressed in the mouse, then “cut and paste” to create the desired genome segment. The segment, called a DNA construct, is then replicated in bacteria, isolated from the other parts of the DNA, and sent to the TMF in a vial for integration into the mouse embryo.

More than 150 embryos a day are injected with DNA constructs, and from these, about 50 mouse pups are created. A couple of pups from the batch will successfully integrate the DNA, and only two or three are needed for researchers to test their DNA sequence.

The quality and size of the DNA construct determine its success rate for integration, says Cindy McKinney, the facility’s director. “If a construct is too large or was damaged during the cut-and-paste process, it will not function correctly in the mouse’s genome.” Since opening in October 1999, the TMF team has completed several rounds of successful integrations.

The transgenic mice are raised in the back of the limited access lab, currently located in Central Biological Laboratories on Hastings Road. “The mice pups must be weaned from their mother, so they cannot be separated when they are young,” McKinney says. “Once the pups are old enough, they are sent back to the researcher who prepared the construct.”

The specialized machines on the lab tables are a reminder of how detailed genetic work can be. “Semi-automated machinery is essential,” McKinney says. “If we were working with frog eggs, we could puncture the cell membrane with a needle. But we need state-of-the-art equipment to work with the small mouse eggs and DNA.”

The start-up costs for the facility were provided by the college with additional funding from the Life Sciences Consortium and the Eberly College of Science, says McKinney, who previously worked at the University of Virginia’s transgenic facility.

“This technology is a stepping stone to cloning,” McKinney says. “It also bridges the gap between genomic sequencing and gene function. There are many genes without a known function. I can envision making a transgenic mouse with an overexpressed gene, which will enhance a specific genetic trait of an organism by producing extra copies of the gene’s DNA code. If the extra copy is integrated into the mouse’s DNA, the researcher may obtain clues about the gene’s function.

“Mice are ideal for genetic research because their size makes these complicated, complex studies cost-effective,” McKinney says. “Once we develop the transgenic expertise in smaller animals, we can apply the techniques to larger animals.”

The benefits for such research extend far beyond mice in a lab. “The immune systems in humans and animals are similar,” says Channa Reddy, head of veterinary science. “Transgenic technology will help scientists learn about disease processes in both animals and humans, and could lead to cures for genetic disorders. We can use these mouse models to study cancer, bacterial infections, disease resistance, and livestock improvements. For instance, one could alter the genes of a cow to increase milk quality and quantity.”

Before the TMF opened, most Penn State researchers used commercial transgenic services. “The commercial services were extremely costly,” says veterinary scientist Don Wojchowski. “We have experienced other problems with these companies, such as lack of timeliness and the presence of pathogens in the mice upon arrival. The TMF and McKinney’s expertise have allowed us to prepare mice successfully at a much more rapid rate.”

Terry Etherton, head of dairy and animal science, says he is working with Reddy to obtain funding to bring the TMF closer to researchers on campus and allow for more growth as its services increase. “The new location will provide a barrier laboratory, which means it will be pathogen-free” Etherton says. “The animal cages will be ventilated individually to prevent odor, and the air that enters the facility will be filtered. The air pressure will be higher inside the facility, so when a technician opens the door, the air will rush out to prevent internal contamination. This facility will essentially be the same as an operating room in terms
of cleanliness.”

Reddy believes that the demand for transgenic technologies at the University will continue to increase as genetics research becomes integrated into many colleges’ studies. “In order to compete with other universities and the scientific community around the country, we must have cutting-edge technology available right on campus,” Reddy says. “The TMF at Penn State allows us to perform research at a state-of-the-art level.”

—Rebecca Zeiber