The research of Dr. Paul Mozdziak, assistant professor of poultry science, and Dr. James Petitte, professor of poultry science, resulted in successfully transferring a gene into a chicken and establishing a line of chickens carrying that specific marker gene.
Currently, the chick embryo is often used as a model to understand normal and abnormal embryo development. The new lines of transgenic chicken provide a new tool that can be employed in studies aimed at understanding birth defects such as limb deformities and spina bifida. The researchers say learning the mechanisms behind how cells behave during embryo development could eventually provide clues to halting developmental disabilities and may lead to other uses not yet imagined, including improvements in human and animal health.
The research appears in the March edition of Developmental Dynamics.
"Although there are people who have made transgenic chickens before, no one has produced a transgenic chicken expressing a reporter gene that can be easily tracked," Mozdziak says. "We can now take cells from our transgenic chicken and put those cells into a chick embryo or another transgenic chicken and see how the cells behave and interact with each other."
"This tool provides the impetus to go to the next level of looking at avian stem cells in embryos, putting these stem cells in different places and seeing where they end up," Petitte says.
The researchers say gene transfer is much more complicated in chickens than in, say, mice. Chicken embryos contain about 50,000 cells before the egg is laid; gene transfer in other mammals involves inserting DNA into just one cell.
Mozdziak and Petitte developed the transgenic chicken by taking a RNA virus, or retrovirus, carrying a reporter gene – the lacZ gene, which is easy to detect and which expresses a protein, beta-galactosidase – and injecting it into the blastoderm, or layer of cells on the surface of the yolk, of freshly laid chicken eggs. The eggs were allowed to hatch, and chickens were screened for the presence of the lacZ gene. Eight of 15 male chickens that lived to sexual maturity carried the lacZ gene in their semen, the researchers say.
These eight chickens were then mated with female non-transgenic chickens. Of the chicks produced, two males tested positive for the lacZ gene. These two males were mated with normal females and 50 percent of their offspring contained the lacZ gene as expected.
Further, the second-generation chickens expressed beta-galactosidase, and the lacZ gene is apparently stable from generation to generation.
Petitte says that other transgenic chickens have carried the lacZ gene, but that this is the first time that a transgenic chicken line that expresses beta-galactosidase has been developed.
"This is a really powerful research tool, and it's the first time anyone has had this tool in avian biology," he said.
Note to editors: An abstract of the Developmental Dynamics paper follows.
"Development of transgenic chickens expressing bacterial beta-galactosidase"
Authors: P.E. Mozdziak , S. Borwornpinyo, D.W. McCoy, J.N. Petitte, Department of Poultry Science, North Carolina State University
Published: March 2003 edition of Developmental Dynamics
Abstract: Replication-defective retroviral vectors are efficient vehicles for the delivery of exogenous genes, and they may be used in the generation of transgenic animals. The replication-defective retroviral SNTZ vector carrying the lacZ gene with a nuclear localized signal was injected into the subgerminal cavity of freshly laid eggs. Subsequently, the eggs were allowed to hatch, and the chickens were screened for the lacZ gene by using the polymerase chain reaction. Eight of 15 male chickens that survived to sexual maturity contained the lacZ gene in their semen. Subsequently, these males were mated with wild-type female chickens. From one of the eight lacZ-positive G0 males, two lacZ-positive male chickens were produced from a total of 224 G1 progeny for a germline transmission rate of 0.89%. Both G1 male chickens carrying the lacZ gene were mated with wild-type female chickens and 46.5% of the G2 progeny contained the lacZ gene, which is consistent with the expected Mendelian 50% ratio for a heterozygous dominant allele. The product of the lacZ gene, nuclear localized beta-galactosidase, was expressed in primary myoblast cultures derived from G2 chickens, and it was also expressed in whole G2 chicken embryos.
Media Contacts:
Dr. James Petitte, 919-515-5389
Dr. Paul Mozdziak, 919-515-5544
Mick Kulikowski, News Services, 919-515-3470
Journal
Developmental Dynamics