The findings are published in the Nov. 26 issue of the journal Nature.
The Notre Dame researchers and scientists at Flemish Interuniversity Institute for Biotechnology at the University of Leuven in Belgium developed a strain of mice missing the gene to produce Factor VII, a protein critical to initiating blood coagulation.
In an earlier study, mice embryos deficient in a related coagulation protein known as Tissue Factor failed to develop normally, with most embryos dying midway through gestation. Since Factor VII and Tissue Factor are known to bind together to form a complex to initiate coagulation, the investigators expected the Factor VII experiment to produce results similar to the Tissue Factor study.
But contrary to the scientists' expectations, Factor VII deficient mice embryos developed normally throughout gestation although, once born, the mice suffered fatal perinatal bleeding.
"We knew that these proteins were related in blood coagulation, but this study shows that Tissue Factor must play a role in embryonic development that doesn't involve Factor VII," says Francis J. Castellino, dean of Notre Dame's College of Science, Kleiderer-Pezold professor of biochemistry and director of the Transgene Center. "This unexpected conclusion of our study opens up a new avenue of exploration of the unsuspected role of coagulation proteins in prenatal development."
According to Castellino, mice are good animals in which to study human blood diseases and at the present time are the only animals in which targeted gene manipulation of the kind used in these studies is advanced enough for this level of investigation.
While the field of targeted gene manipulations is in its infancy, according to Castellino, it gives scientists a clearer view of the complex interplay of all genes involved in particular blood diseases, such as heart disease and hemophilia. Learning how coagulation proteins function in a living organism also shows whether cells have some backup mechanisms for clotting and clot dissolving.
Additionally, such studies eventually may provide clues to whether other body processes -- such as the production and spread of tumors -- are effected as well.
Elliot Rosen, associate director of Notre Dame's Trangene Center, and three Notre Dame graduate students worked with Peter Carmeliet and associates in the laboratory of Désiré Collin at the Belgian university, which is at the forefront in targeted transgenic manipulations.
Future studies will have to address whether the Factor VII protein was transferred from mother to embryo in utero, says Rosen. "Very sophisticated experiments will help us determine that. At this time, through initial investigation, we believe it's highly unlikely that significant mother to embryo transfer occurred. We also think it's unlikely that blood coagulation is not necessary for embryonic development, particularly since other blood coagulation proteins are required. These results suggest that other blood coagulation-related proteins may have additional functions during embryonic development."
In related research, the Notre Dame and Leuven groups collaborated with scientists at Washington University in St. Louis to cross-breed Factor VII-deficient heterozygotes with mice deficient in Tissue Factor Pathway Inhibitor, another coagulation regulator. Again surprisingly, the scientists found that the Factor VII deficiency counteracted the lethal consequence associated with the Tissue Factor Pathway Inhibitor deficiency in embryos.
This study is being presented at the American Society of Hematology meeting Dec. 5-9 in San Diego by two Notre Dame graduate students, Louise Jalbert and Joyce Chan. One of these papers has received the annual reward of the American Society of Hematology for the most outstanding work by a graduate student.
For more information, contact Castellino in his office at (219) 631-6456 or Rosen in his office at 631-9365.
Journal
Nature