Molecular Genetics of Blood Coagulation 
increased blood clot formation. Thus an under- 
standing of the structure and function of plasmin- 
ogen activator inhibitor- 1 and of its interaction 
with plasminogen activators is of great signifi- 
cance in the study of the fibrinolytic system and 
its role in many important human diseases. 
For these reasons we have cloned the gene for 
human plasminogen activator inhibitor- 1 and 
have characterized its structure. We have suc- 
cessfully produced recombinant human plasmin- 
ogen activator inhibitor- 1 in bacterial cells and 
are using this system to explore its interactions 
with other components of the clotting system and 
to determine which portions are most important 
for its functions. This work should lead to an im- 
proved understanding of the role of the fibrino- 
lytic system in human diseases and to the develop- 
ment of new treatment approaches for these 
important disorders. 
Bone Marrow Transplantation 
Bone marrow transplantation is being used 
with increasing frequency to treat a variety of dis- 
eases, including several types of leukemia and a 
number of other cancers. In this procedure, doses 
of radiation and chemotherapy are given that are 
designed to destroy the patient's bone marrow 
and would ordinarily be fatal. The patient is then 
"rescued" by the transplantation of normal bone 
marrow from a healthy donor. 
We have used DNA probes to study the patient's 
blood cells after the transplant, to determine 
which cells have come from the donor bone 
marrow and which have come from any remain- 
ing patient bone marrow that survived the proce- 
dure. With recent advances we have been able to 
extend this approach to study the origin of even a 
single blood cell. In addition to increasing our 
understanding of the biology of bone marrow 
transplantation, this information may prove use- 
ful in directing treatment after the transplant and 
may help predict which patients are at risk for 
specific complications. 
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