The Regulation of Blood Coagulation 
J:) 
J. Evan Sadler, M.D., Ph.D. — Associate Investigator 
Dr. Sadler is also Associate Professor of Medicine and of Biochemistry and Molecular Biophysics at 
Washington University School of Medicine, St. Louis. He obtained his undergraduate degree in chemistry 
from Princeton University. He then attended Duke University, where he received first his Ph.D. degree in 
biochemistry with Robert Hill and then his M.D. degree. Following his internship and residency in 
medicine at Duke University Medical Center, Dr. Sadler was a Hematology Fellow in the laboratory of Earl 
Davie at the University of Washington, Seattle. 
UNDER normal circumstances, blood clots oc- 
cur only at sites of vascular injury, and un- 
necessary clots are dissolved promptly. Inappro- 
priate blood clots can cause devastating illness, 
such as stroke and myocardial infarction. Abnor- 
mal thrombosis also complicates many com- 
mon diseases, including certain cancers and 
infections. 
In the blood, proteins and small cells called 
platelets are required for clot formation. The en- 
dothelial cells that line all blood vessels and cir- 
culating white blood cells are not, however, pas- 
sive bystanders in these reactions, but actively 
promote or inhibit clotting. Compounds that are 
produced during inflammation modulate these 
cellular activities. 
We are investigating the structure, function, 
regulation, and evolution of proteins that control 
blood coagulation. Our goal is to understand how 
these opposing tendencies — to stimulate or to in- 
hibit clotting — are balanced to achieve normal 
hemostasis and prevent dangerous thrombosis. 
These studies will increase our knowledge of the 
interaction between blood coagulation and in- 
flammation and may provide a foundation for the 
design of new therapies for thrombotic disorders. 
Studies of thrombomodulin, thrombin, and tissue 
factor are supported by a grant from the National 
Institutes of Health. 
von Willebrand Factor 
and von Willebrand Disease 
The von Willebrand factor (vWF) is a blood 
protein that is made by endothelial cells and is 
required for normal platelet function. vWF also 
binds to and stabilizes blood coagulation factor 
VIII, the factor that is deficient in classical hemo- 
philia. The structure of vWF was determined indi- 
rectly by cDNA cloning: vWF contains 12 re- 
peated domains that belong to four families of 
ancestral sequences. Hereditary deficiency of 
vWF, or von Willebrand disease, is the most com- 
mon genetic bleeding disorder of humans. Mild 
abnormalities of vWF function can be detected in 
nearly 1 percent of the population. 
We determined the structure of the human vWF 
gene and also of a related pseudogene that has 
diverged recently from the authentic vWF gene. 
This allowed us to investigate von Willebrand 
disease at the level of gene sequence. We charac- 
terized deletions of the vWF gene that cause se- 
vere von Willebrand disease in five unrelated pa- 
tients. These particular patients treat transfused 
vWF as a foreign protein and make inhibitory anti- 
bodies to it. Deletions in the vWF gene predis- 
pose to the formation of such antibodies. 
These studies were extended to include pa- 
tients with variants of von Willebrand disease 
who make a defective vWF molecule. Among 
more than 30 unrelated patients, 1 1 difi'erent 
mutations were characterized within a single 
exon of the vWF gene. Six of these mutations are 
within a small vWF domain that appears to modu- 
late the affinity of vWF for platelets; of these six 
mutations, five cause a paradoxical increase in 
binding and the sixth causes a decrease in bind- 
ing. The remaining five mutations are within an 
adjacent domain of the protein and cause loss of 
function, either by impairing vWF biosynthesis or 
increasing vWF degradation. The association of 
severe bleeding with both increased and de- 
creased function illustrates the importance of bal- 
anced vWF function for normal hemostasis. 
A recently described variant of von Willebrand 
disease, recognized in a patient from Normandy, 
France, is characterized by defective binding of 
vWF to blood coagulation factor VIII. In such pa- 
tients factor VIII is unstable, and this results in a 
secondary factor VIII deficiency that mimics clas- 
sical hemophilia. Among several unrelated af- 
fected families, three diff^erent mutations were 
identified in the factor Vlll-binding site of vWF. 
The corresponding recombinant vWF proteins ex- 
hibited the same defect in factor VIII binding as 
natural vWF Normandy, confirming that these 
mutations cause the disease. The genetic defects 
of these and other such patients provide insight 
into structure-function relationships of vWF and 
may suggest new therapeutic strategies to inhibit 
or augment vWF function. 
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