The Regulation of Blood Coagulation 
J. Evan Sadler, M.D., Ph.D. — Associate Investigator 
Dr. Sadler is also Associate Professor of Medicine and of Biochemistry and Molecular Biophysics at Wash- 
ington University School of Medicine. 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. 
Abnormal thrombosis also complicates many 
common 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. 
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 patients treat transfused vWF as a 
foreign protein and make inhibitory antibodies to 
it. Deletions in the vWF gene appear to 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. Severe 
bleeding in certain variants can be associated ei- 
ther with increased or decreased binding of vWF 
to a specific receptor protein on platelets. Among 
nine such unrelated patients, five different muta- 
tions were characterized in a small vWF domain 
that appears to modulate the affinity of vWF for 
this platelet receptor. This illustrates the impor- 
tance of proper balance between increased and 
decreased vWF function for normal hemostasis. 
A newly described variant of von Willebrand 
disease, first recognized in Normandy, France, is 
characterized by defective binding of vWF to 
blood coagulation factor VIII. In such patients 
factor VIII is unstable, and this results in a second- 
ary factor VIII deficiency that mimics classical 
hemophilia. A missense mutation was identified 
in the factor VIII binding site of vWF. The corre- 
sponding recombinant vWF exhibited the same 
defect in factor VIII binding as natural vWF Nor- 
mandy, confirming that this mutation causes the 
disease. The genetic defects of these and other 
such patients provide insights into structure- 
function relationships of vWF and may suggest 
new therapeutic strategies to inhibit or augment 
vWF function. 
Thrombomodulin and Thrombin 
Thrombomodulin is a protein of the endothe- 
lial cell surface that binds thrombin, a blood clot- 
ting enzyme. Because of its effects on thrombin 
activity, thrombomodulin is an essential natural 
anticoagulant. Several inflammatory mediators 
decrease the expression of thrombomodulin by 
endothelial cells. Understanding this process 
may help us to understand the abnormal blood 
coagulation that accompanies much human dis- 
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