Coagulation factor IX deficiency causes hemophilia B in humans. We have used gene targeting to develop a coagulation factor IX-deficient (factor IX-knockout) mouse strain. Mouse embryonic stem (ES) cells were targeted by a socket-containing vector that replaces the promoter through exon 3 of the factor IX gene by neoDeltaHPRT, which is a functional neo gene plus a partially deleted hypoxanthine...

Hemophilia B Leyden is characterized by low levels of factor IX antigen and activity before the age of 15, whereas after puberty factor IX levels rise at a rate of about 5% per year. A single base substitution (-A----T) at position -20 was identified in the putative promoter of the gene cloned from a patient with hemophilia B Leyden. This nucleotide change was confirmed in a second patient from...

Hemophilia B, also known as Christmas disease, arises from mutations in the factor IX (F9) gene. Its treatment in humans, by recombinant protein substitution, is expensive, thus limiting its application to intermittent treatment in bleeding episodes and prophylaxis during surgery; development of inhibitory antibodies is an associated hazard. This study demonstrates permanent therapeutic correct...

Factor IX is synthesized in a precursor form with a propeptide that contains the gamma-carboxylation recognition site, an element which directs the post-translational gamma-carboxylation of adjacent glutamic acid residues. After protein synthesis, the propeptide is cleaved to yield the mature Factor IX. To study propeptide processing, anti-proFactor IX antibodies were prepared using a synthetic...

We demonstrate the controlled rotation and torque generated by uniaxial magnetic microactuators formed by two bound superparamagnetic particles in a fluid. The torque and rotation are precisely controlled by rotating magnetic fields, generated by an external electromagnet or by on-chip current wires. We present the magnetic energy equations and the equations of motion for two-particle microactu...

We have recently discovered unusual sugar chains (xylose (Xyl)-glucose (Glc) and (Xyl)2-Glc) linked to a serine residue in the epidermal growth factor (EGF)-like domains of human and bovine clotting factors VII (Ser-52), IX (Ser-53), and protein Z (Ser-53), in addition to bovine platelet glycoprotein thrombospondin. We now have evidence of another modification in the first EGF-like domain of hu...

The role of the factor IXa heparin-binding exosite in coagulation was assessed with mutations that enhance (R170A) or reduce (R233A) stability of the protease-factor VIIIa A2 domain interaction. After tissue factor (TF) addition to reconstituted factor IX-deficient plasma, factor IX R170A supported a 2-fold increase in velocity index (slope) and peak thrombin concentration, whereas factor IX R2...

The role of the factor IXa heparin-binding exosite in coagulation was assessed with mutations that enhance (R170A) or reduce (R233A) stability of the proteasefactor VIIIa A2 domain interaction. After tissue factor (TF) addition to reconstituted factor IX-deficient plasma, factor IX R170A supported a 2-fold increase in velocity index (slope) and peak thrombin concentration, whereas factor IX R23...

Hemophilia B Leyden is characterized by unusual developmental regulation of factor IX synthesis in affected individuals. One family affected with the hemophilia B Leyden phenotype was found to have a specific single-base mutation (G----A) at nucleotide -6 of the factor IX gene. The mutation site was found in a small region of the 5'-untranslated sequence designated the Leyden-specific region (L...

Previous studies have shown that thrombin generation in vivo caused a 92% decrease in factor IX (F.IX) activity and the appearance of a cleavage product after immunoblotting that comigrated with activated F.IX (F.IXa). Under these conditions, the fibrinolytic system was clearly activated, suggesting plasmin may have altered F.IX. Thus, the effect(s) of plasmin on human F.IX was determined in vi...