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Hemophilia Summary Essay


-Hemophilia A is an inherited disorder in which one of the proteins needed to form blood clots is missing or reduced. This lacking protein is known as blood clotting factor 8. Without F8, the blood cannot clot properly to stop bleeding and can result in excessive bleeding or disabilities.

Hemophilia A
-When blood is not able to clot and allow wounds to heal, this is a result of Hemophilia A
Symptoms Include:
-Prolonged bleeding from cuts
-Excessive nose bleeds
-Many large bruisings
-1 in 5,000 males are affected

Blood Coagulation

-Blood coagulation is the defensive process that causes blood to clot and helps prevent excessive blood loss when blood vessels are injured. -Coagulation is a complex process that involves 20 to 30 components, called blood coagulation factors, and a series of complex chemical reactions. -When a blood vessel is injured, platelets in the area of the damage clump together and stick to the edges of the cut to begin the coagulation process. -Platelets are fragments of cells containing clotting factors and play a major role in blood clotting. -These clotting factors help platelets stick together and activate fibrin.

(These clotting factors combine with a protein called prothrombin in a reaction that converts prothrombin to thrombin. Thrombin then converts fibrinogen (a protein present in plasma) into long, sticky threads of another protein called fibrin) -The fibrin forms a mesh-like net over the opening and traps red blood cells as they try to leak out of the cut. -As the clot hardens, it forms a protective seal over the cut so that the injury can heal and the vessel wall can be restored.

Factor 8

-One specific intrinsic clotting cofactor that stabilizes the fibrin clot is Factor 8. -F8 is activated by thrombin in the presence and is a cofactor in the activation of factor X (WHAT DOES X DO??) -Ultimately Factor F8 cross-links fibrin polymers solidifying the clot. -Without this coagulation factor, vessels are not able to heal and therefore result in excessive bleeding (also known as Hemophilia A)

Causes of F8 deficiency

-Numerous mutations in the gene structure have been discovered. -Genetic abnormalities include genetic deletions of variable size, abnormalities with stop codons, and frame-shift defects. -Data suggest that 45% of severe hemophilia A cases result from an inversion mutation.

F8 Gene

-the F8 gene is located in the proximal part of chromosome X and is expressed in human liver, spleen, lymph nodes, and a variety of other tissues, -It’s one of the largest genes; it is 186 kilobases (kb) long and has a 9-kb coding region that contains 26 exons and 25 introns. -The shaded green region to a full blue and incomplete red displays that the gene gets transcribed into mRNA but not translated into proteins. Shaded green is the 5′ and 3′ untranslated regions that are able to bind to something else.

-variant (1) consists of 26 exons and encodes the full-length isoform (a)
-variant (2) contains an unique 5′ exon located within intron 22 of transcript variant 1

Crystal Structure

Is composed of a Ca Ion, Cu Ion, Alpha-D-Mannose & N-Acetyl-D-Glucoamine. (Find out the importance/functions of these..?) Arrows = beta sheets
Coils = alpha helix
-how the F8 factor is incorporated / works in the overall protein.

-responsible for generating the larger amounts of Xa and thrombin required for clot formation.

-Covalent cross-linking of fibrin polymers by activated factor XIII (XIIIa) is required for adequate clot strength and normal wound healing.

-How it works: catalyzes a transglutamination reaction that initially cross-links the C-terminal ends of the g chains on adjacent fibrin monomers.

Intrinsic / Extrinsic

It turns out that you actually need both the intrinsic and extrinsic pathways in your body. In a test tube, you can form fibrin along either pathway. But in the body, the pathways are intertwined in such a way that if you’re missing something on either the extrinsic or intrinsic side, you won’t be able to clot properly.

In our bodies, the thing that kicks off the clotting cascade is tissue factor “exposure.” Tissue factor is not floating around in the blood normally – or at least, it isn’t normally “visible” to the blood (it might be in little membrane fragments, but it’s not active until it’s needed). When you need to form a clot, tissue factor appears, and together with factor VIIa (which happens to be just floating around in the blood) it converts factor X to Xa (which then converts prothrombin to thrombin, which converts fibrinogen to fibrin). So: clotting initially begins along the extrinsic pathway.

The weird thing, though, is that as soon as we make a little Xa, that Xa (along with the aptly-named tissue factor pathway inhibitor) turns off the extrinsic pathway! A little thrombin is formed, though, before the pathway gets turned off – and that thrombin kicks off the intrinsic pathway (the other side of the cascade, with factors VIII and IX). Fibrin formation then proceeds along this pathway until it’s no longer needed.

The bottom line is: you need both the intrinsic and extrinsic pathways to form fibrin in vivo. If you don’t have factors VIII or IX, you can’t utilize the intrinsic pathway – and you’ll have a very hard time forming fibrin!

Intrinsic / Extrinsic

Include the two different pathways that lead to the formation of a fibrin clot: the intrinsic and extrinsic pathway. Although they are initiated by distinct mechanisms, the two converge on a common pathway that leads to clot formation. Both pathways are complex and involve numerous different proteins termed clotting factors.

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