Coagulation Factor VIII

Coagulation Factor VIII

HRF, INC.

 

Coagulation Factor VIII

The demand for Factor VIII has increased drastically over the last few years. This demand has been particularly strong from European countries such as England, France and Spain.  HRF, INC. is one of the only facilities in the US that provides Factor VIII Deficient Plasma, Factor VIII Pooled Plasma and Factor VIII with Inhibitor Plasma.

 

Description

Coagulation Factor VIII is a large glycoprotein plasma that functions in the blood coagulation cascade acting as a cofactor for the factor IXa^[1]. This is dependent on factor X’s activation. Factor 8 is activated proteolytically via various coagulation enzymes including thrombin. In the blood, there is a great association between von Willebrand factor and Factor VIII. Von Willerbrand acts as the protective carrier protein for factor VIII^[2]. The protein is structurally related to ceruloplasmin and factor V while it contains a sequence repeats with an obvious domain structure. In essence therefore, Factor 8 is a serum protein in the coagulation cascade which nucleates the membrane-bound protease complex assembly on an activated platelets’ surface at a vascular injury site^[3].

Expression and Coding

The leading sequence of the pro-protein contains 19 amino-acids that yield a mature protein consisting of 2,332 amino acids^[4]. On the other hand, the deduced precursor protein has a molecular mass of 267 kD and 2,351 amino acids. Factor VIII occurs in 3 copies: A domain consisting of 330 to 380 amino acids; B domain consisting of an estimated 925 amino acids and; 2 C domains of an estimated 160 amino acids^[5]. These domains are arranged; A1-A2-B-A3-C1-C2. The notable repeats in A and C indicate the cysteines conservation whereas the B region sites the N-glycosylation.

The Factor VII is expressed in human lymph nodes, spleen, liver and a variety of other tissues. It is however not expressed in endothelial cells, bone marrow or peripheral blood lymphocytes. Instances such as liver disease do not reduce the factor VIII, on the contrary they elevate it. Elevated levels of factor VII in individuals exposes them to risks of developing pulmonary embolism and deep vein thrombosis^[6]. With understanding that copper is an essential factor cofactor, deficiency in copper is identified as a strategy to decrease factor VIII levels.

Gene Structure

Factor 8 has 186 kb spans and 26 exons^[7]. Under a study^[8], it was that the Xq28 region contains a gene termed as A. The gene hybridized to a region in exon 22 of the factor 8 gene. Now termed as the F8A gene, it is in reverse orientation to the factor VIII (F8) and was contained in intron 22 entirely. The X chromosome contains F8A in three copies. Its adjacent regions are; 1 in intron 22 while 2 upstream and telemetric to the F8 gene transcription start site. On the opposite direction of the F8, gene F8A is transcribed while being completely nested and intron-less with intron 22. There are 2 additional transcribed F8A gene copies on approximately 500 kb of the F8 gene.

Biochemical Features

Factor 8 is an intricate of a large non-covalently bound small fragment and the inert carrier protein that contains the active site^[9]. After a study, leukocytes synthesize some of factor 8 in vitro; however, the liver offers the primary synthesis. Hemophilia A patients normally present the carrier molecule in their plasma. A highly purified human factor 8 consists of a single high molecular weight polypeptide chain with the highest specific activity^[10].

Mapping

Through situ hybridization, it was concluded^[11] that the factor VIII is located in the proximal part of chromosome Xq28 with probes St14 and DX13 located distally. Through a cell line hybrid containing only a terminal Xq28 fragment, the factor 8 probes do not hybridize but the St14 and DX13 hybridize to the cell line’s DNA. Factor VII is oriented on the chromosome with the 5-prime region being close to the telomere^[12].

F8 and Health Conditions: Hemophilia

Mutations in the factor VIII gene results to hemophilia A^[13]. Its treatment requires replacement therapy with purified protein. The structure of a recombinant and fully active form of factor VIII consists of peptides and heterodimer retrospectively containing the A1-A2 and A3-C1-C2 domains. This structure permits unambiguous modelling of the comparative orientations of the 5 domains of factor 8. Comparison and contrast of factor V, ceruloplasmin and factor VIII indicates that the location of glycosylation and bound metal ions, both of which are critical in domain association and stabilization, tend to overlap in some positions while diverging at others^[14].

Clinically, hemophilia A is characterized by factor VIII deficiency in clotting activity. That results to lengthy body fluid (blood) oozing after surgery, tooth extraction or surgery. It may also be characterized by recurring bleeding prior to a wound healing completely^[15]. Mutation is actually as a result of mutations in the factor 8 gene. Hemophilia A occurs when large inversion (gene rearrangement) occurs on a large segment of the F8 gene.

Approximately, 10%^[16] of hemophilia A carrier females recording having factor VIII clotting activity lower than 35% regardless of hemophilia A severity in their families. Bleeding severity may be more in those with low normal factor 8 activity.

 

 

 

Bibliography

Antonarakis, S. “Prenatal Diagnosis Of Haemophilia A By Factor Viii Gene Analysis.” The Lancet 325, no. 8443 (1999): 1407-409.

Azimifar, S. Babak, S. Yoosef Seyedna, and Sirous Zeinali. “Allele Frequencies of Three Factor VIII Gene Polymorphisms in Iranian Populations and Their Application in Hemophilia A Carrier Detection.” Am. J. Hematol. American Journal of Hematology 81, no. 5 (2006): 335-39.

Carcao, M. “Switching from Current Factor VIII (FVIII) to Longer Acting FVIII Concentrates – What Is the Real Potential Benefit?” Haemophilia 21, no. 3 (2015): 297-99.

Economou, Effrosini P., Haig H. Kazazian, and Stylianos E. Antonarakis. “Detection of Mutations in the Factor VIII Gene Using Single-stranded Conformational Polymorphism (SSCP).” Genomics 13, no. 3 (1992): 909-11.

Green, D. “Factor VIII Inhibitors: A 50-year Perspective.” Haemophilia 17, no. 6 (2011): 831-38.

Han, J.-Y., J.-N. Lee, S.-Y. Lee, I.-J. Kim, and C.-M Kim. “Identification of Factor VIII Gene Mutations and Carrier Detection in Korean Haemophilia A Patients.” Haemophilia 13, no. 3 (2007): 331-33.

Peerlinck, K., and C. Hermans. “Epidemiology of Inhibitor Formation with Recombinant Factor VIII Replacement Therapy.” Haemophilia 12, no. 6 (2006): 579-90.

 

^[1] Antonarakis, S. “Prenatal Diagnosis Of Haemophilia A By Factor Viii Gene Analysis.” The Lancet 325, no. 8443 (1999): 1407-409.

^[2] Antonarakis, S

^[3] Peerlinck, K., and C. Hermans. “Epidemiology of Inhibitor Formation with Recombinant Factor VIII Replacement Therapy.” Haemophilia 12, no. 6 (2006): 579-90.

^[4] Hermans

^[5] Han, J.-Y., J.-N. Lee, S.-Y. Lee, I.-J. Kim, and C.-M Kim. “Identification of Factor VIII Gene Mutations and Carrier Detection in Korean Haemophilia A Patients.” Haemophilia 13, no. 3 (2007): 331-33

^[6] Azimifar, S. Babak, S. Yoosef Seyedna, and Sirous Zeinali. “Allele Frequencies of Three Factor VIII Gene Polymorphisms in Iranian Populations and Their Application in Hemophilia A Carrier Detection.” Am. J. Hematol. American Journal of Hematology 81, no. 5 (2006): 335-39.

^[7] Economou, Effrosini P., Haig H. Kazazian, and Stylianos E. Antonarakis. “Detection of Mutations in the Factor VIII Gene Using Single-stranded Conformational Polymorphism (SSCP).” Genomics 13, no. 3 (1992): 909-11.

^[8] Antonarakis et al

^[9] Zeinali et al

^[10] Green, D. “Factor VIII Inhibitors: A 50-year Perspective.” Haemophilia 17, no. 6 (2011): 831-38.

^[11] Green

^[12] Carcao, M. “Switching from Current Factor VIII (FVIII) to Longer Acting FVIII Concentrates – What Is the Real Potential Benefit?” Haemophilia 21, no. 3 (2015): 297-99.

^[13] Zeinali et al

^[14] Hermans

^[15] Carcao

^[16] Green