Refining the roles of genetic, environmental, and endogenous factors in Factor VIII activity levels. Público

Viel, Kevin Roland (2007)

Permanent URL: https://etd.library.emory.edu/concern/etds/c534fp02h?locale=pt-BR
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Abstract

Background: Factor VIII (FVIII) is a central coagulation protein associated with hemophilia A at one end of the bleeding spectrum and thrombosis at the other end. A wide variety of factors are associated with increases in its activity, such as von Willebrand factor (VWF), exertion, mental stress, inflammation, diabetes, and overseas air travel, but not mutations within the structural gene, F8. Recently, an association between depression and FVIII:C level has been reported. Goals: The first goal of this dissertation was to characterize the genetic variations in F8 using 222 X chromosomes. The second was to determine if any of the variants are associated with FVIII:C levels, controlling for appropriate variables. We then attempted to replicate the association in a different population of unrelated white and black women. Finally, we investigated the role of depression as a possible non-genetic determinant of FVIII activity levels in these women. Results: We identified 47 genetic variants in F8, including five missense mutations (W0255C, R0484H, R0776G, D1241E, and M2238V) and five SNPs in the promoter region. Two SNPs (G056010A and C092714G, which encodes D1241E) were strongly associated with FVIII:C levels and, in this study of 21 families, were also in allelic association (r2 = 0.84, unadjusted). We replicated the association of C092714 and FVIII:C level within the white subjects of the second study, but in the black subjects the result was not strong and included the possibility of no association. Due to resource limitations, we were unable to genotype G056010A. Among the black women depression was suggestively associated with higher FVIII:C levels, whereas among white women it was not. Finally, though not the focus of these investigations, we raised the possibility that VWF antigen level and Factor IX activity level may not be just confounders, but also intermediates in a complex, unknown system of coordinate regulation.

Table of Contents

Chapter 1. Introduction

    I. Focus of the dissertation

    II. Overview of the biological process of coagulation

        A. Introduction

        B. Zymogen precursors

        C. Enzymatic coagulation cascade

        D. The role of platelets

        E. The importance of cofactors

        F. Attenuation, inactivation, clearance, and fibrinolysis

    III. Overview of the FVIII protein

        A. Introduction

        B. Structural organization

        C. Biosynthesis

        D. Post-translational modification

        E. Secretion

        F. Activation/Inactivation

        G. Clearance

    IV. Overview of measurement

        A. Introduction

        B. Antigen level

        C. Activity level

        D. Measurement variability

    V. Overview of the genic data

        A. Introduction

        B. Overview of the F8 structural gene

        C. Generating DNA sequence data

    VI. Family-based studies

        A. Introduction

        B. Identity by descent / Degree of relation

        C. Violations of Mendelian inheritance

        D. Heritability

        E. Linkage Analysis

    VII. Determinants of FVIII:C Levels

        A. Introduction

        B. Environmental

        C. Endogenous

    VIII. FVIII:C levels and thrombosis

     IX. Goals of the dissertation

 

Chapter 2. A sequence variation scan of the coagulation Factor VIII (FVIII) structural gene and associations with plasma FVIII activity levels.

    Abstract

    Introduction

    Patients, materials, and methods

    Results

    Discussion

    Acknowledgements

    Authorships

    References

 

Chapter 3. The C allele of the Factor VIII (F8) 092714 single nucleotide polymorphism is additively associated with increased Factor VIII activity levels in white women, but only weakly associated in black women.

 

    I.  Introduction

    II. Materials and Methods

        A. Study Population

        B.  Genotyping

        C.  Statistical Analysis

    III.  Results

        A.  Main Findings

        B.  Sensitivity Analyses

        C.  Additional Adjustments

    IV.  Discussion

    V.  Appendix

        A.  Possible Selection bias

        B.  Control of confounding

        C.  Influential observations

        D.  Confounders or potentially co-regulated factors

 

Chapter 4. The association between Depression and plasma Factor VIII activity (FVIII:C) levels in reproductive aged women

 

    I.  Introduction

    II. Materials and Methods

        A.  Study Population

        B.  CES-D instrument

        C.  Statistical Analysis.

    III.  Results

    IV.  Discussion

    V.  Appendix

        A.  Possible Selection bias

        B.  Impact of Adjustment for Factor IX and for VWF:Ag

 

Chapter 5. Conclusion

    I.  Goals, Brief Overview of Background, and Importance

        A. FVIII is central to proper hemostasis

        B.  Epidemiologic and Public Health Importance

    II.  Review of Major Findings       

        A.  Genetic Variation in F8

        B.  Association between F8 variants and FVIII:C level

        C.  Association between depression and FVIII:C level

        D.  New perspective on established covariates

    III.  Cohesion of results

        A.  Pre-requisite variant discovery

        B.  Replication is necessary

        C.  Adjustment for VWF:Ag and FIX:C level

        D.  Implication of replication

    IV. Agreement with current knowledge

        A.  The association between C092714G and FVIII:C levels was novel

  B.  Depression and FVIII:C levels

    V.  Important Strengths

    VI.  Important Weaknesses

   VII. Conclusions

        A.  FVIII has multiple forms

        B.  C092714G is associated with FVIII:C levels

        C.  The association between FVIII:C and depression was weakly supported

   VIII. Future directions

        A.  Measurement of FVIII:Ag levels

        B.  Characterizing the proteins with which FVIII interacts

        C.  Explore associations with haplotypes

        D.  The role of Depression

        E.  Refine the definition of diabetes

      

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