Molecular Genetics in the Von Willebrand disease Ghasem Rastegarlari

VON WILLEBRAND DISEASE VWD General definitions The most frequent congenital bleeding disorder caused by defects of VWF: - quantitative = Types 1 & 3 VWD - qualitative = Type 2 VWD Autosomal dominant/recessive pattern Women are more symptomatic

Von Willebrand disease Genetic aspect Human VWF Gene 178 kb, 52 exons mRNA 8.7 kb VWF (12p13.3) q p Chromosome

VWF gene in Chromosome 12 ENCODING REGIONS OF VWF AND FUNCTIONAL DOMAINS

PLATELET GPIb  A1 C A2 A3 SUBENDOTHELIUM COLLAGEN ADHESION ACTIVITIES OF VWF Collagen Heparin Sulphatide VWF:RCo VWF:CB A3 VWF:CP

6 Single Platelets Adherent to Endothelial Monolayer A.J. Reininger

7 Platelet Aggregate Adherent to Endothelial Monolayer A.J. Reininger

MOLECULAR MARKERS of Type 3 VWD Complete deficiency of VWF (VWF:Ag < 1) Autosomal recessive pattern of inheritance Rare (1- 5 per million) but severe disorder Caused by several defects: gene deletions, frameshift-nonsense-missense-splite site mutations, defects of mRNA expression

Type 2A, 2B and 2M variants with decreased platelet-dependent function Autosomal dominant Can be caused mainly by missense mutations (small deletions or frameshift mutations also ) CLINICAL & MOLECULAR MARKERS of Type 2 VWD

CLINICAL & MOLECULAR MARKERS of Type 2N VWD Variants with markedly decreased affinity for factor VIII (FVIII) Inherited by recessive patterns Caused by missense mutations

Inheritance (autosomal dominant) BUT: Factors which can modify VWF levels: Sex (females may exhibit greater variability) Age (VWF higher in older individuals) Exercise and stress (VWF increases) ) Blood Group O (lower VWF levels ) CLINICAL & MOLECULAR MARKERS Type 1 VWD

Von Willebrand disease Genetic aspect It is important to determine the causative defect of VWF gene: to prove phenotypic diagnosis or to make a definite diagnosis of VWD when the phenotypic diagnosis is uncertain, Prenatal diagnosis Direct sequencing of the VWF gene

Conclusion (1) We have investigated 121 unrelated VWD patients 66 unrelated type 2 VWD patients 50 unrelated type 3 VWD B patients The molecular defects have been found in 109 patients with a detection rate of ~ 90% Nineteen novel mutations (not previously reported, in the International VWD mutation databases).

Identified mutations in VWD patients allowed direct carrier diagnosis and prenatal diagnosis Mutation analysis is now routinely carried out and is used as a first line method for carrier detection and will be used for prenatal diagnosis. All molecular analysis from the DNA extraction to sequencing were done in our Iranian Comprehensive Hemophilia Treatment Center Conclusion (2)