Molecular Genetics in the Von Willebrand disease

Ghasem Rastegarlari

VON WILLEBRAND DISEASEVWD 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 diseaseGenetic aspect

Human VWF Gene

178 kb, 52 exonsmRNA 8.7 kb

VWF(12p13.3)

q

p

Chromosome 121 7 14 52

VWF gene in Chromosome 12

5’ 3’3728167

bp 0 1000 2000 3000 4000 5000 6000 7000 8000 9000

B1B2

B3

D1 D2 D’ D3 A1 A2 A3 D4 C1 C2 COOHH2N

RGD

IIb3

FVIII Platelets Endothelial cells

CK

MultimersS-S

DimersS-S1-23 163 2813

ENCODING REGIONS OF VWFAND FUNCTIONAL DOMAINS

PLATELETGPIb

A1

C C C CA2

A3

SUBENDOTHELIUM COLLAGEN

ADHESION ACTIVITIES OF VWF

CollagenHeparinSulphatide

VWF:RCo

VWF:CBA3

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 diseaseGenetic 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)