Summary
Type 2M von Willebrand disease (VWD) refers to variants with decreased platelet-dependent
function that is not associated with the loss of high molecular weight (HMW) von Willebrand
factor (VWF) multimers. This category includes the so-called “phenotype B” responsible
for inexistent ristocetin-induced but normal botrocetin-induced binding of VWF to
platelet glycoprotein Ib. The missense mutation G1324S was identified in the first
patient reported to display “phenotype B”.
We report here on the identification in four members of a French family of a missense
mutation also affecting this glycine residue but changing it into an alanine residue.
These individuals are heterozygous for this mutation and two of them display an additional
quantitative VWF deficiency resulting from a stop codon at position 2470. After transient
transfection in Cos-7 cells, the mutated recombinant protein harbouring the G1324A
substitution was shown to exhibit normal multimers and inexistent ristocetin-induced
but normal botrocetininduced binding to GPIb, confirming the classification of this
new mutation as a type 2M VWD mutation.
Keywords
von Willebrand factor - von Willebrand disease - mutation - recombinant protein -
Cos-7 cells