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Characterization of VWF gene conversions causing von Willebrand disease
Author(s) -
Ahmad Firdos,
Kannan Meganathan,
Obser Tobias,
Budde Ulrich,
Schneppenheim Sonja,
Saxena Renu,
Schneppenheim Reinhard
Publication year - 2019
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1111/bjh.15709
Subject(s) - von willebrand factor , von willebrand disease , missense mutation , mutant , gene , genetics , recombinant dna , glycoprotein , mutation , biology , microbiology and biotechnology , platelet , immunology
Summary We previously reported that von Willebrand Factor gene ( VWF ) conversions are a relatively frequent cause of von Willebrand disease ( VWD ), however, their molecular pathomechanisms resulting in variant phenotypes is largely unknown. Here, we characterized VWF conversions harbouring missense and synonymous mutations, through generating a series of mutant constructs followed by transient expression in 293 cells, and qualitative and quantitative analysis of recombinant VWF ( rVWF ). The characterization of mutant rVWF showed the critical roles of synonymous variants in the pathogenicity of VWF conversions. The gene conversion variants p.Val1229Gly, p.Asn1231Thr, p.Asn1231Ser and p.Ala1464Pro in the absence of synonymous p.Ser1263= and p.Gln1449= showed minimal effect on rVWF synthesis and activity. Interestingly, a construct including the synonymous variants displayed significantly low rVWF expression and activity. The variant p.Pro1266Leu showed gain of rVWF function toward glycoprotein Ibα; surprisingly, this function was significantly abolished in the presence of gene conversion variants p.Val1229Gly‐p.Asn1231Thr. Taken together, our expression studies suggest that synonymous variants in the combination of other gene conversion variants suppress the protein expression, possibly due to defective primary mRNA structure or processing. The variants p.Val1229Gly‐p.Asn1231Thr affected the VWF gain of function caused by variant p.Pro1266Leu, probably due to conformational changes in VWF.