Thromb Haemost 2018; 118(04): 709-722
DOI: 10.1055/s-0038-1637749
Cellular Haemostasis and Platelets
Schattauer GmbH Stuttgart

Genetic and Functional Characterization of ADAMTS13 Variants in a Patient Cohort with Upshaw–Schulman Syndrome Investigated in Germany

Wolf Achim Hassenpflug
1   Department of Paediatric Haematology and Oncology, University Medical Centre Hamburg-Eppendorf, Hamburg, Germany
,
Tobias Obser
1   Department of Paediatric Haematology and Oncology, University Medical Centre Hamburg-Eppendorf, Hamburg, Germany
,
Julia Bode
1   Department of Paediatric Haematology and Oncology, University Medical Centre Hamburg-Eppendorf, Hamburg, Germany
,
Florian Oyen
1   Department of Paediatric Haematology and Oncology, University Medical Centre Hamburg-Eppendorf, Hamburg, Germany
,
Ulrich Budde
2   Department of Haemostaseology, MEDILYS Laborgesellschaft mbH, Hamburg, Germany
,
Sonja Schneppenheim
2   Department of Haemostaseology, MEDILYS Laborgesellschaft mbH, Hamburg, Germany
,
Reinhard Schneppenheim
1   Department of Paediatric Haematology and Oncology, University Medical Centre Hamburg-Eppendorf, Hamburg, Germany
,
Maria Alexandra Brehm
1   Department of Paediatric Haematology and Oncology, University Medical Centre Hamburg-Eppendorf, Hamburg, Germany
› Author Affiliations
Further Information

Publication History

06 November 2017

14 January 2018

Publication Date:
19 March 2018 (online)

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Abstract

Upshaw–Schulman syndrome (USS) is caused by severe ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) deficiency due to homozygous or compound heterozygous mutations in the ADAMTS13 gene. Previous studies suggest three possible disease mechanisms: (1) reduced secretion of ADAMTS13 variants, (2) impaired proteolytic activity, (3) defective biosynthesis due to nonsense-mediated decay. Expression studies have failed to establish a clear genotype/phenotype correlation that could explain the significant variability in the age of onset and patients' clinical courses. In this study, we investigated ADAMTS13 sequence variations in 30 USS patients and identified 31 disease-causing mutations; among them 10 novel variants. While none of the recombinant proteins exhibited significant retention in the endoplasmic reticulum, secretion and activity analysis revealed defective release for all but one missense mutant. The latter exhibited normal secretion but impaired activity due to inactivation of the catalytic domain. Truncated mutants showed secretion and residual activity even though the patients suffered from a severe phenotype. The expression systems which we used may not be appropriate here, as they do not assess nonsense-mediated decay causing degradation of mRNA. In some patients, phenotypic severity could be explained by the combined effects of two mutations. Genetic screening in combination with in vitro characterization of ADAMTS13 variants from both alleles is a valuable tool to predict the phenotypic severity of USS. When necessary, supplementary methods, such as kinetics under flow conditions and mRNA processing assays, can be included. Such data are helpful to identify patients who are at high risk for severe attacks and therefore might benefit from prophylactic treatment.

Authors' Contributions

W.A.H. designed the study, analysed data, and edited and wrote parts of the manuscript. T.O., F.O., J.B., U.B. and S.S. performed experiments and analysed data. R.S. designed the outline of the study, analysed data and edited the manuscript. M.A.B. designed, performed and supervised experiments and wrote the manuscript.


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