Two SERPINC1 variants affecting N-glycosylation of Asn224 cause severe thrombophilia not detected by functional assays - Aix-Marseille Université Access content directly
Journal Articles Blood Year : 2022

Two SERPINC1 variants affecting N-glycosylation of Asn224 cause severe thrombophilia not detected by functional assays

Maria Eugenia de la Morena-Barrio
Eva Marie Jacobsen
  • Function : Author
Nina Iversen
  • Function : Author
Antonia Miñano
  • Function : Author
Belén de la Morena-Barrio
Carlos Bravo-Pérez
Jose Padilla
Rosa Cifuentes
  • Function : Author
Susana Asenjo
Jean François Deleuze
  • Function : Author
David Alexandre Trégouët
Maria Luisa Lozano
Vicente Vicente
Per Morten Sandset
Javier Corral

Abstract

Abstract Antithrombin deficiency, the most severe congenital thrombophilia, might be underestimated, as some pathogenic variants are not detected by routine functional methods. We have identified 2 new SERPINC1 variants, p.Glu227Lys and p.Asn224His, in 4 unrelated thrombophilic patients with early and recurrent thrombosis that had normal antithrombin activity. In one case, the mutation was identified by whole genome sequencing, while in the 3 remaining cases, the mutation was identified by sequencing SERPINC1 based on a single functional positive finding supporting deficiency. The 2 variants shared a common functional defect, an impaired or null N-glycosylation of Asn224 according to a eukaryotic expression model. Carriers had normal anti-FXa or anti-FIIa activities but impaired anti-FVIIa activity and a detectable loss of inhibitory function when incubating the plasma for 1 hour at 41°C. Moreover, the β glycoform of the variants, lacking 2 N-glycans, had reduced secretion, increased heparin affinity, no inhibitory activity, and a potential dominant–negative effect. These results explain the increased thrombin generation observed in carriers. Mutation experiments reflected the role that Lysine residues close to the N-glycosylation sequon have in impairing the efficacy of N-glycosylation. Our study shows new elements involved in the regulation of N-glycosylation, a key posttranslational modification that, according to our results, affects folding, secretion, and function, providing new evidence of the pathogenic consequence of an incorrect N-glycosylation of antithrombin. This study supports that antithrombin deficiency is underestimated and encourages the development of new functional and genetic tests to diagnose this severe thrombophilia.

Dates and versions

hal-03800816 , version 1 (06-10-2022)

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Maria Eugenia de la Morena-Barrio, Pierre Suchon, Eva Marie Jacobsen, Nina Iversen, Antonia Miñano, et al.. Two SERPINC1 variants affecting N-glycosylation of Asn224 cause severe thrombophilia not detected by functional assays. Blood, 2022, 140 (2), pp.140-151. ⟨10.1182/blood.2021014708⟩. ⟨hal-03800816⟩
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