TY - JOUR
T1 - Antithrombin p.Thr147Ala
T2 - The First Founder Mutation in People of African Origin Responsible for Inherited Antithrombin Deficiency
AU - Orlando, Christelle
AU - de la Morena-Barrio, Belén
AU - Pareyn, Inge
AU - Vanhoorelbeke, Karen
AU - Martínez-Martínez, Irene
AU - Vicente, Vicente
AU - Corral, Javier
AU - Jochmans, Kristin
AU - de la Morena-Barrio, Maria Eugenia
N1 - Georg Thieme Verlag KG Stuttgart · New York.
PY - 2021/2/1
Y1 - 2021/2/1
N2 - BACKGROUND: Hereditary antithrombin deficiency is a rare autosomal-dominant disorder predisposing to recurrent venous thromboembolism (VTE). To date, only two founder mutations have been described.OBJECTIVES: We investigated the antithrombin p.Thr147Ala variant, found in 12 patients of African origin. This variant is known as rs2227606 with minor allele frequency of 0.5% in Africans and absent in Europeans. A possible founder effect was investigated.METHODS: Phenotypical characterization was established through immunological and functional methods, both under basal and stress conditions. Recombinant antithrombin molecules were constructed by site-directed mutagenesis and expressed in HEK-293T cells. Secreted antithrombin was purified and functionally characterized. Structural modeling was performed to predict the impact of the mutation on protein structure. A novel nanopore sequencing approach was used for haplotype investigation.RESULTS: Ten patients experienced VTE, stroke, or obstetric complications. Antithrombin antigen levels and anti-IIa activity were normal or slightly reduced while anti-Xa activity was reduced with only one commercial assay. On crossed immunoelectrophoresis, an increase of antithrombin fractions with reduced heparin affinity was observed under high ionic strength conditions but not under physiological conditions. The recombinant p.Thr147Ala protein displayed a reduced anti-Xa activity. Structural modeling revealed that residue Thr147 forms three hydrogen bonds that are abolished when mutated to alanine. The investigated patients shared a common haplotype involving 13 SERPINC1 intragenic single nucleotide polymorphisms.CONCLUSION: Antithrombin p.Thr147Ala, responsible for antithrombin type II heparin binding site deficiency, is the first founder mutation reported in people of African ancestry. This study further emphasizes the limitations of commercial methods to diagnose this specific subtype.
AB - BACKGROUND: Hereditary antithrombin deficiency is a rare autosomal-dominant disorder predisposing to recurrent venous thromboembolism (VTE). To date, only two founder mutations have been described.OBJECTIVES: We investigated the antithrombin p.Thr147Ala variant, found in 12 patients of African origin. This variant is known as rs2227606 with minor allele frequency of 0.5% in Africans and absent in Europeans. A possible founder effect was investigated.METHODS: Phenotypical characterization was established through immunological and functional methods, both under basal and stress conditions. Recombinant antithrombin molecules were constructed by site-directed mutagenesis and expressed in HEK-293T cells. Secreted antithrombin was purified and functionally characterized. Structural modeling was performed to predict the impact of the mutation on protein structure. A novel nanopore sequencing approach was used for haplotype investigation.RESULTS: Ten patients experienced VTE, stroke, or obstetric complications. Antithrombin antigen levels and anti-IIa activity were normal or slightly reduced while anti-Xa activity was reduced with only one commercial assay. On crossed immunoelectrophoresis, an increase of antithrombin fractions with reduced heparin affinity was observed under high ionic strength conditions but not under physiological conditions. The recombinant p.Thr147Ala protein displayed a reduced anti-Xa activity. Structural modeling revealed that residue Thr147 forms three hydrogen bonds that are abolished when mutated to alanine. The investigated patients shared a common haplotype involving 13 SERPINC1 intragenic single nucleotide polymorphisms.CONCLUSION: Antithrombin p.Thr147Ala, responsible for antithrombin type II heparin binding site deficiency, is the first founder mutation reported in people of African ancestry. This study further emphasizes the limitations of commercial methods to diagnose this specific subtype.
KW - Antithrombin p.Thr147Ala
KW - Mutation
KW - African Origin
KW - Inherited Antithrombin Deficiency
UR - http://www.scopus.com/inward/record.url?scp=85091775921&partnerID=8YFLogxK
U2 - 10.1055/s-0040-1716531
DO - 10.1055/s-0040-1716531
M3 - Article
C2 - 32920809
VL - 121
SP - 182
EP - 191
JO - Thrombosis and Haemostasis
JF - Thrombosis and Haemostasis
SN - 0340-6245
IS - 2
ER -