OC 78.5 - Exploring hidden bleeding phenotypes by screening FXIII and Fibrinogen genes

Wednesday, July 13, 2022

11:15 AM – 11:30 AM

Location: ExCel Center, ICC Capital Suite Room 1

Presentation Format: In-Person

Presenting Author(s)

SS

Sneha Singh, M.Sc, PhD

Post Doctoral Researcher
Uniklinikum Bonn
Bonn, Nordrhein-Westfalen, Germany

Co-Author(s)

NM

Nadia Mir-Montazeri

Physician
Uniklinikum Bonn
Bonn, Nordrhein-Westfalen, Germany
MJ

Muhammad Ahmer Jamil

Dr
Institute of Experimental Haematology and Transfusion Medicine and Center for Rare Diseases, University Hospital Bonn, Bonn, Germany
bonn, Nordrhein-Westfalen, Germany
Behnaz Pezeshkpoor

Group Leader
University Clinic Bonn AöR, Institute of Experimental Haematology and Transfusion Medicine, Bonn, Germany
Bonn, Nordrhein-Westfalen, Germany
Amit Sharma, PhD

Post Doctoral Researcher
All India Institute of Medical Sciences
New Delhi, Delhi, India
jD

johannes Dodt

Wissenschaftler
Paul-Ehrich institute
Langen, Hessen, Germany
PV

Peter Volkers

Wissenschaftler
Paul-Ehrich institute
Langen, Hessen, Germany
EH

Emma Hethershaw

Research Scientist
Unversity of Leeds
Leeds, England, United Kingdom
Helen Philippou, PhD

Professor
University of Leeds.
Leeds, England, United Kingdom
VI

Vytautas Ivaskevicius

Physician
Uniklinikum bonn
Bonn, Nordrhein-Westfalen, Germany
Johannes Oldenburg

Professor, Chairman and Director
University Clinic Bonn AöR, Institute of Experimental Haematology and Transfusion Medicine, Bonn, Germany
Bonn, Nordrhein-Westfalen, Germany
Arijit Biswas, PD Dr (Biol)

Scientist
Institute of Experimental Haematology and Transfusion Medicine, University Clinic Bonn
Bonn, Nordrhein-Westfalen, Germany

Background: The collaborative functional status of products encoded by Factor XIII (FXIII) and Fibrinogen genes, define the clot architecture in an individual. Genetic variations that even mildly influence either of the FXIII or Fibrinogen integrity at levels ranging from expression to complex assemblies; affects the integrity and functionality of fibrin clot.

Aims: This study aims to address the milder form of inherited heterozygous FXIII deficiency (FXIII plasma levels 20-60%) and to understand its genetic and clinical burden.

Methods: Sample Collection: Blood samples corresponding to apparently healthy controls [n=752 (unbiased cohort)] were collected at the University Clinic Bonn, Germany (Figure 1). Additionally, another group of sample of patients with suspected mild FXIII deficiency referred to the outpatient department of our hemophilia center were also collected (biased-control cohort).
Genetic characterization: DNA extracted from whole blood was analysed by NGS using Illumina based custom kits. Extracted plasma was tested for FXIII/Fibrinogen functional status using photometric assay, alpha-2-anti-plasmin incorporation assay, Pentylamine incorporation assay in-house FXIII antigenic ELISA and Fibrinogen activity.

Results: FXIII activity levels show good correlation with FXIII antigen, Fibrinogen and amongst different FXIIII activity assays. NGS analysis showed multiple heterozygous missense variants in F13A1 (43), F13B (23), FGA (26), FGB (4) and FGG (11) genes. In silico evaluations of heterozygous missense variants suggest that some of them could disrupt dimeric or heteromeric assembly of the complex. The cysteines of F13B gene appear to be mutational hotspots for mild FXIII deficiency.

Conclusion(s): There is a large inter-individual variability in circulating plasma FXIII levels (35-150%), with 6 individuals out of 752 with mild FXIII deficiency (prevalence: 0.8%) which is much higher than the theoretical estimate of 0.1%. In silico analysis suggests that the heterozygous missense variants largely affects the complex assembly of FXIII in plasma.