OC 75.4 - Unraveling the molecular base of FXI deficiency in 96 unrelated Caucasian patients by short- and long-read based sequencing methods: biochemical, functional and clinical consequences

Wednesday, June 28, 2023

11:00 – 11:15 ET

Room: 510

Session Available As: On-Demand

Co-Author(s)

JR

Juan Jose Rojo-Carrillo

Predoctoral fellow
Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Pascual Parrilla, CIBERER, Murcia, Spain
Murcia, Murcia, Spain
Belen de la morena-Barrio, PhD

Postdoctoral fellow
Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Pascual Parrilla, CIBERER, Murcia, Spain
murcia, Murcia, Spain
CB

Carlos Bravo-Perez

Postdoctoral fellow
Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Pascual Parrilla, CIBERER, Murcia, Spain
Murcia, Murcia, Spain
AM

Antonia Miñano

Technician
Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Pascual Parrilla, CIBERER, Murcia, Spain
Murcia, Murcia, Spain
JP

Jose Padilla

Technician
Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Pascual Parrilla, CIBERER, Murcia, Spain
Murcia, Murcia, Spain
RC

Rosa Cifuentes

Predoctoral fellow
Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Pascual Parrilla, CIBERER, Murcia, Spain
Murcia, Murcia, Spain
�P

Ángeles Palomo Bravo

Hematologist
Hematology Service, Hospital Materno-Infantil de Málaga, Málaga, Spain.
Malaga, Andalucia, Spain
VV

Vicente Vicente

Researcher and Medical Doctor
Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Pascual Parrilla, CIBERER, Murcia, Spain
Murcia, Murcia, Spain
ML

María Luisa Lozano

Leader of Hematology Service in Murcia
Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Pascual Parrilla, CIBERER, Murcia, Spain
Murcia, Murcia, Spain
Javier Corral, PhD

PhD
Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Pascual Parrilla, CIBERER, Murcia, Spain
Murcia, Murcia, Spain

Presenting Author(s)

Maria Eugenia de la Morena-Barrio, PhD

Reseacher
Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Arrixaca, CIBERER, Murcia, Spain
Murcia, Murcia, Spain

Background: FXI deficiency (FXID), considered rare in Caucasians, increases the risk of bleeding and protects against thrombosis. The characterization of new F11 genetic defects may allow identifying a) new mechanisms involved in this disorder, 2) domains and residues playing a role in folding, secretion, dimerization, or function of FXI, 3) the natural history of FXID.

Aims: To identify and characterize new genetic defects causing FXID

Methods: F11 was sequenced by NGS in 96 unrelated Caucasian families with FXID. Gross gene defects (SVs) were characterized by long-read sequencing. Plasma FXI was studied by functional and immunological methods with or without activation by silica. Recombinant expression of FXI was performed in HEK293.

Results: Thirty-one different F11 variants were identified (Figure 1). Two duplications and one deletion were characterized at nucleotide resolution. Six missense variants caused CRM+ deficiency, including the first one in Apple-3 domain, 3 in the catalytic domain and 2 disrupting disulfide bridges: p.Phe295Cys, found in hemizygosis in a patient with FXI:C=4%, that produced, also in the recombinant model, two different dimers through a potential shuffling of disulfide bonds; and p.Cys339Phe, found in heterozygosis in 2 unrelated subjects with mild FXID, that had circulating monomers activated by silica. Interestingly, in vitro WT-F11 expression secreted similar rates of dimer and monomer (Figure 2).
Most FXID cases did not have or had only mild bleeding events, although the carrier of p.Arg268His (CRM+, FXI:C=50%) died from a severe hemorrhage during COVID-19 infection.

Conclusion(s): We confirm a large genetic heterogeneity of FXID in Caucasians. SVs affecting F11, probably caused by recombination of repetitive elements, are heterogeneous and may not be detected by short-read sequencing. Most F11 variants cause CRM- defects, but we identified 6 CRM+ deficiencies, including the first one producing FXI monomers in plasma, that supports the relevance of Cys339 in the removal of WT monomers from circulation. PI21/00137;PMP21/00052

Learning Objectives:

Describe the importance of identifying structural variants in F11 gene causing FXID and explain how long-read sequencing was used to characterize them.
Describe the significance of FXI cross reactive material + deficiencies and the relevance this type of FXI deficiency to understand the folding and function of FXI by using examples identified in this study such as p.Phe295Cys and p.Cys339Phe
Demonstrate the genetic heterogeneity of FXI deficiency in Caucasians and discuss the possibility that this disorder is understimated