PB0994 - Intronic exploration of PROC in patients with unexplained protein C deficiencies.

Monday, June 26, 2023

18:30 – 19:30 ET

Room: Exhibition

Co-Author(s)

CR

Carla RIAL

Residency
Service d’Hématologie biologique, AP-HP, Hôpital européen Georges-Pompidou, F-75015, Université Paris Cité, Inserm, PARCC, F-75015 Paris, France
Paris, Ile-de-France, France

Co-Author(s)

SG

Sophie Gandrille

PharmD, PhD
Service d’Hématologie biologique, AP-HP, Hôpital européen Georges-Pompidou, F-75015, Université Paris Cité, Inserm U1140, F-75006 Paris, France
Paris, Ile-de-France, France
DH

Dominique HELLEY

MD, PhD
Service d’Hématologie biologique, AP-HP, Hôpital européen Georges-Pompidou, F-75015, Université Paris Cité, Inserm, PARCC, F-75015 Paris, France
Paris, Ile-de-France, France
IP

Isabelle PRESOT

Laboratory technician
Service d’Hématologie biologique, AP-HP, Hôpital européen Georges-Pompidou, F-75015
Paris, Ile-de-France, France
SB

Sébastien BERTIL

Laboratory engineer
Service d’Hématologie biologique, AP-HP, Hôpital européen Georges-Pompidou, F-75015
Paris, Ile-de-France, France

Presenting Author(s)

Philippe DE MAZANCOURT, MD, PhD

MD, PdD
Laboratoire de biologie moléculaire, AP-HP, Hôpital Ambroise Paré, F-92100, Université Paris Saclay, Inserm, UMR 1179, F-92100 Boulogne-Billancourt, France
Boulogne-Billancourt, Ile-de-France, France

Co-Author(s)

Laetitia Mauge, PharmD PhD

PharmD, PhD
Service d’Hématologie biologique, AP-HP, Hôpital européen Georges-Pompidou, F-75015, Université Paris Cité, Inserm, PARCC, F-75015 Paris, France
Paris, Ile-de-France, France

Background: Inherited protein C deficiency (PCD) is associated with a 7-fold risk of first venous thromboembolism (VTE). More than 300 exonic and flanking variants of protein C (PC) coding gene, PROC, impacting PC function or synthesis, have been described (Human gene mutation database). However, PCD remains genetically unexplained in 5-10% of patients.

Aims: To study PROC introns in patients with PCD not explained by exonic or flanking variants or variants in the 5’-, 3’-UTR or gene promoter.

Methods: This retrospective study included patients with PC clot activity below 70% not explained by conditions inducing acquired PCD (abnormal hepatic function, coagulation activation), interferences (FV Leiden, high FVIII level), variant in PROC exonic or flanking regions (including the first 30 nucleotides) or variant in the 5’-, 3’-UTR or gene promoter region. All patients gave informed consent to genetic exploration of PCD. NGS using Illumina Technology was performed with a MiSeq sequencer and bioinformatic analysis with Polydiag. Pathogenicity was predicted using ACMG recommendations and Fruitfly, SpliceAI, NetGene, Exon-Skipping and RNAfold softwares.

Results: PROC gene was analyzed with NGS in 53 patients (39, IQR[28.5-48] years old; 36% men; 58% IQR[44-62] PC clot activity), 64% of them had a personal history of VTE. We found class 3 intronic variants for 9 patients. Among them, 6 had an intronic variant that could induce a possible change in splicing either by creating acceptor/donor site (3 variants in 4 patients) or by modifying RNA secondary structure (2 variants).

Conclusion(s): We report here 5 intronic variants in 6 patients that could explain PCD. A segregation study in family members if available or a functional study by minigen assay is necessary to confirm the pathogenicity of these variants. Intronic exploration of PROC can be proposed in severe PCD not explained by exonic and flanking region analysis.