VPB0364 - Defective megakaryopoiesis in ETV6-variant carriers results from an aberrant megakaryocyte-erythroid progenitor population

Sunday, July 10, 2022

6:30 PM – 7:30 PM

Location: Exhibition

Presentation Format: Virtual

Presenting Author(s)

Timothée Jean-Rémi Bigot

PhD student
Aix Marseille Université
Marseille, Provence-Alpes-Cote d'Azur, France

Co-Author(s)

EG

Elisa Gabinaud

PhD student
Aix Marseille Université
Marseille, Provence-Alpes-Cote d'Azur, France
LH

Laurent Hannouche

Research Engineer
Aix Marseille Université
Marseille, Provence-Alpes-Cote d'Azur, France
VS

Véronique Sbarra

Assistant Engineer
Aix Marseille Université
Marseille, Provence-Alpes-Cote d'Azur, France
DP

Dominique Payet-Bornet

Research Director
CNRS
Marseille Cedex 9, Provence-Alpes-Cote d'Azur, France
ML

Marie Loosveld

MD, PhD
Aix Marseille Université
Marseille Cedex 9, Provence-Alpes-Cote d'Azur, France
DP

Delphine Potier

Tenured Researcher
CNRS
Marseille Cedex 9, Provence-Alpes-Cote d'Azur, France
MA

Marie-Christine Alessi, MD

MD, Professor, C2VN Head
Aix Marseille Université
Marseille, Provence-Alpes-Cote d'Azur, France
MP

Marjorie Poggi

MCF
Aix Marseille Université
Marseille, Provence-Alpes-Cote d'Azur, France

Background: Germline mutations in the ETV6 gene are responsible for a familial thrombocytopenia and leukemia predisposition. Although previous studies showed that ETV6 plays an important role in megakaryocyte (MK) maturation and platelet formation, the mechanisms by which ETV6 dysfunction promotes thrombocytopenia remain unclear.

Aims: To study the effect of ETV6 variations on the differentiation of hematopoietic-stem/progenitor-cells (HSPC) at a single cell level and discover changes mediating the differentiation defect.

Methods: Peripheral CD34+-cells were isolated from controls and patients carrying two different ETV6 variants (P214L localized in the central domain and F417LfsTer4 in the ETS domain) and differentiated in MK. F417LfsTer4 has never been reported. Transcriptomic profiles were analyzed by scRNA sequencing at day 6 and 11 of culture.

Results: The transcriptomic profile of the F417LfsTer4 and P214L ETV6 are similar, indicating that the same dysregulation is observed with both variations. The patients’ cells strongly differ from those of controls at each timepoint (Figure 1). ETV6 deficient condition is characterized by a higher proportion of HSPC (18±8.2 vs 3.9±0.6%) and megakaryocyte-erythroid progenitor (MEP, (50±6.7 vs 39±2.0%), a reduced proportion of megakaryocyte-progenitor/megakaryocyte (MKP/MK, 13±2.3 vs 38±1.8%) and a lack of platelets. Genes differentially expressed between genotypes were identified for each hematopoietic cell stage. The transcriptomic profile of HSPCs and GMPs overlapped between control and patient cells. Pathway analysis using gene ontology identified the onset of divergence at the CMP stage, particularly for genes involved in the "regulation of protein localization in the nucleus". Divergence intensifies at MEP and MkP/Mk (Figure 2) stages. Mitochondrial cellular metabolism (i.e. oxidative phosphorylation, respiratory electron transport chain, ATP synthesis) is the most significantly downregulated pathway in patients.

Conclusion(s): ETV6 mutations affect early hematopoiesis, at the level of the CMP/MEP transition, resulting in an aberrant MEP population and a defect in megakaryopoiesis. Studying mitochondrial cellular metabolism may represent an interesting target to investigate.