Page 254 - Haematologica Vol. 107 - September 2022

LETTER TO THE EDITOR
mutants alone (Figure 3C), confirming that M-ETV6 antag- onizes the repression activity of WT-ETV6. For all the mu- tations tested, we observed a slight increment of the repression activity, which could be explained by formation of WT/WT functionally active homodimers.
In summary, we show that all but two of the variants identified are pathogenic. Indeed, their respective mutant transcription factors do not enter the nucleus to exert their repressive activity. Moreover, inhibiting the protein nuclear export, we fully demonstrated that there is no trafficking of the mutant transcription factor between cytoplasm and nucleus, further supporting the hypothesis that M-ETV6 are unable to translocate to the nucleus.
In addition, we demonstrate and extend the dominant negative effect of ETV6 mutations described to date2,3,9 to other mutations (Q347P, W380R and R396G), suggesting that this is a common pathogenic mechanism of the dis- ease.
These results increase our knowledge on the molecular basis of ETV6-RT and allow us to correctly classify vari- ants to provide a definitive molecular diagnosis to pa- tients and their families.
Since ETV6-RT is associated with an increased risk to de- velop hematological malignancies as supported also by identification of ETV6 germline mutations in patients af- fected by leukemia,3–5,9 correct molecular diagnosis would allow us to better understand this disease and to evaluate additional risks for patients. Moreover, improving our knowledge on pathogenic mechanisms is of fundamental importance to develop therapeutic strategies. Since M- ETV6 is unable to enter the nucleus, as fully demon- strated by the leptomycin B treatment, we should develop approaches leading to "release" the WT form of ETV6, for instance silencing the mutated transcript and/or prevent- ing the dimerization of the WT and mutated forms of the transcription factor.
Authors
Michela Faleschini,1 Daniele Ammeti,1 Nicole Papa,2 Caterina Alfano,3 Roberta Bottega,1 Giorgia Fontana,1 Valeria Capaci,2 Melania E. Zanchetta,1 Federico Pozzani,4 Francesca Montanari,5 Valeria Petroni,6 Paola Giordano,7 Patrizia Noris,8 Fiorina Giona9 and Anna Savoia1,2
1Istitute for Maternal and Child Health – IRCCS Burlo Garofolo, Trieste; 2Department of Medical Sciences, University of Trieste,
References
1. Galera P, Dulau-Florea A, Calvo KR. Inherited thrombocytopenia and platelet disorders with germline predisposition to myeloid
Trieste; 3Structural Biology and Biophysics Unit, Fondazione Ri.MED, Palermo; 4Department of Life Sciences, University of Trieste, Trieste; 5Sant’Orsola-Malpighi University Hospital, Medical Genetics Unit, Bologna; 6SOSD Pediatric Oncohematology, University Hospital “Ospedali Riuniti”, Ancona; 7Interdisciplinary department of Medicine, Pediatric Unit, University “A.Moro” of Bari, Bari; 8Department of Internal Medicine, IRCCS Policlinico San Matteo Foundation, University of Pavia, Pavia and 9Department of Translational and Precision Medicine, Sapienza University of Rome, Rome, Italy
Correspondence:
A. SAVOIA - anna.savoia@burlo.trieste.it.
https://doi.org/10.3324/haematol.2022.280729
Received: February 4, 2022. Accepted: May 10, 2022. Prepublished: May 19, 2022.
©2022 Ferrata Storti Foundation Published under a CC BY-NC license
Disclosures
No conflicts of interest to disclose.
Contributions
MF and AS designed the study; MF and DA performed research and analysed data; NP and FP performed luciferase assays; AC performed structural analysis; RB and GF performed mutational screenings; VC and MEZ performed immunofluorescence assays; FM, VP, PG, PN and FG enrolled the patients; FM, DA and AS wrote the manuscript. All authors read and approved the manuscript.
Acknowledgments
We thank Professor Walter H.A. Khar for providing the lentiviral vector from which we cloned the wild-type full-length ETV6 cDNA.
Funding
This study was supported by IRCCS “Burlo Garofolo” (Ricerca Corrente 01/2018), AIRC Grant IG-21974 and IRCCS Policlinico San Matteo Foundation (Ricerca corrente 2018 intramural research grant to NP).
Data-sharing statement
All data relevant to the study are included in the manuscript and are available upon request to the corresponding author.
neoplasia. Int Lab Hematol. 2019;41(S1):131-141.
2. Noetzli L, Lo RW, Lee-Sherick AB, et al. Germline mutations in
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