A self-repair history: compensatory effect of a de novo variant on the FANCA c.2778+83C>G splicing mutation

Autor: Ilaria Persico, Giorgia Fontana, Michela Faleschini, Melania Eva Zanchetta, Daniele Ammeti, Enrico Cappelli, Fabio Corsolini, Clara Mosa, Angela Guarina, Massimo Bogliolo, Jordi Surrallés, Carlo Dufour, Piero Farruggia, Anna Savoia, Roberta Bottega
Jazyk: angličtina
Rok vydání: 2023
Předmět:
Zdroj: Frontiers in Genetics, Vol 14 (2023)
Druh dokumentu: article
ISSN: 1664-8021
DOI: 10.3389/fgene.2023.1209138
Popis: Introduction: Fanconi anemia (FA) is a genome instability condition that drives somatic mosaicism in up to 25% of all patients, a phenomenon now acknowledged as a good prognostic factor. Herein, we describe the case of P1, a FA proband carrying a splicing variant, molecularly compensated by a de novo insertion.Methods and Results: Targeted next-generation sequencing on P1’s peripheral blood DNA detected the known FANCA c.2778 + 83C > G intronic mutation and suggested the presence of a large deletion on the other allele, which was then assessed by MLPA and RT-PCR. To determine the c.2778 + 83C > G splicing effect, we performed a RT-PCR on P1’s lymphoblastoid cell line (LCL) and on the LCL of another patient (P2) carrying the same variant. Although we confirmed the expected alternative spliced form with a partial intronic retention in P2, we detected no aberrant products in P1’s sample. Sequencing of P1’s LCL DNA allowed identification of the de novo c.2778 + 86insT variant, predicted to compensate 2778 + 83C > G impact. Albeit not found in P1’s bone marrow (BM) DNA, c.2778 + 86insT was detected in a second P1’s LCL established afterward, suggesting its occurrence at a low level in vivo. Minigene assay recapitulated the c.2778 + 83C > G effect on splicing and the compensatory role of c.2778 + 86insT in re-establishing the physiological mechanism. Accordingly, P1’s LCL under mitomycin C selection preserved the FA pathway activity in terms of FANCD2 monoubiquitination and cell survival.Discussion: Our findings prove the role of c.2778 + 86insT as a second-site variant capable of rescuing c.2778 + 83C > G pathogenicity in vitro, which might contribute to a slow hematopoietic deterioration and a mild hematologic evolution.
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