BARD1 germline variants induce haploinsufficiency and DNA repair defects in neuroblastoma
Menée à l'aide d'échantillons de neuroblastomes, d'échantillons de tissus sains et de xénogreffes de neuroblastomes sur des modèles murins, cette étude met en évidence un mécanisme par lequel des variants constitutionnels du gène BARD1 induisent une haplo-insuffisance et des anomalies au niveau de la réparation de l'ADN
Résumé en anglais
Background : High-risk neuroblastoma is a complex genetic disease that is lethal in over 50% of patients despite intense multimodal therapy. Through genome-wide association studies (GWAS) and next-generation sequencing (NGS), we have identified common single nucleotide polymorphisms (SNPs) and rare, pathogenic (P) or likely pathogenic (LP) germline loss-of-function (LOF) variants in BARD1 enriched in neuroblastoma patients. The functional implications of these findings remain poorly understood.
Methods : We correlated BARD1 genotype with expression in normal tissues and neuroblastomas, along with the burden of DNA damage in tumors. To validate the functional consequences of germline P-LP BARD1 variants, we used CRISPR/Cas9 to generate isogenic neuroblastoma (IMR-5) and control (RPE1) cellular models harboring heterozygous BARD1 LOF variants (R112*, R150*, E287fs, and Q564*) and quantified genomic instability in these cells via NGS and with functional assays measuring the efficiency of DNA repair.
Results : Both common and rare neuroblastoma associated BARD1 germline variants were significantly associated with lower levels of BARD1 mRNA and an increased burden of DNA damage. Using isogenic heterozygous BARD1 LOF variant cellular models, we functionally validated this association with inefficient DNA repair. BARD1 LOF variant isogenic cells exhibited reduced efficiency in repairing Cas9-induced DNA damage, ineffective RAD51 focus formation at DNA double-strand break sites, and enhanced sensitivity to cisplatin and poly-ADP ribose polymerase (PARP) inhibition both in vitro and in vivo.
Conclusions : Taken together, we demonstrate that germline BARD1 variants disrupt DNA repair fidelity. This is a fundamental molecular mechanism contributing to neuroblastoma initiation that may have important therapeutic implications.
