Expression Analysis of dic(1;7)(q10;p10) in Myelodysplastic Syndromes (MDS) compared to control cohort and therapy-related Myeloid Neoplasms (t-MN)

The unbalanced translocation t(1;7)(q10;p10), generating 1q trisomy and 7q monosomy, is due to centromere-centromere juxtaposition. This dicentric chromosome is a recurrent change in myelodysplastic syndromes (MDS), with half the cases arising after chemo/radio-therapy. To date, given the absence of genes within the centromeric regions, no specific molecular events have been identified in this cytogenetic subgroup. We first identified a comprehensive genetic and epigenetic landscape of MDS with dic(1;7)(q10;p10) and compared it to normal controls and other therapy-related Myeloid Neoplasms (t-MNs). RNA-seq showed a unique downregulated signature in dic(1;7) cases, affecting more than 80% of differentially expressed genes. As revealed by pathway and gene ontology analyses, downregulation of ATP-binding cassette (ABC) transporters and of genes related to lipid metabolism, and upregulation of p53 signaling were the most relevant biological features of dicentric-positive MDS. Despite 1q trisomy, more than 50% of 1q deregulated genes were downregulated. This partial gene dosage effect was clarified by epigenetic analysis, which highlighted the presence of a specific hypermethylated pattern on 1q. Furthermore, in a supervised analysis, hypermethylation in all dicentrics clustered at intronic enhancers and was enriched for Krüppel-like transcription factors binding sites. Low expression levels of enhancer putative target genes accounted for more than 30% of the downregulated signature. Our findings demonstrate that alteration of centromeric DNA in dic(1;7) cases imposes a specific transcriptional program, driven by a unique epigenomic signature. Overall design: mRNA profiles of 5 dic(1;7)(q10;p10) cases, 4 controls (bone marrow samples from non-neoplastic cytopenias, normal bone marrow morphology and normal karyotype), and 5 therapy-related Myeloid Neoplasms (t-MNs) cases.