The utility of hematopoietic stem cell karyotyping in the diagnosis of de novo myelodysplastic syndromes

Comparative Analysis of the Genetic Variants in Haematopoietic Stem/Progenitor and Mesenchymal Stem Cell Compartments in de novo Myelodysplastic Syndromes

Myelodysplastic Syndromes (MDS) are hematological clonal disorders. Bone marrow (BM) mesenchymal stem cells (MSCs) interact with the haematopoietic stem and progenitor cells (HSPCs) to regulate haematopoiesis. We studied the genetic variation profiles of BM derived CD34⁺ HSPCs and MSCs of same patient in a South Asian de novo MDS cohort with 20 patients. A total of 42 genes (variants 471) and 38 genes (variants 232) were mutated in HSPCs and MSCs respectively and majority (97%) were distinct variants. Variants included both known and novel, with variants predicted as pathogenic. In both cell types, most frequently mutated genes were TET2, KDM6A, BCOR, EZH2 and ASXL. DNA methylation and chromatin remodeling were shown to be affected in both cell types with a high frequency. RNA splicing was affected more in HSPCs. Gene variants in the cohesion complex and epigenetic mechanisms were shown to co-exist. We report variant profile of MSCs and CD34⁺ HSPCs from a South Asian cohort, with novel variants with potential for further study as biomarkers in MDS. Distinct variants confined to each cellular compartment indicate that the genetic variations occur following lineage commitment.

3D Telomere Structure Analysis to DetectGenomic Instability and Cytogenetic Evolutionin Myelodysplastic Syndromes

The disease course of myelodysplastic syndromes (MDS) features chromosome instability and clonal evolution, leading to the sequential acquisition of novel cytogenetic aberrations and the accumulation of these abnormalities in the bone marrow. Although clonal cytogenetic abnormalities can be detected by conventional cytogenetics in 50% of patients with MDS, such distinguishing patterns are lacking in the other 50%. Despite the increase in the prognostic value of some biomarkers, none of them is specific and able to discriminate between stable and unstable patients that subsequently progress to acute myeloid leukemia. This pilot study aimed to investigate the potential use of the 3D telomere profiling to detect genomic instability in MDS patients with or without clonal cytogenetic evolution. The comparison between different time points in patients with cytogenetic changes showed that in the CD34+ MDS cells, there was a significant decrease in the total number of telomeric signals, the average intensity of signals and the total intensity of telomeres. By contrast, the number of aggregates increased during cytogenetic evolution (p < 0.001). This pattern was observed only for MDS patients with cytogenetic evolution but was absent in patients without cytogenetic changes. In conclusion, we demonstrated that the 3D nuclear telomere organization was significantly altered during the MDS disease course, and may have contributed to cytogenetic clonal evolution.