Transcriptional regulation of HSCs in Aging and MDS reveals DDIT3 as a Potential Driver of Dyserythropoiesis

Abstract

Myelodysplastic syndromes (MDS) are clonal hematopoietic stem cell (HSC) malignancies characterized by ineffective hematopoiesis with increased incidence in elderly individuals. Genetic alterations do not fully explain the molecular pathogenesis of the disease, indicating that other types of lesions may play a role in its development. In this work, we analyzed the transcriptional lesions of human HSCs, demonstrating how aging and MDS are characterized by a complex transcriptional rewiring that manifests as diverse linear and non-linear transcriptional dynamisms. While aging-associated lesions seemed to predispose elderly HSCs to myeloid transformation, disease-specific alterations may be involved in triggering MDS development. Among MDS-specific lesions, we detected the overexpression of the transcription factor DDIT3. Exogenous upregulation of DDIT3 in human healthy HSCs induced an MDS-like transcriptional state, and a delay in erythropoiesis, with an accumulation of cells in early stages of erythroid differentiation, as determined by single-cell RNA-sequencing. Increased DDIT3 expression was associated with downregulation of transcription factors required for normal erythropoiesis, such as KLF1, TAL1 or SOX6, and with a failure in the activation of their erythroid transcriptional programs. Finally, DDIT3 knockdown in CD34+ cells from MDS patients was able to restore erythropoiesis, as demonstrated by immunophenotypic and transcriptional profiling. These results demonstrate that DDIT3 may be a driver of MDS transformation, and a potential therapeutic target to restore the inefficient erythropoiesis characterizing these patients.

Germline ERCC excision repair 6 like 2 (ERCC6L2) mutations lead to impaired erythropoiesis and reshaping of the bone marrow microenvironment

“…To substantiate our findings, we generated RNA‐sequencing data from ERCC6L2 ‐deficient erythroid‐committed HSPCs and used an in silico approach to infer cell abundance at various stages of differentiation within our populations. Based on gene signatures derived from single‐cell RNA‐sequencing analysis of erythroid subtypes, 10 , 11 we performed CIBERSORTx deconvolution on our bulk RNA‐sequencing data sets. Our analysis revealed that ERCC6L2‐ KD and patient erythroid cells had higher proportions of polychromatic erythroblasts compared to Scramble (61.5% and 36.6% respectively), which were enriched instead for more mature subtypes, orthochromatic erythroblasts (39.4%) or reticulocytes (32.6%) (Figure 4A ; Figure S5A ).…”

Targeting the EIF2AK1 Signaling Pathway Rescues Red Blood Cell Production in SF3B1-Mutant Myelodysplastic Syndromes With Ringed Sideroblasts

“…The EIF2AK1 effector DDIT3 is overexpressed in SF3B1 WT MDS HSCs ( 38 ). DDIT3 overexpression delays the erythroid differentiation of MDS CD34 + cells by affecting the activation of erythroid transcriptional programs.…”

“…DDIT3 overexpression delays the erythroid differentiation of MDS CD34 + cells by affecting the activation of erythroid transcriptional programs. The inhibition of DDIT3 in CD34 + cells isolated from MDS patients with anemia restores proper erythroid differentiation ( 38 ). Our study showed that the activation of the EIF2AK1 pathway occurs in the later stages of erythroblast maturation, as SF3B1 MT -induced aberrant splicing primarily affected the function of terminally differentiated erythroblasts with the highest mitochondrial content.…”

Normal and dysregulated crosstalk between iron metabolism and erythropoiesis

“…Growing evidence suggests that the heme-regulated EIF2AK1 kinase pathway affects erythropoiesis in health and disease. For example, EIF2AK1 effector DDIT3 is overexpressed in MDS hematopoietic stem and progenitor cells ( Berastegui et al, 2021 ), DDIT3 overexpression delays erythroid differentiation in CD34-positive cells from MDS patients, and EIF2AK1 inhibition increases expression of both mitochondrial heme biosynthesis enzymes and iron transporters, reversing SF3B1 mutation-induced arrest of erythroid differentiation in vitro ( Adema et al, 2022 ).…”