Transcriptomic Analysis Sheds Light on Ineffective Erythropoiesis in MDS with (del)5q

A recent study provides insight into the transcriptomic landscape of normal erythropoiesis and the ineffective erythropoiesis of myelodysplastic syndromes (MDS) with (del)5q and Diamond Blackfan anemia (DBA) at a single-cell resolution.

Raymond Doty, PhD, of the University of Washington; Christopher Lausted, MS, of the Institute for Systems Biology; and colleagues conducted the research and published their findings in Blood Advances.

The anemias of MDS and DBA are “generally macrocytic, always reflect ineffective erythropoiesis, yet result from diverse genetic mutations,” the study’s investigators wrote. “To delineate shared mechanisms that lead to cell death, we studied the fate of single erythroid marrow cells from individuals with DBA and MDS (del)5q.”

They defined healthy and unhealthy differentiation trajectories by using transcriptional pseudotime and cell surface proteins. The researchers found pseudotime trajectories “diverge immediately after cells upregulate transferrin receptor (CD71), import iron, and initiate heme synthesis, although cell death occurs much later.”

In cells that were destined to die, the study’s investigators found high expression of heme-responsive genes, including ribosomal protein and globin genes. However, surviving cells downregulate heme synthesis and upregulate pathways for DNA damage response, hypoxia, and HIF1.

The researchers observed that 24%—plus or minus 12%—of cells from healthy control samples followed the trajectory of unhealthy cells, “implying that heme might serve as a rheostat directing cells to live or die,” they wrote.

When the researchers used succinylacetone to inhibit heme synthesis, more DBA cells took the healthy trajectory and survived. They also noted “high numbers of messages with retained introns that increased as erythroid cells matured, confirmed the rapid cycling of [colony-forming unit-erythroid], and demonstrated that cell cycle timing is an invariant property of differentiation stage.”

Furthermore, including unspliced RNA in pseudotime determinations allowed the researchers to “reliably align independent datasets and accurately query stage-specific” transcriptomic changes, they wrote.

“MDS [with (del)5q] (unlike DBA) results from somatic mutation, so many normal (unmutated) erythroid cells persist,” the study’s authors concluded. “By independently tracking erythroid differentiation of cells with and without chromosome 5q deletions, we gained insight into why 5q[-positive] cells cannot expand to prevent anemia.”

Reference

Doty RT, Lausted CG, Munday AD, et al. The transcriptomic landscape of normal and ineffective erythropoiesis at single-cell resolution. Blood Adv. 2023. doi:10.1182/bloodadvances.2023010382