Interconnections between DDX41-Dependent Post-Transcriptional and GATA Factor-Instigated Transcriptional Mechanisms That Govern Hematopoiesis

• Published in: Blood 2023-11, Vol.142 (Supplement 1), p.1073-1073
• Main Authors: Jurotich, Christina, Kim, Jeong-Ah, Johnson, Kirby D., Shen, Siqi, Liao, Ruiqi, Churpek, Jane E, Keles, Sunduz, Bresnick, Emery H.
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2023-182319

Heterozygous DDX41 germline mutations occur in familial myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML) and acute erythroid leukemia (AEL). DDX41 encodes an RNA helicase that regulates RNA splicing, cGAS-Sting signaling in innate immunity, and maintains genome stability in erythropoiesis. We described the innovation of a facile genetic rescue system to compare RNA-regulatory activities of wild type and disease-associated DDX41 variants in engineered HoxB8-immortalized (hi) murine myeloid progenitor cells (hi-Ddx41+/+ and Ddx41+/- cells) (Kim et al., Leukemia 2023). We identified DDX41-regulated transcripts and membrane proteins as quantitative metrics of DDX41 activity that discriminate benign from pathogenic DDX41 alleles. As these transcripts and the cognate proteins were not known to be components of GATA2 genetic networks that govern hematopoietic stem/progenitor cell (HSPC) transitions, we hypothesized that DDX41 mechanisms in progenitors operate in parallel with or independent of GATA2 mechanisms. Considering the biological and pathological importance of DDX41 and many unanswered questions on how clinical variants impact DDX41 activity, we instituted studies to discover DDX41-regulated transcript isoforms. The datasets are being used to unveil how DDX41 controls cellular functions, how clinical variants derail mechanisms, and to establish interconnections or independence with GATA factor mechanisms. To develop a broader perspective, we extended the myeloid data by innovating a rescue system to analyze DDX41 structure/function in G1E-ER-GATA1 erythroblasts that express a conditionally active ER-GATA1 allele. We used CRISPR/Cas9 to generate Ddx41+/- clonal lines that expressed ~50% lower levels of DDX41 protein. A comparable system is being generated in human HUDEP2 erythroid precursor cells. We compared DDX41 with two disease-associated germline variants: G173R and K331deletion. G1E-ER-GATA1- Ddx41 +/-cells were infected with retrovirus expressing GFP, or GFP and DDX41 (WT, G173R, or K331del), GFP + cells were sorted, and total RNA was analyzed by RNA-seq. Differential expression analysis revealed 138 Ddx41-regulated transcripts (P < 0.05), with 63 elevated and 75 decreased. Disease-associated variants failed to regulate these transcripts. To establish relationships between DDX41-regulated and GATA1-regulated transcripts in erythroblasts, we compared DDX41-regulated transcripts with our GATA1 transcriptomic data (Tanimura et al., EMBO Rep.