Dead-box helicase 41 (DDX41) is a known sensor of nucleic acids that contributes to the interferon response to retroviruses. DDX41 belongs to a family of RNA helicases, with distinct DEAD/H box (Asp-Glu-Ala-Asp/His) domains, whose members have been implicated in translation, ribosome biogenesis, nuclear-cytoplasmic transport, organelle gene expression and pre-mRNA splicing. DDX41 was also recently identified as a tumor suppressor gene in familial and sporadic myelodysplastic syndrome/acute myeloid leukemia (MDS/AML), as well as other hematological malignancies. In MDS/AML, DDX41 is thought to interact with spliceosomal components and alter splicing, resulting in the inactivation of tumor suppressor genes or alterations in the balance of gene isoforms, although whether this occurs through protein-RNA, protein-DNA or protein-protein interactions is not known. We recently developed mice with a floxed allele of DDX41, which will allow us for the first time to study DDX41's role in hematopoietic development and transformation. DDX41 germline knockouts die prior to E10 in development, but mice heterozygous for the knockout are completely viable and will be used to determine whether these mice develop myelodysplasias. We have also generated conditional knockouts that delete the gene in hematopoietic stem cells (HSC). The HSCs will be used to study the role of DDX41 in hematopoietic lineage differentiation. RNA Seq analysis on the knockout HSCs will be performed, to determine if loss of DDX41 results in altered gene expression or splicing defects. The HSCs will be transduced with wild type and mutant DDX41; in particular, we will engineer patient-derived mutations as well those in the DEAD and helicase domains, to begin to determine how this protein functions in development and transformation. We propose to use these mice to study the role of DDX41 in HSC development, as well as to determine the mechanism by which it regulates transformation of myeloid cells. These studies are likely to further our understanding of AML as well as to generate a model system for testing potential therapeutics.
MDS/AML is a late onset disease of familial and sporadic origin with 5-year survival rates of ~25%. One of the most commonly mutated genes found in both autosomal dominant familial and sporadic disease is DEAD-box helicase 41 (DDX41). We have generated a DDX41 mouse knockout model, which will allow us to understand the role of this factor in HSC development and myelodysplastic disorders.