DDX41-associated susceptibility to myeloid neoplasms

Deleterious germ line DDX41 variants confer risk for myeloid neoplasms (MNs) and less frequently for lymphoid malignancies, with autosomal dominant inheritance and an estimated prevalence of 3% among MNs. Germ line DDX41 variants include truncating alleles that comprise about two-thirds of all alleles, missense variants located preferentially within the DEAD-box domain, and deletion variants. The identification of a truncating allele on tumor-based molecular profiling should prompt germ line genetic testing because >95% of such alleles are germ line. Somatic mutation of the wild-type DDX41 allele occurs in about half of MNs with germ line DDX41 alleles, typically in exons encoding the helicase domain and most frequently as R525H. Several aspects of deleterious germ line DDX41 alleles are noteworthy: (1) certain variants are common in particular populations, (2) MNs develop at older ages typical of de novo disease, challenging the paradigm that inherited cancer risk always causes disease in young people, (3) despite equal frequencies of these variants in men and women, men progress to MNs more frequently, suggesting a gender-specific effect on myeloid leukemogenesis, and (4) individuals with deleterious germ line DDX41 variants develop acute severe graft-versus-host disease after allogeneic hematopoietic cell transplantation with wild-type donors more than others unless they receive posttransplant cyclophosphamide, suggesting a proinflammatory milieu that stimulates donor-derived T cells. Biochemical studies and animal models have identified DDX41's ability to interact with double-stranded DNA and RNA:DNA hybrids with roles in messenger RNA splicing, ribosomal RNAs or small nucleolar RNAs processing, and modulation of innate immunity, disruption of which could promote inflammation and drive tumorigenesis.