Downregulation of UBA1 Expression in Myelodysplastic Syndrome

Somatic loss-of-function mutations of the ubiquitin-activating enzyme E1 gene (UBA1) that occur in VEXAS syndrome (vacuoles, E1 enzyme, X-linked, auto-inflammatory, somatic) also occur in myelodysplastic syndrome (MDS). This suggests that impairment of UBA1 activity contributes to the pathogenesis of these diseases, which are both characterized by systemic inflammation. We sought to determine whether abnormal expression of UBA1 in MDS contributes to disease development. We analyzed RNA sequencing results obtained from CD34+ bone marrow hematopoietic stem and progenitor cells of patients with treatment-naive MDS or chronic myelomonocytic leukemia and from heathy donors, and we detected significant downregulation of UBA1 RNA expression in MDS. In patients with MDS without excess blasts, UBA1 downregulation was associated with altered innate immune and autophagy signaling and co-occurred with SF3B1 mutations. Moreover, in cultured human bone marrow hematopoietic stem and progenitor cells and in mice, pharmacologic inhibition of UBA1 led to impaired hematopoietic repopulating activity, particularly in the erythroid compartment. These results indicate that, in addition to somatic mutations, downregulation of UBA1 may play a role in MDS pathogenesis.