ZRSR2 endoes a component of the RNA splicing machinery which associates with the U2 auxillary factor and is involved in the recognition of the 3'-splice site during the stages of spliceosome assembly. Mutations in ZRSR2 have been reported in approximately 3-11% of myelodysplasia, 4-8% of chronic myelomonocytic leukemia, 8% of blastic plasmacytoid dendritic cell neoplasm and less than 5% of acute myeloid leukemia and myeloproliferative neoplasms. Unlike other spliceosomal genes, ZRSR2 mutations do not occur in select "hot spots". Nearly all reported mutations are nonsense or frameshift mutations, compatible with loss-of-function mutations and suggesting a tumor suppressor role of ZRSR2. ZRSR2 mutations tend to be exclusive of mutations in most other components of the RNA splicing machinery. Aberrant splicing of U12-type introns has been shown to be a hallmark feature of MDS with ZRSR2 mutations. ZRSR2 mutations are associated with an unfavorable prognosis in myelodysplastic syndrome (NCCN Guidelines for Myelodysplastic Syndromes). ZRSR2 mutations are also reported to be highly specific for secondary acute myeloid leukemia, and may also be helpful in identifying a subset of therapy-related AML and elderly de novo AML with worse clinical outcomes.