EZH2 encodes the histone methyltransferase subunit of the polycomb repressive complex 2 (PRC2) that leads to H3K27me3 and promotes transcriptional repression. EZH2 loss of function mutations (nonsense, frameshift mutations, occasionally occurring as homozygous mutations) may occur throughout the gene and have been reported in less than 10% of patients with acute myeloid leukemia, myelodysplasia, atypical chronic myelogenous leukemia, primary myelofibrosis and up to 12% of patients with chronic myelomonocytic leukemia. EZH2 loss of function mutations may be more frequent (15%) among cases of T cell acute lymphoblastic leukemia. EZH2 mutations have been independently associated with adverse prognosis in MDS and MDS/MPN. Therapeutic targeting of EZH2 is currently under study for some types of lymphoma and solid tumors.

EZH2 encodes the histone methyltransferase subunit of the polycomb repressive complex 2 (PRC2) that leads to H3K27me3 and promotes transcriptional repression. EZH2 loss of function mutations (nonsense, frameshift mutations, occasionally occurring as homozygous mutations) may occur throughout the gene and have been reported in less than 10% of patients with acute myeloid leukemia, myelodysplasia, atypical chronic myelogenous leukemia, primary myelofibrosis and up to 12% of patients with chronic myelomonocytic leukemia. EZH2 loss of function mutations may be more frequent (15%) among cases of T cell acute lymphoblastic leukemia. EZH2 mutations have been independently associated with adverse prognosis in MDS and MDS/MPN. Therapeutic targeting of EZH2 is currently under study for some types of lymphoma and solid tumors.

This gene is a known cancer gene.

This gene is a known cancer gene.

EED is a component of the polycomb repressor complex 2 (PRC2). Missense and frameshift mutations have been described in T cell acute lymphoblastic leukemia and may be enriched in the early T cell precursor subtype of that disease(found in appromimately 5% of such cases). In addition, mutations of EED have been described in, overall, less than 5% of myeloid neoplasms including cases of CMML, AML and MDS. EED mutations tend to be exclusive of mutations in EZH2, another component of PRC2. Deletions of EED have also been described which are not detected by this assay.

SUZ12 is one of the core components of the polycomb repressive complex 2 (PRC2), which is a highly conserved histone H3 lysine 27 methyltransferase that regulates the expression of developmental genes. SUZ12 mutations are present infrequently (<2%) in myeloproliferative neoplasms (MPN) and myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN). The mutations are missense and tend to be located at the highly conserved VEFS domain, is required for the interaction between SUZ12 and EZH2. These mutations reduced PRC2 histone methyltransferase activity in vitro. Inactivating mutations of the catalytic component of PRC2, EZH2, can also be seen in myeloid neoplasms. Mice with loss of function mutations in PRC2 components display enhanced activity of their hematopoietic stem cell/progenitor population and loss of SUZ12 function in particular enhances hematopoietic stem cell activity.

The GATA1 transcription factor is important in the development of erythroid and megakaryocytic lineages. Amino-terminal, small insertion/deletion(frameshift), nonsense and missense mutations of GATA1 have been described in almost all patients with transient abnormal myelopoiesis(TAM) and acute megakaryoblastic leukemia associated with Down syndrome (Trisomy 21)(DS-AMKL). Studies suggest that the cases of TAM which progress to DS-AMKL are associated with the acquisition of additional driver mutations in other genes including the cohesin complex genes as well as CTCF and EZH2. The amino-terminal GATA1 mutations lead to a lack of the N-terminal amino acids and translation from an alternate start codon (methionine at position 84 in exon 3). GATA1 mutations appear to be rare in acute megakaryoblastic leukemia not associated with Down syndrome. GATA1 mutations have also been reported in the context of hereditary myeloid disorders. If clinical findings and family history are concerning for an inherited disorder, then genetic counseling may be helpful, if clinically indicated.

CBL (casitas-B-lineage lymphoma) gene mutations have been identified in approximately 15% of chronic myelomonocytic leukemia, 15% of juvenile myelomonocytic leukemia, 15% of secondary AML(from MDS or MDS/MPN overlap syndrome) and rare or absent in polycythemia vera, essential thrombocythemia, primary myelofibrosis, chronic eosinophilic leukemia and MDS. Also, CBL mutations are found in only 1% of de novo acute leukemias and tend to be associated with core binding factor acute myeloid leukemia (AML) among AML cases. CBL is a Ras pathway gene and has been associated with hereditary myeloid disorders. CBL ubiquitinylates and degrades activated receptor and non-receptor tyrosine kinases via the E3-ligase activity of its RING domain. CBL also acts as an adaptor for downstream cell signal transduction, via its tyrosine kinase binding domain. Most variants of the CBL protein are missense substitutions in the zinc binding RING domain (amino acids 366-420) (exons 8-9) that abrogate CBL ubiquitin ligase activity but retain other functions. Pathogenic mutations are believed to be oncogenic by a variety of potential mechanisms including increased Ras pathway activation, aberrant phosphoSTAT5 and/or increased KIT expression in different cellular contexts. Occasionally, two CBL mutations may be present or CBL mutations may be associated with uniparental disomy. In addition, CBL mutations may occur together with mutations in other genes ( RUNX1, ASXL1, TET2 or EZH2 ). According to some studies, mutations of CBL may be associated with reduced overall survival in MDS.

SRSF2 is a member of the serine/arginine-rich family of pre-mRNA splicing factors, which constitute part of the spliceosome. It interacts with other spliceosomal components bound to both the 5- and 3-splice sites during spliceosome assembly. SRSF2 mutations typically occur as missense mutations at Pro95. SRSF2 mutations have been reported in approximately 40% of cases of chronic myelomonocytic leukemia, but they may not have prognostic significance in that entity. Comutation of TET2 and SRSF2 was highly predictive of a myeloid neoplasm characterized by myelodysplasia and monocytosis, including but not limited to, chronic myelomonocytic leukemia. In addition, SRSF2 mutations have been reported in approximately 15-20% of cases of myelodysplastic syndrome. SRSF2 mutations have also been described in 5-20% of patients with acute myeloid leukemia and appear to be enriched among AML patients with reduced blast counts. SRSF2 has been found to be mutated in approximately 10% of cases of primary myelofibrosis where mutations may occur together with mutations in JAK2, MPL, TET2, CBL, ASXL1, EZH2, IDH1/2. SRSF2 mutations are also present in 8% of blastic plasmacytoid dendritic cell neoplasm and 3% of polythemia vera. SRSF2 mutations tend to be (although are not entirely) exclusive of mutations in other splicing factor components. SRSF2 mutations are associated with a poor prognosis in myelodysplastic syndrome (NCCN Guidelines for Myelodysplastic Syndromes), primary myelofibrosis, polycythemia vera, and KIT D816V-mutated advanced systemic mastocytosis. SRSF2 mutations are also reported to be highly specific for secondary acute myeloid leukemia, and may also be helpful in identifying a subset of elderly patients with de novo acute myeloid leukemia and therapy-related AML with worse clinical outcomes.