Alternative titles; symbols
HGNC Approved Gene Symbol: EED
Cytogenetic location: 11q14.2 Genomic coordinates (GRCh38) : 11:86,244,753-86,287,615 (from NCBI)
| Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
|---|---|---|---|---|
| 11q14.2 | Cohen-Gibson syndrome | 617561 | Autosomal dominant | 3 |
The EED gene encodes an evolutionarily conserved polycomb group (PcG) protein that forms a specific complex, the polycomb repressive complex-2 (PRC2), with 3 other PcG proteins: EZH2 (601573), SUZ12 (606245), and RBBP7/4 (300825/602923). EED and EZH2 are core components of the PRC2, which possesses histone methyltransferase activity and catalyzes trimethylation of histone H3 at lysine 27 (H3K27). The PRC2 complex plays an essential role in regulating chromatin structure and acts as an important regulator of cell development and differentiation during embryogenesis. It also regulates adult tissues through epigenetic gene repression (summary by Imagawa et al., 2017).
In Drosophila, the Polycomb-group (PcG) and trithorax-group (trxG) genes are part of a cellular memory system responsible for the stable inheritance of gene activity. PcG and trxG genes are repressors and activators, respectively, of Drosophila homeotic gene expression. ENX1 (EZH2; 601573) is a mammalian homolog of the Drosophila 'enhancer of zeste' gene and has domains with sequence homology to both PcG and trxG genes. Using a yeast 2-hybrid screen with ENX1 as bait, followed by screening a fetal brain cDNA library, Sewalt et al. (1998) isolated a cDNA encoding EED. EED is the human homolog of Eed, a murine PcG gene homologous to the Drosophila homeotic gene, 'extra sex combs.' The predicted 535-amino acid human EED protein is 100% identical to the murine protein. The N-terminal region of EED contains a putative PEST sequence, which is implicated in protein degradation, and there are 5 WD40 domains throughout the EED protein. WD40 domains are involved in protein-protein interactions, and Sewalt et al. (1998) showed that all 5 are necessary for the ENX1-EED interaction to occur. Northern blot analysis detected 1.5- and 2.0-kb EED transcripts in all tissues and cell lines tested; larger transcripts were detected in normal human tissues only, but at much lower levels. Highest expression was found in testis, spleen, prostate, ovary, and small intestine, as well as in colorectal adenocarcinoma, chronic myeloid leukemia, and osteosarcoma cell lines, with lower levels in thymus, colon, and peripheral blood leukocytes.
Beta-7 integrins (ITGB7; 147559) are involved in the development and/or progression of diseases such as colitis, diabetic insulitis, and lymphoid malignancies, and they play an important role for physiologic functions and pathologic alterations of the immune system. Using a yeast 2-hybrid screen on a Jurkat cell cDNA library with the cytoplasmic tail of ITGB7 as bait, Rietzler et al. (1998) isolated a cDNA encoding EED, which they designated WAIT1. The deduced 441-amino acid protein has a region homologous to a repeat motif in the RCC1 protein (179710) and a region homologous to a repeat motif from the beta subunit of heterotrimeric G proteins (see 139380).
Sewalt et al. (1998) found that ENX1 and EED coimmunoprecipitate, indicating that they also interact in vivo. They do not, however, interact with other PcG proteins, such as PC2 (603079) and BMI1 (164831). Furthermore, ENX1 and EED do not colocalize with HPC2 or BMI1 in nuclear domains of U-2 OS osteosarcoma cells.
Rietzler et al. (1998) demonstrated that EED interacts with the ITGB7 cytoplasmic tail, which regulates receptor avidity and signaling, by coprecipitation from transiently transfected 293 cells. Tyr735 of ITGB7 was critical for the interaction. EED also interacts with the cytoplasmic domains of ITGA4 (192975) and ITGAE (604682), but not with those of ITGB1 (135630), ITGB2 (600065), and ITGAL (153370). The authors concluded that EED may act as a specific regulator of integrin function.
Peytavi et al. (1999) isolated cDNAs encoding EED using the yeast 2-hybrid system on an activated lymphocyte cDNA library with the human immunodeficiency virus-1 (HIV-1) matrix (MA) protein as bait. EED was found to bind MA in vitro and in vivo in yeast cells. The MA and EED proteins colocalized within the nucleus of cotransfected human cells. This and the failure of EED to bind to uncleaved GAG precursor suggested a role for EED at the early stages of virus infection, rather than late in the virus life cycle.
In marsupials and the extraembryonic region of the mouse, X inactivation is imprinted: the paternal X chromosome is preferentially inactivated whereas the maternal X is always active. Having more than 1 active X chromosome is deleterious to extraembryonic development in the mouse. Wang et al. (2001) showed that the eed gene is required for primary and secondary trophoblast giant cell development in female embryos. Results from mice carrying a paternally inherited X-linked GFP transgene implicated eed in the stable maintenance of imprinted X inactivation in extraembryonic tissues. Based on the recent finding that the EED protein interacts with histone deacetylases, Wang et al. (2001) suggested that this maintenance activity involves hypoacetylation of the inactivated paternal X chromosome in the extraembryonic tissues.
Cao et al. (2002) reported the purification and characterization of an EED-EZH2 complex, the human counterpart of the Drosophila ESC-E(Z) complex. Cao et al. (2002) demonstrated that the complex specifically methylates nucleosomal histone H3 (see 602812) at lysine-27 (H3-K27). Using chromatin immunoprecipitation assays, Cao et al. (2002) showed that H3-K27 methylation colocalizes with, and is dependent on, E(Z) binding at an 'Ultrabithorax' (Ubx) Polycomb response element, and that this methylation correlates with Ubx expression. Methylation on H3-K27 facilitates binding of Polycomb, a component of the Polycomb repressive complex 1 (PRC1 complex), to the histone H3 N-terminal tail. Thus, Cao et al. (2002) concluded that their studies established a link between histone methylation and Polycomb group-mediated gene silencing. The complex responsible for histone methyltransferase activity includes EZH2 (601573), SUZ12 (606245), and EED. EZH2 contains a SET domain, a signature motif for all known histone lysine methyltransferases except the H3-K79 methyltransferase DOT1, and is therefore likely to be the catalytic subunit.
Plath et al. (2003) demonstrated that transient recruitment of the EED-EZH2 complex to the inactive X chromosome occurs during initiation of X inactivation in both extraembryonic and embryonic cells and is accompanied by H3-K27 methylation. Recruitment of the complex and methylation on the inactive X depend on Xist (314670) RNA but are independent of its silencing function. Plath et al. (2003) concluded that taken together, their results suggest a role for EED-EZH2-mediated H3-K27 methylation during initiation of both imprinted and random X inactivation and demonstrate that H3-K27 methylation is not sufficient for silencing of the inactive X.
To gain insight into the role of Polycomb group (PcG) proteins in embryonic stem (ES) cells, Boyer et al. (2006) identified the genes occupied by PcG proteins in murine ES cells by performing genomewide location analysis using antibodies against core components of PRC1 (Phc1, 602978 and Rnf2, 608985) and PRC2 (Suz12 and Eed). Boyer et al. (2006) found that the Polycomb repressive complexes PRC1 and PRC2 co-occupied 512 genes, many of which encode transcription factors with important roles in development. All of the co-occupied genes contained modified nucleosomes (trimethylated lys27 on histone H3; see 602810). Consistent with a causal role in gene silencing in ES cells, PcG target genes were derepressed in cells deficient for the PRC2 component Eed, and were preferentially activated on induction of differentiation. Boyer et al. (2006) concluded that dynamic repression of developmental pathways by Polycomb complexes may be required for maintaining ES cell pluripotency and plasticity during embryonic development.
By mass spectrometric analysis, Higa et al. (2006) identified over 20 WD40 repeat-containing (WDR) proteins that interacted with the CUL4 (see 603137)-DDB1 (600045)-ROC1 (RBX1; 603814) complex, including EED. Sequence alignment revealed that most of the interacting WDR proteins had a centrally positioned WDxR/K submotif. Knockdown studies suggested that the WDR proteins functioned as substrate-specific adaptors. For example, inactivation of L2DTL (DTL; 610617), but not other WDR proteins, prevented CUL4-DDB1-dependent proteolysis of CDT1 (605525) following gamma irradiation. Inactivation of WDR5 (609012) or EED, but not other WDR proteins, altered the pattern of CUL4-DDB1-dependent histone H3 methylation.
The gene silencing activity of the Polycomb repressive complex-2 (PRC2; see 601674) depends on its ability to trimethylate lys27 of histone 3 (H3K27) by the catalytic SET domain of the EZH2 (601573) subunit and at least 2 other subunits of the complex: SUZ12 (606245) and EED. Margueron et al. (2009) showed that the carboxy-terminal domain of EED specifically binds to histone tails carrying trimethyl-lysine residues associated with repressive chromatin marks, and that this leads to the allosteric activation of the methyltransferase activity of PRC2. Mutations in EED that prevent it from recognizing repressive trimethyl-lysine marks abolished the activation of PRC2 in vitro and, in Drosophila, reduced global methylation and disrupted development. Margueron et al. (2009) concluded that their findings suggested a model for the propagation of the H3K27 methyl-3 mark that accounts for the maintenance of repressive chromatin domains and for the transmission of a histone modification from mother to daughter cells.
By FISH, Schumacher et al. (1998) mapped the EED gene to 11q14.2-q22.3.
In a 27-year-old man, born of unrelated Turkish parents, with Cohen-Gibson syndrome (COGIS; 617561), Cohen et al. (2015) identified a de novo heterozygous missense mutation in the EED gene (R302S; 605984.0001). The mutation was found by whole-exome sequencing and confirmed by Sanger sequencing. Functional studies of the variant and studies of patient cells were not performed.
In a 22-year-old man, born of unrelated Caucasian parents, with COGIS, Cohen and Gibson (2016) identified a de novo heterozygous missense mutation in the EED gene (H258Y; 605984.0002). The mutation was found by Sanger sequencing. Functional studies of the variant and studies of patient cells were not performed.
In a 16-year-old girl, born of unrelated Hispanic parents, with COGIS, Cooney et al. (2017) identified a heterozygous missense mutation in the EED gene (R302G; 605984.0003). The mutation, which was found by whole-exome sequencing, was not present in the mother; the father was unavailable for testing. Functional studies of the variant and studies of patient cells were not performed.
In a 5-year-old Japanese boy with COGIS, Imagawa et al. (2017) identified a de novo heterozygous missense mutation in the EED gene (R236T; 605984.0004). The mutation was found by whole-exome sequencing and confirmed by Sanger sequencing. In vitro functional expression studies showed that the R236T and R302S mutant proteins were associated with decreased levels of H3K27me3 compared to wildtype, and Western blot analysis of patient cells with the R236T mutation also showed loss of H3K27me3, consistent with loss of PRC2 activity and a loss of function.
Ikeda et al. (2016) found that mice with a conditional deletion of Eed exhibited early death accompanied by a rapid decrease in hemopoietic cells, particularly stem/progenitor cells (HSPCs), with impaired bone marrow repopulation ability. Cell cycle analysis of HSPCs demonstrated increased S-phase fraction and suppressed G0/G1 entry. Eed-deleted HSPCs showed enrichment of genes encoding cell adhesion molecules and increased attachment to fibronectin (FN1; 135600). Ikeda et al. (2016) proposed that Eed deficiency increases proliferation and promotes quiescence, possibly by enhanced adhesion to the hemopoietic niche, leading to abnormal differentiation and functional defects. Eed haploinsufficiency induced hemopoietic dysplasia. Mice heterozygous for Eed deletion were susceptible to malignant transformation and developed leukemia accompanied by Evi1 (MECOM; 165215) overexpression. Ikeda et al. (2016) concluded that EED has differentiation stage-specific and dose-dependent roles in normal hemopoiesis and leukemogenesis.
EED interacts with trimethylated histone H3K27 through its aromatic cage structure composed of phe97, trp364, and tyr365. This interaction activates the histone methyltransferase activity of PRC2 and propagates repressive histone marks. Ueda et al. (2016) generated mice expressing a myeloid disorder-associated Eed mutation, ile363 to met (I363M), analogous to mutations in the aromatic cage. Mice homozygous for I363M showed preferential reduction of trimethylated H3K27 and died at midgestation. Heterozygotes showed increased clonogenic capacity and bone marrow-repopulating activity in HSPCs and were susceptible to leukemia. The PRC2 target gene, Lgals3 (153619), which encodes a multifunctional galactose-binding lectin, was derepressed in heterozygotes and enhanced the stem cell features of HSPCs. Ueda et al. (2016) concluded that the structural integrity of EED to H3K27 trimethylation propagation is critical for embryonic development and hemopoietic homeostasis, and that perturbation of this structure leads to increased predisposition to hematologic malignancies.
In a 27-year-old man, born of unrelated Turkish parents, with Cohen-Gibson syndrome (COGIS; 617561), Cohen et al. (2015) identified a de novo heterozygous c.906A-C transversion (c.906A-C, NM_003797.3) in the EED gene, resulting in an arg302-to-ser (R302S) substitution at a conserved residue in a WD40 domain that is required for H3K27 methylation and is possibly necessary for the EED-EZH2 interaction. The mutation, which was found by whole-exome sequencing and confirmed by Sanger sequencing, was not found in the dbSNP or Exome Variant Server databases, or in an in-house database of 587 Turkish exomes. Functional studies of the variant and studies of patient cells were not performed. (In the article by Cohen et al. (2015), the nucleotide change was reported as a c.1372A-C transversion; Gibson (2017) confirmed that the correct change is c.906A-C.)
Through in vitro functional expression studies, Imagawa et al. (2017) demonstrated that the R302S mutant protein was associated with decreased levels of H3K27me3 compared to wildtype, consistent with loss of PRC2 activity and a loss of function.
In a 22-year-old man, born of unrelated Caucasian parents, with Cohen-Gibson syndrome (COGIS; 617561), Cohen and Gibson (2016) identified a de novo heterozygous c.772C-T transition (c.772C-T, NM_003797.4) in the EED gene, resulting in a his258-to-tyr (H258Y) substitution at a conserved residue in the fourth WD40 domain that is required for H3K27 methylation and is possibly necessary for the EED-EZH2 interaction. The mutation, which was found by Sanger sequencing, was not found in the dbSNP or Exome Variant Server databases. Functional studies of the variant and studies of patient cells were not performed.
In a 16-year-old girl, born of unrelated Hispanic parents, with Cohen-Gibson syndrome (COGIS; 617561), Cooney et al. (2017) identified a heterozygous c.904A-G transition in the EED gene, resulting in an arg302-to-gly (R302G) substitution. The mutation, which was found by whole-exome sequencing, was not present in the mother; the father was unavailable for testing. The mutation was not found in the 1000 Genomes Project or ExAC databases. Functional studies of the variant and studies of patient cells were not performed. The mutation occurred at the same residue as another putatively pathogenic EED mutation (R302S; 605984.0001).
In a 5-year-old Japanese boy with Cohen-Gibson syndrome (COGIS; 617561), Imagawa et al. (2017) identified a de novo heterozygous c.707G-C transversion in the EED gene, resulting in an arg236-to-thr (R236T) substitution at a highly conserved residue between the WD40 repeats. The mutation, which was found by whole-exome sequencing and confirmed by Sanger sequencing, was not found in the dbSNP (build 137), 1000 Genomes Project, Exome Sequencing Project, or ExAC databases, or in an in-house database of 575 Japanese exomes. In vitro functional expression studies showed that the mutant protein was associated with decreased levels of H3K27me3 compared to wildtype, consistent with a loss of function. Western blot analysis of patient cells also showed loss of H3K27me3.
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