Malignant phyllodes tumor with EGFR variant III mutation: A rare case report with immunohistochemical and genomic studies.

A female in her 60's presented with a left-sided breast mass. A core needle biopsy specimen showed diffuse proliferation of a round cell tumor, which was positive for vimentin, NKX2.2, BCOR, and focal CD99 on immunohistochemistry (IHC). No fusion genes of the Ewing family sarcomas were detected. With a tentative diagnosis of primary breast sarcoma (PBS), total mastectomy was performed after chemotherapy. The resected tissues showed proliferation of round or spindle-shaped tumor cells with a high nuclear-to-cytoplasmic ratio, exhibiting solid and fascicular arrangements but no epithelial component or organoid pattern. While IHC indicated no particular histological diagnosis, genomic examination revealed gene alterations in MED12 p.G44D, MLL2 (KMT2D) p.T1496fs*27, and EGFR variant III (vIII). Moreover, a retrospective IHC study showed overexpression of EGFRvIII. A malignant phyllodes tumor (PT) with extensive sarcomatous overgrowth was indicated as an integrative diagnosis. This is a rare case of a malignant PT harboring EGFRvIII. The present case provides an importance of accurate diagnosis and genomic analysis of rare breast tumors, as malignant PT and PBS are different in its treatment strategy and prognosis.

Human Genetics of Ventricular Septal Defect.

Ventricular septal defects (VSDs) are recognized as one of the commonest congenital heart diseases (CHD), accounting for up to 40% of all cardiac malformations, and occur as isolated CHDs as well as together with other cardiac and extracardiac congenital malformations in individual patients and families. The genetic etiology of VSD is complex and extraordinarily heterogeneous. Chromosomal abnormalities such as aneuploidy and structural variations as well as rare point mutations in various genes have been reported to be associated with this cardiac defect. This includes both well-defined syndromes with known genetic cause (e.g., DiGeorge syndrome and Holt-Oram syndrome) and so far undefined syndromic forms characterized by unspecific symptoms. Mutations in genes encoding cardiac transcription factors (e.g., NKX2-5 and GATA4) and signaling molecules (e.g., CFC1) have been most frequently found in VSD cases. Moreover, new high-resolution methods such as comparative genomic hybridization enabled the discovery of a high number of different copy number variations, leading to gain or loss of chromosomal regions often containing multiple genes, in patients with VSD. In this chapter, we will describe the broad genetic heterogeneity observed in VSD patients considering recent advances in this field.

Epigenetics.

Epigenetics is the study of heritable changes to the genome and gene expression patterns that are not caused by direct changes to the DNA sequence. Examples of these changes include posttranslational modifications to DNA-bound histone proteins, DNA methylation, and remodeling of nuclear architecture. Collectively, epigenetic changes provide a layer of regulation that affects transcriptional activity of genes while leaving DNA sequences unaltered. Sequence variants or mutations affecting enzymes responsible for modifying or sensing epigenetic marks have been identified in patients with congenital heart disease (CHD), and small-molecule inhibitors of epigenetic complexes have shown promise as therapies for adult heart diseases. Additionally, transgenic mice harboring mutations or deletions of genes encoding epigenetic enzymes recapitulate aspects of human cardiac disease. Taken together, these findings suggest that the evolving field of epigenetics will inform our understanding of congenital and adult cardiac disease and offer new therapeutic opportunities.

Human Genetics of Semilunar Valve and Aortic Arch Anomalies.

Lesions of the semilunar valve and the aortic arch can occur either in isolation or as part of well-described clinical syndromes. The polygenic cause of calcific aortic valve disease will be discussed including the key role of NOTCH1 mutations. In addition, the complex trait of bicuspid aortic valve disease will be outlined, both in sporadic/familial cases and in the context of associated syndromes, such as Alagille, Williams, and Kabuki syndromes. Aortic arch abnormalities particularly coarctation of the aorta and interrupted aortic arch, including their association with syndromes such as Turner and 22q11 deletion, respectively, are also discussed. Finally, the genetic basis of congenital pulmonary valve stenosis is summarized, with particular note to Ras-/mitogen-activated protein kinase (Ras/MAPK) pathway syndromes and other less common associations, such as Holt-Oram syndrome.

PI 3-Kinase and the Histone Methyl-Transferase KMT2D Collaborate to Induce Arp2/3-Dependent Migration of Mammary Epithelial Cells.

Breast cancer develops upon sequential acquisition of driver mutations in mammary epithelial cells; however, how these mutations collaborate to transform normal cells remains unclear in most cases. We aimed to reconstitute this process in a particular case. To this end, we combined the activated form of the PI 3-kinase harboring the H1047R mutation with the inactivation of the histone lysine methyl-transferase KMT2D in the non-tumorigenic human mammary epithelial cell line MCF10A. We found that PI 3-kinase activation promoted cell-cycle progression, especially when growth signals were limiting, as well as cell migration, both in a collective monolayer and as single cells. Furthermore, we showed that KMT2D inactivation had relatively little influence on these processes, except for single-cell migration, which KMT2D inactivation promoted in synergy with PI 3-kinase activation. The combination of these two genetic alterations induced expression of the ARPC5L gene that encodes a subunit of the Arp2/3 complex. ARPC5L depletion fully abolished the enhanced migration persistence exhibited by double-mutant cells. Our reconstitution approach in MCF10A has thus revealed both the cell function and the single-cell migration, and the underlying Arp2/3-dependent mechanism, which are synergistically regulated when KMT2D inactivation is combined with the activation of the PI 3-kinase.

H3K4me1 facilitates promoter-enhancer interactions and gene activation during embryonic stem cell differentiation.

Histone H3 lysine 4 mono-methylation (H3K4me1) marks poised or active enhancers. KMT2C (MLL3) and KMT2D (MLL4) catalyze H3K4me1, but their histone methyltransferase activities are largely dispensable for transcription during early embryogenesis in mammals. To better understand the role of H3K4me1 in enhancer function, we analyze dynamic enhancer-promoter (E-P) interactions and gene expression during neural differentiation of the mouse embryonic stem cells. We found that KMT2C/D catalytic activities were only required for H3K4me1 and E-P contacts at a subset of candidate enhancers, induced upon neural differentiation. By contrast, a majority of enhancers retained H3K4me1 in KMT2C/D catalytic mutant cells. Surprisingly, H3K4me1 signals at these KMT2C/D-independent sites were reduced after acute depletion of KMT2B, resulting in aggravated transcriptional defects. Our observations therefore implicate KMT2B in the catalysis of H3K4me1 at enhancers and provide additional support for an active role of H3K4me1 in enhancer-promoter interactions and transcription in mammalian cells.

lncCPSET1 acts as a scaffold for MLL2/COMPASS to regulate Bmp4 and promote the formation of chicken primordial germ cells.

Primordial germ cells (PGCs) are the ancestors of female and male germ cells. Recent studies have shown that long non-coding RNA (lncRNA) and histone methylation are key epigenetic factors affecting PGC formation; however, their joint regulatory mechanisms have rarely been studied. Here, we explored the mechanism by which lncCPSET1 and H3K4me2 synergistically regulate the formation of chicken PGCs for the first time. Combined with chromatin immunoprecipitation (CHIP) sequencing and RNA-seq of PGCs transfected with the lncCPSET1 overexpression vector, GO annotation and KEGG enrichment analysis revealed that Wnt and TGF-ß signaling pathways were significantly enriched, and Fzd2, Id1, Id4, and Bmp4 were identified as candidate genes. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) showed that ASH2L, DPY30, WDR5, and RBBP5 overexpression significantly increased the expression of Bmp4, which was up-regulated after lncCPSET1 overexpression as well. It indicated that Bmp4 is a target gene co-regulated by lncCPSET1 and MLL2/COMPASS. Interestingly, co-immunoprecipitation results showed that ASH2L, DPY30 and WDR5 combined and RBBP5 weakly combined with DPY30 and WDR5. lncCPSET1 overexpression significantly increased Dpy30 expression and co-immunoprecipitation showed that interference/overexpression of lncCPSET1 did not affect the binding between the proteins in the complexes, but interference with lncCPSET1 inhibited DPY30 expression, which was confirmed by RNA immunoprecipitation that lncCPSET1 binds to DPY30. Additionally, CHIP-qPCR results showed that DPY30 enriched in the Bmp4 promoter region promoted its transcription, thus promoting the formation of PGCs. This study demonstrated that lncCPSET1 and H3K4me2 synergistically promote PGC formation, providing a reference for the study of the regulatory mechanisms between lncRNA and histone methylation, as well as a molecular basis for elucidating the formation mechanism of PGCs in chickens.

Attention challenges in Kabuki syndrome.

BACKGROUND: Understanding the specific neurobehavioural profile of rare genetic diseases enables clinicians to provide the best possible care for patients and families, including prognostic and treatment advisement. Previous studies suggested that a subset of individuals with Kabuki syndrome (KS), a genetic disorder causing intellectual disability and other neurodevelopmental phenotypes, have attentional deficits. However, these studies looked at relatively small numbers of molecularly confirmed cases and often used retrospective clinical data instead of standardised assessments. METHODS: Fifty-five individuals or caregivers of individuals with molecularly confirmed KS completed assessments to investigate behaviour and adaptive function. Additionally, information was collected on 23 unaffected biological siblings as controls. RESULTS: Attention Problems in children was the only behavioural category that, when averaged, was clinically significant, with the individual scores of nearly 50% of the children with KS falling in the problematic range. Children with KS scored significantly higher than their unaffected sibling on nearly all behavioural categories. A significant correlation was found between Attention Problems scores and adaptive function scores (P = 0.032), which was not explained by lower general cognitive ability. CONCLUSIONS: We found that the rates of children with attentional deficits are much more elevated than would be expected in the general population, and that attention challenges are negatively correlated with adaptive function. When averaged across KS participants, none of the behavioural categories were in the clinically significant range except Attention Problems for children, which underscores the importance of clinicians screening for attention deficit hyperactivity disorder (ADHD) in children with KS.

KMT2D links TGF-ß signaling to noncanonical activin pathway and regulates pancreatic cancer cell plasticity.

Although KMT2D, also known as MLL2, is known to play an essential role in development, differentiation, and tumor suppression, its role in pancreatic cancer development is not well understood. Here, we discovered a novel signaling axis mediated by KMT2D, which links TGF-ß to the activin A pathway. We found that TGF-ß upregulates a microRNA, miR-147b, which in turn leads to post-transcriptional silencing of KMT2D. Loss of KMT2D induces the expression and secretion of activin A, which activates a noncanonical p38 MAPK-mediated pathway to modulate cancer cell plasticity, promote a mesenchymal phenotype, and enhance tumor invasion and metastasis in mice. We observed a decreased KMT2D expression in human primary and metastatic pancreatic cancer. Furthermore, inhibition or knockdown of activin A reversed the protumoral role of KMT2D loss. These findings support a tumor-suppressive role of KMT2D in pancreatic cancer and identify miR-147b and activin A as novel therapeutic targets.

KMT2D Deficiency Causes Sensorineural Hearing Loss in Mice and Humans.

Individuals with Kabuki syndrome type 1 (KS1) often have hearing loss recognized in middle childhood. Current clinical dogma suggests that this phenotype is caused by frequent infections due to the immune deficiency in KS1 and/or secondary to structural abnormalities of the ear. To clarify some aspects of hearing loss, we collected information on hearing status from 21 individuals with KS1 and found that individuals have both sensorineural and conductive hearing loss, with the average age of presentation being 7 years. Our data suggest that while ear infections and structural abnormalities contribute to the observed hearing loss, these factors do not explain all loss. Using a KS1 mouse model, we found hearing abnormalities from hearing onset, as indicated by auditory brainstem response measurements. In contrast to mouse and human data for CHARGE syndrome, a disorder possessing overlapping clinical features with KS and a well-known cause of hearing loss and structural inner ear abnormalities, there are no apparent structural abnormalities of the cochlea in KS1 mice. The KS1 mice also display diminished distortion product otoacoustic emission levels, which suggests outer hair cell dysfunction. Combining these findings, our data suggests that KMT2D dysfunction causes sensorineural hearing loss compounded with external factors, such as infection.

Corrigendum: LncRNA FOXP4-AS1 promotes the progression of esophageal squamous cell carcinoma by interacting with MLL2/H3K4me3 to upregulate FOXP4.

[This corrects the article DOI: 10.3389/fonc.2021.773864.].

Neurobehavioral phenotype of Kabuki syndrome: Anxiety is a common feature.

Kabuki syndrome (KS) is a Mendelian Disorder of the Epigenetic Machinery (MDEM) caused by loss of function variants in either of two genes involved in the regulation of histone methylation, KMT2D (34-76%) or KDM6A (9-13%). Previously, representative neurobehavioral deficits of KS were recapitulated in a mouse model, emphasizing the role of KMT2D in brain development, specifically in ongoing hippocampal neurogenesis in the granule cell layer of the dentate gyrus. Interestingly, anxiety, a phenotype that has a known association with decreased hippocampal neurogenesis, has been anecdotally reported in individuals with KS. In this study, anxiety and behavior were assessed in a cohort of 60 individuals with molecularly confirmed KS and 25 unaffected biological siblings, via questionnaires (SCARED/GAS-ID and CBCL/ABCL). Participant age ranged from 4 to 43 years old, with 88.3% of participants having a pathogenic variant in KMT2D, and the rest having variants in KDM6A. In addition, data was collected on adaptive function and positive affect/quality of life in participants with KS using appropriate online surveys including ABAS-III and PROMIS Positive Affect. Survey scores were compared within the KS participants across age groups and between KS participants and their unaffected siblings. We found that children with KS have significantly higher anxiety scores and total behavior problem scores than their unaffected siblings (p = 0.0225, p < 0.0001). Moreover, a large proportion of affected individuals (22.2% of children and 60.0% of adults) surpassed the established threshold for anxiety; this may even be an underestimate given many patients are already treated for anxiety. In this sample, anxiety levels did not correlate with level of cognitive or adaptive function in any KS participants, but negatively correlated with positive affect in children with KS (p = 0.0005). These findings indicate that anxiety is a common neurobehavioral feature of KS. Providers should therefore carefully screen individuals with KS for anxiety as well as other behavioral issues in order to allow for prompt intervention. Neurobehavioral anxiety measures may also prove to be important outcome measures for clinical trials in KS.

Sleep disturbance is a common feature of Kabuki syndrome.

Kabuki syndrome (KS) is a rare epigenetic disorder caused by heterozygous loss of function variants in either KMT2D (90%) or KDM6A (10%), both involved in regulation of histone methylation. While sleep disturbance in other Mendelian disorders of the epigenetic machinery has been reported, no study has been conducted on sleep in KS. This study assessed sleep in 59 participants with KS using a validated sleep questionnaire. Participants ranged in age from 4 to 43 years old with 86% of participants having a pathogenic variant in KMT2D. In addition, data on adaptive function, behavior, anxiety, and quality of life were collected using their respective questionnaires. Some form of sleep issue was present in 71% of participants, with night-waking, daytime sleepiness, and sleep onset delay being the most prevalent. Sleep dysfunction was positively correlated with maladaptive behaviors, anxiety levels, and decreasing quality of life. Sleep issues were not correlated with adaptive function. This study establishes sleep disturbance as a common feature of KS. Quantitative sleep measures may be a useful outcome measure for clinical trials in KS. Further, clinicians caring for those with KS should consider sleep dysfunction as an important feature that impacts overall health and well being in these patients.

Elevated H3K4me3 Through MLL2-WDR82 upon Hyperglycemia Causes Jagged Ligand Dependent Notch Activation to Interplay with Differentiation State of Endothelial Cells.

Endothelial-to-mesenchymal transition (EndMT) is a hallmark of diabetes-associated vascular complications. Epigenetic mechanisms emerged as one of the key pathways to regulate diabetes-associated complications. In the current study, we aimed to determine how abrupt changes in histone 3 lysine 4 tri-methylation (H3K4me3) upon hyperglycemia exposure reprograms endothelial cells to undergo EndMT. Through in vitro studies, we first establish that intermittent high-glucose exposure to EC most potently induced partial mesenchyme-like characteristics compared with transient or constant high-glucose-challenged endothelial cells. In addition, glomerular endothelial cells of BTBR Ob/Ob mice also exhibited mesenchymal-like characteristics. Intermittent hyperglycemia-dependent induction of partial mesenchyme-like phenotype of endothelial cells coincided with an increase in H3K4me3 level in both macro- and micro-vascular EC due to selective increase in MLL2 and WDR82 protein of SET1/COMPASS complex. Such an endothelial-specific heightened H3K4me3 level was also detected in intermittent high-glucose-exposed rat aorta and in kidney glomeruli of Ob/Ob mice. Elevated H3K4me3 enriched in the promoter regions of Notch ligands Jagged1 and Jagged2, thus causing abrupt expression of these ligands and concomitant activation of Notch signaling upon intermittent hyperglycemia challenge. Pharmacological inhibition and/or knockdown of MLL2 in cells in vitro or in tissues ex vivo normalized intermittent high-glucose-mediated increase in H3K4me3 level and further reversed Jagged1 and Jagged2 expression, Notch activation and further attenuated acquisition of partial mesenchyme-like phenotype of endothelial cells. In summary, the present study identifies a crucial role of histone methylation in hyperglycemia-dependent reprograming of endothelial cells to undergo mesenchymal transition and indicated that epigenetic pathways contribute to diabetes-associated vascular complications.

USP7 sustains an active epigenetic program via stabilizing MLL2 and WDR5 in diffuse large B-cell lymphoma.

Activated B-cell-like (ABC)-diffuse large B-cell lymphoma (ABC-DLBCL) is a common subtype of non-Hodgkin's lymphoma with poor prognosis. The survival of ABC-DLBCL relies on constitutive activation of BCR signaling, but the underlying molecular mechanism is not fully addressed. By mining The Cancer Genome Atlas database, we found that the expression of ubiquitin-specific protease 7 (USP7) is significantly elevated in three cancer types including DLBCL. Interestingly, unlike germinal center B-cell-like (GCB)-DLBCL, ABC-DLBCL shows upregulated expression of USP7. Inhibiting the enzymatic activity of USP7 (P22077) has a drastic effect on ABC-DLBCL, but not GCB-DLBCL cells. Compared to GCB-DLBCL, ABC-DLBCL cells show transcriptional upregulation of multiple components of BCR-signaling. USP7 inhibition significantly reduces the expression of upregulated components of BCR signaling. Mechanistically, USP7 inhibition greatly reduces the methylation of histone 3 on lysine 4 (H3K4me2), which is an epigenetic marker for active enhancers. USP7 inhibition greatly reduces the protein level of WDR5 and MLL2, key components of lysine-specific methyltransferase complex (complex of proteins associated with Set1 [COMPASS]). In ABC-DLBCL cells, USP7 stabilizes WDR5 and MLL2. In patients, the expression of USP7 is significantly associated with components of BCR signaling (LYN, SYK, BTK, PLCG2, PRKCB, MALT1, BCL10, and CARD11) and targets of BCR signaling (MYC and IRF4). In summary, we demonstrated an essential role of USP7 in ABC-DLBCL by organizing an oncogenic epigenetic program via stabilization of WDR5 and MLL2. Targeting USP7 might be a novel and efficient approach to treat patients with ABC-DLBCL and it might be better than targeting individual components such as BTK in BCR signaling.

Essential Functions of MLL1 and MLL2 in Retinal Development and Cone Cell Maintenance.

MLL1 (KMT2A) and MLL2 (KMT2B) are homologous members of the mixed-lineage leukemia (MLL) family of histone methyltransferases involved in epigenomic transcriptional regulation. Their sequence variants have been associated with neurological and psychological disorders, but little is known about their roles and mechanism of action in CNS development. Using mouse retina as a model, we previously reported MLL1's role in retinal neurogenesis and horizontal cell maintenance. Here we determine roles of MLL2 and MLL1/MLL2 together in retinal development using conditional knockout (CKO) mice. Deleting Mll2 from Chx10+ retinal progenitors resulted in a similar phenotype as Mll1 CKO, but removal of both alleles produced much more severe deficits than each single CKO: 1-month double CKO mutants displayed null light responses in electroretinogram; thin retinal layers, including shorter photoreceptor outer segments with impaired phototransduction gene expression; and reduced numbers of M-cones, horizontal and amacrine neurons, followed by fast retinal degeneration. Despite moderately reduced progenitor cell proliferation at P0, the neurogenic capacity was largely maintained in double CKO mutants. However, upregulated apoptosis and reactive gliosis were detected during postnatal retinal development. Finally, the removal of both MLLs in fated rods produced a normal phenotype, but the CKO in M-cones impaired M-cone function and survival, indicating both cell non-autonomous and autonomous mechanisms. Altogether, our results suggest that MLL1/MLL2 play redundant roles in maintaining specific retinal neurons after cell fate specification and are essential for establishing functional neural networks.

GRWD1-WDR5-MLL2 Epigenetic Complex Mediates H3K4me3 Mark and Is Essential for Kaposi's Sarcoma-Associated Herpesvirus-Induced Cellular Transformation.

Infection by Kaposi's sarcoma-associated herpesvirus (KSHV) is causally associated with numerous cancers. The mechanism of KSHV-induced oncogenesis remains unclear. By performing a CRISPR-Cas9 screening in a model of KSHV-induced cellular transformation of primary cells, we identified epigenetic regulators that were essential for KSHV-induced cellular transformation. Examination of TCGA data sets of the top 9 genes, including glutamate-rich WD repeat containing 1 (GRWD1), a WD40 family protein upregulated by KSHV, that had positive effects on cell proliferation and survival of KSHV-transformed cells (KMM) but not the matched primary cells (MM), uncovered the predictive values of their expressions for patient survival in numerous types of cancer. We revealed global epigenetic remodeling including H3K4me3 epigenetic active mark in KMM cells compared to MM cells. Knockdown of GRWD1 inhibited cell proliferation, cellular transformation, and tumor formation and caused downregulation of global H3K4me3 mark in KMM cells. GRWD1 interacted with WD repeat domain 5 (WDR5), the core protein of H3K4 methyltransferase complex, and several H3K4me3 methyltransferases, including myeloid leukemia 2 (MLL2). Knockdown of WDR5 and MLL2 phenocopied GRWD1 knockdown, caused global reduction of H3K4me3 mark, and altered the expression of similar sets of genes. Transcriptome sequencing (RNA-seq) and chromatin immunoprecipitation sequencing (ChIP-seq) analyses further identified common and distinct cellular genes and pathways that were regulated by GRWD1, WDR5, and MLL2. These results indicate that KSHV hijacks the GRWD1-WDR5-MLL2 epigenetic complex to regulate H3K4me3 methylation of specific genes, which is essential for KSHV-induced cellular transformation. Our work has identified an epigenetic complex as a novel therapeutic target for KSHV-induced cancers. IMPORTANCE By performing a genome-wide CRISPR-Cas9 screening, we have identified cellular epigenetic regulators that are essential for KSHV-induced cellular transformation. Among them, GRWD1 regulates epigenetic active mark H3K4me3 by interacting with WDR5 and MLL2 and recruiting them to chromatin loci of specific genes in KSHV-transformed cells. Hence, KSHV hijacks the GRWD1-WDR5-MLL2 complex to remodel cellular epigenome and induce cellular transformation. Since the dysregulation of GRWD1 is associated with poor prognosis in several types of cancer, GRWD1 might also be a critical driver in other viral or nonviral cancers.

LncRNA FOXP4-AS1 Promotes the Progression of Esophageal Squamous Cell Carcinoma by Interacting With MLL2/H3K4me3 to Upregulate FOXP4.

Malignant tumors are a grave threat to human health. Esophageal squamous cell carcinoma (ESCC) is a common gastrointestinal malignant tumor. China has a high incidence of ESCC, and its morbidity and mortality are higher than the global average. Increasingly, studies have shown that long noncoding RNAs (lncRNAs) play a vital function in the occurrence and development of tumors. Although the biological function of FOXP4-AS1 has been demonstrated in various tumors, the potential molecular mechanism of FOXP4-AS1 in ESCC is still poorly understood. The expression of FOXP4 and FOXP4-AS1 was detected in ESCC by quantitative real-time PCR (qRT-PCR) or SP immunohistochemistry (IHC). shRNA was used to silence gene expression. Apoptosis, cell cycle, MTS, colony formation, invasion and migration assays were employed to explore the biological functions of FOXP4 and FOXP4-AS1. The potential molecular mechanism of FOXP4-AS1 in ESCC was determined by dual-luciferase reporter, RNA immunoprecipitation (RIP) and chromatin immunoprecipitation (ChIP). Here, we demonstrated that FOXP4-AS1 was significantly increased in ESCC tissues and cell lines, associated with lymph node metastasis and TNM staging. Cell function experiments showed that FOXP4-AS1 promoted the proliferation, invasion and migration ability of ESCC cells. The expression of FOXP4-AS1 and FOXP4 in ESCC tissues was positively correlated. Further research found that FOXP4-AS1, upregulated in ESCC, promotes FOXP4 expression by enriching MLL2 and H3K4me3 in the FOXP4 promoter through a "molecular scaffold". Moreover, FOXP4, a transcription factor of ß-catenin, promotes the transcription of ß-catenin and ultimately leads to the malignant progression of ESCC. Finally, FOXP4-AS1 may be a new therapeutic target for ESCC.

Structure, Activity and Function of the MLL2 (KMT2B) Protein Lysine Methyltransferase.

The Mixed Lineage Leukemia 2 (MLL2) protein, also known as KMT2B, belongs to the family of mammalian histone H3 lysine 4 (H3K4) methyltransferases. It is a large protein of 2715 amino acids, widely expressed in adult human tissues and a paralog of the MLL1 protein. MLL2 contains a characteristic C-terminal SET domain responsible for methyltransferase activity and forms a protein complex with WRAD (WDR5, RbBP5, ASH2L and DPY30), host cell factors 1/2 (HCF 1/2) and Menin. The MLL2 complex is responsible for H3K4 trimethylation (H3K4me3) on specific gene promoters and nearby cis-regulatory sites, regulating bivalent developmental genes as well as stem cell and germinal cell differentiation gene sets. Moreover, MLL2 plays a critical role in development and germ line deletions of Mll2 have been associated with early growth retardation, neural tube defects and apoptosis that leads to embryonic death. It has also been involved in the control of voluntary movement and the pathogenesis of early stage childhood dystonia. Additionally, tumor-promoting functions of MLL2 have been detected in several cancer types, including colorectal, hepatocellular, follicular cancer and gliomas. In this review, we discuss the main structural and functional aspects of the MLL2 methyltransferase with particular emphasis on transcriptional mechanisms, gene regulation and association with diseases.

Metformin Reduces Histone H3K4me3 at the Promoter Regions of Positive Cell Cycle Regulatory Genes in Lung Cancer Cells.

This study aimed at understanding the effect of metformin on histone H3 methylation, DNA methylation, and chromatin accessibility in lung cancer cells. Metformin significantly reduced H3K4me3 level at the promoters of positive cell cycle regulatory genes such as CCNB2, CDK1, CDK6, and E2F8. Eighty-eight genes involved in cell cycle showed reduced H3K4me3 levels in response to metformin, and 27% of them showed mRNA downregulation. Metformin suppressed the expression of H3K4 methyltransferases MLL1, MLL2, and WDR82. The siRNA-mediated knockdown of MLL2 significantly downregulated global H3K4me3 level and inhibited lung cancer cell proliferation. MLL2 overexpression was found in 14 (33%) of 42 NSCLC patients, and a Cox proportional hazards analysis showed that recurrence-free survival of lung adenocarcinoma patients with MLL2 overexpression was approximately 1.32 (95% CI = 1.08-4.72; p = 0.02) times poorer than in those without it. Metformin showed little effect on DNA methylation and chromatin accessibility at the promoter regions of cell cycle regulatory genes. The present study suggests that metformin reduces H3K4me3 levels at the promoters of positive cell cycle regulatory genes through MLL2 downregulation in lung cancer cells. Additionally, MLL2 may be a potential therapeutic target for reducing the recurrence of lung adenocarcinoma.