Pathogenic variants in KMT2C result in a neurodevelopmental disorder distinct from Kleefstra and Kabuki syndromes.

Trithorax-related H3K4 methyltransferases, KMT2C and KMT2D, are critical epigenetic modifiers. Haploinsufficiency of KMT2C was only recently recognized as a cause of neurodevelopmental disorder (NDD), so the clinical and molecular spectrums of the KMT2C-related NDD (now designated as Kleefstra syndrome 2) are largely unknown. We ascertained 98 individuals with rare KMT2C variants, including 75 with protein-truncating variants (PTVs). Notably, ∼15% of KMT2C PTVs were inherited. Although the most highly expressed KMT2C transcript consists of only the last four exons, pathogenic PTVs were found in almost all the exons of this large gene. KMT2C variant interpretation can be challenging due to segmental duplications and clonal hematopoesis-induced artifacts. Using samples from 27 affected individuals, divided into discovery and validation cohorts, we generated a moderate strength disorder-specific KMT2C DNA methylation (DNAm) signature and demonstrate its utility in classifying non-truncating variants. Based on 81 individuals with pathogenic/likely pathogenic variants, we demonstrate that the KMT2C-related NDD is characterized by developmental delay, intellectual disability, behavioral and psychiatric problems, hypotonia, seizures, short stature, and other comorbidities. The facial module of PhenoScore, applied to photographs of 34 affected individuals, reveals that the KMT2C-related facial gestalt is significantly different from the general NDD population. Finally, using PhenoScore and DNAm signatures, we demonstrate that the KMT2C-related NDD is clinically and epigenetically distinct from Kleefstra and Kabuki syndromes. Overall, we define the clinical features, molecular spectrum, and DNAm signature of the KMT2C-related NDD and demonstrate they are distinct from Kleefstra and Kabuki syndromes highlighting the need to rename this condition.

KMT2D acetylation by CREBBP reveals a cooperative functional interaction at enhancers in normal and malignant germinal center B cells.

Heterozygous inactivating mutations of the KMT2D methyltransferase and the CREBBP acetyltransferase are among the most common genetic alterations in B cell lymphoma and co-occur in 40 to 60% of follicular lymphoma (FL) and 30% of EZB/C3 diffuse large B cell lymphoma (DLBCL) cases, suggesting they may be coselected. Here, we show that combined germinal center (GC)-specific haploinsufficiency of Crebbp and Kmt2d synergizes in vivo to promote the expansion of abnormally polarized GCs, a common preneoplastic event. These enzymes form a biochemical complex on select enhancers/superenhancers that are critical for the delivery of immune signals in the GC light zone and are only corrupted upon dual Crebbp/Kmt2d loss, both in mouse GC B cells and in human DLBCL. Moreover, CREBBP directly acetylates KMT2D in GC-derived B cells, and, consistently, its inactivation by FL/DLBCL-associated mutations abrogates its ability to catalyze KMT2D acetylation. Genetic and pharmacologic loss of CREBBP and the consequent decrease in KMT2D acetylation lead to reduced levels of H3K4me1, supporting a role for this posttranslational modification in modulating KMT2D activity. Our data identify a direct biochemical and functional interaction between CREBBP and KMT2D in the GC, with implications for their role as tumor suppressors in FL/DLBCL and for the development of precision medicine approaches targeting enhancer defects induced by their combined loss.

KMT2D regulates p63 target enhancers to coordinate epithelial homeostasis.

Epithelial tissues rely on a highly coordinated balance between self-renewal, proliferation, and differentiation, disruption of which may drive carcinogenesis. The epigenetic regulator KMT2D (MLL4) is one of the most frequently mutated genes in all cancers, particularly epithelial cancers, yet its normal function in these tissues is unknown. Here, we identify a novel role for KMT2D in coordinating this fine balance, as depletion of KMT2D from undifferentiated epidermal keratinocytes results in reduced proliferation, premature spurious activation of terminal differentiation genes, and disorganized epidermal stratification. Genome-wide, KMT2D interacts with p63 and is enriched at its target enhancers. Depletion of KMT2D results in a broad loss of enhancer histone modifications H3 Lys 4 (H3K4) monomethylation (H3K4me1) and H3K27 acetylation (H3K27ac) as well as reduced expression of p63 target genes, including key genes involved in epithelial development and adhesion. Together, these results reveal a critical role for KMT2D in the control of epithelial enhancers and p63 target gene expression, including the requirement of KMT2D for the maintenance of epithelial progenitor gene expression and the coordination of proper terminal differentiation.

The histone methyltransferase KMT2D maintains cellular glucocorticoid responsiveness by shielding the glucocorticoid receptor from degradation.

Because of their ability to induce lymphocyte apoptosis, glucocorticoids (GC) are widely used to treat hematological malignancies such as lymphomas and multiple myeloma. Their effectiveness is often limited, however, due to the development of glucocorticoid resistance by a variety of molecular mechanisms. Here we performed an unbiased genome-wide CRISPR screen with the human T-cell leukemia cell line Jurkat to find previously unidentified genes required for GC-induced apoptosis. One such gene was KMT2D (also known as MLL2 or MLL4), which encodes a histone lysine methyltransferase whose mutations are associated with a variety of cancers, blood malignancies in particular, and are considered markers of poor prognosis. Knockout of KMT2D by CRISPR/Cas9 gene editing in Jurkat and several multiple myeloma cell lines downregulated GR protein expression. Surprisingly, this was not due to a reduction in GR transcripts, but rather to a decrease in the protein's half-life, primarily due to proteasomal degradation. Reconstitution of KMT2D expression restored GR levels. In contrast to the known ability of KMT2D to control gene transcription through covalent histone methylation, KMT2D-mediated upregulation of GR levels did not require its methyltransferase activity. Co-immunoprecipitation and proximity ligation assays found constitutive binding of KMT2D to the GR, which was enhanced in the presence of GC. These observations reveal KMT2D to be essential for the stabilization of cellular GR levels, and suggest a possible mechanism by which KMT2D mutations may lead to GC resistance in some malignancies.

Exercise training alleviates cholesterol and lipid accumulation in mice with non-alcoholic steatohepatitis: reduction of KMT2D-mediated histone methylation of IDI1.

Exercise training is a cornerstone treatment for non-alcoholic fatty liver disease (NAFLD). This study aims to investigate the effects of exercises on lipid accumulation in non-alcoholic steatohepatitis (NASH) and to explore the molecular mechanism. Established NASH mice were remained sedentary or subjected to moderate-intensity continuous training or high-intensity interval training (HIIT). The two training regimens, especially the latter one, reduced liver weight, steatosis, inflammation, lipid accumulation, collagen deposition, and cholesterol content in the mouse liver. Similarly, the HIIT regimen improved clinical presentation of NAFLD patients. RNA sequencing analysis revealed lysine methyltransferase 2D (Kmt2d) and isopentenyl-diphosphate delta isomerase 1 (Idi1) as two important genes downregulated in mice underwent HIIT. By using mouse hepatocytes AML12, we found that KMT2D promoted Idi1 expression by catalyzing H3K4me1 modification near its promoter. Upregulation of either KMT2D or IDI1 blocked the ameliorating effects of HIIT on mice. Meanwhile, in AML12 cells modeled by palmitic acid and oleic acid treatment, KMT2D and IDI1 were found to be correlated with lipid accumulation, cholesterol content, inflammation, and cell death and senescence. In conclusion, this study demonstrates that the ameliorating effects of exercise training on NASH might involve the downregulation of the KMT2D/IDI1 axis.

Mll3 and Mll4 Facilitate Enhancer RNA Synthesis and Transcription from Promoters Independently of H3K4 Monomethylation.

Monomethylation of histone H3 at lysine 4 (H3K4me1) and acetylation of histone H3 at lysine 27 (H3K27ac) are correlated with transcriptionally engaged enhancer elements, but the functional impact of these modifications on enhancer activity is not well understood. Here we used CRISPR/Cas9 genome editing to separate catalytic activity-dependent and independent functions of Mll3 (Kmt2c) and Mll4 (Kmt2d, Mll2), the major enhancer H3K4 monomethyltransferases. Loss of H3K4me1 from enhancers in Mll3/4 catalytically deficient cells causes partial reduction of H3K27ac, but has surprisingly minor effects on transcription from either enhancers or promoters. In contrast, loss of Mll3/4 proteins leads to strong depletion of enhancer Pol II occupancy and eRNA synthesis, concomitant with downregulation of target genes. Interestingly, downregulated genes exhibit reduced polymerase levels in gene bodies, but not at promoters, suggestive of pause-release defects. Altogether, our results suggest that enhancer H3K4me1 provides only a minor contribution to the long-range coactivator function of Mll3/4.

A UTX-MLL4-p300 Transcriptional Regulatory Network Coordinately Shapes Active Enhancer Landscapes for Eliciting Transcription.

Enhancer activation is a critical step for gene activation. Here we report an epigenetic crosstalk at enhancers between the UTX (H3K27 demethylase)-MLL4 (H3K4 methyltransferase) complex and the histone acetyltransferase p300. We demonstrate that UTX, in a demethylase activity-independent manner, facilitates conversion of inactive enhancers in embryonic stem cells to an active (H3K4me1+/H3K27ac+) state by recruiting and coupling the enzymatic functions of MLL4 and p300. Loss of UTX leads to attenuated enhancer activity, characterized by reduced levels of H3K4me1 and H3K27ac as well as impaired transcription. The UTX-MLL4 complex enhances p300-dependent H3K27 acetylation through UTX-dependent stimulation of p300 recruitment, while MLL4-mediated H3K4 monomethylation, reciprocally, requires p300 function. Importantly, MLL4-generated H3K4me1 further enhances p300-dependent transcription. This work reveals a previously unrecognized cooperativity among enhancer-associated chromatin modulators, including a unique function for UTX, in establishing an "active enhancer landscape" and defines a detailed mechanism for the joint deposition of H3K4me1 and H3K27ac.

Abnormal Immune Profile in Individuals with Kabuki Syndrome.

OBJECTIVE: To analyze the lymphocyte subsets in individuals with Kabuki syndrome for better characterizing the immunological phenotype of this rare congenital disorder. METHODS: We characterized the immunological profile including B-, T- and natural killer-cell subsets in a series (N = 18) of individuals with Kabuki syndrome. RESULTS: All 18 individuals underwent genetic analysis: 15 had a variant in KMT2D and 3 a variant in KDM6A. Eleven of the 18 individuals (61%) had recurrent infections and 9 (50%) respiratory infections. Three (17%) had autoimmune diseases. On immunological analysis, 6 (33%) had CD4 T-cell lymphopenia, which was preferentially associated with the KMT2D truncating variant (5/9 individuals). Eight of 18 individuals (44%) had a humoral deficiency and eight (44%) had B lymphopenia. We found abnormal distributions of T-cell subsets, especially a frequent decrease in recent thymic emigrant CD4 + naive T-cell count in 13/16 individuals (81%). CONCLUSION: The immunological features of Kabuki syndrome showed variable immune disorders with CD4 + T-cell deficiency in one third of cases, which had not been previously reported. In particular, we found a reduction in recent thymic emigrant naïve CD4 + T-cell count in 13 of 16 individuals, representing a novel finding that had not previously been reported.

Craniosynostosis in molecularly diagnosed Kabuki syndrome: Prevalence and clinical implications.

Kabuki syndrome (KS) is characterized by growth impairment, psychomotor delay, congenital heart disease, and distinctive facial features. KMT2D and KDM6A have been identified as the causative genes of KS. Craniosynostosis (CS) has been reported in individuals with KS; however, its prevalence and clinical implications remain unclear. In this retrospective study, we investigated the occurrence of CS in individuals with genetically diagnosed KS and examined its clinical significance. Among 42 individuals with genetically diagnosed KS, 21 (50%) exhibited CS, with 10 individuals requiring cranioplasty. No significant differences were observed based on sex, causative gene, and molecular consequence among individuals with KS who exhibited CS. Both individuals who underwent evaluation with three-dimensional computed tomography (3DCT) and those who required surgery tended to exhibit cranial dysmorphology. Notably, in several individuals, CS was diagnosed before KS, suggesting that CS could be one of the clinical features by which clinicians can diagnose KS. This study highlights that CS is one of the noteworthy complications in KS, emphasizing the importance of monitoring cranial deformities in the health management of individuals with KS. The findings suggest that in individuals where CS is a concern, conducting 3DCT evaluations for CS and digital impressions are crucial.

Human Genetics of Atrial Septal Defect.

Although atrial septal defects (ASD) can be subdivided based on their anatomical location, an essential aspect of human genetics and genetic counseling is distinguishing between isolated and familiar cases without extracardiac features and syndromic cases with the co-occurrence of extracardiac abnormalities, such as developmental delay. Isolated or familial cases tend to show genetic alterations in genes related to important cardiac transcription factors and genes encoding for sarcomeric proteins. By contrast, the spectrum of genes with genetic alterations observed in syndromic cases is diverse. Currently, it points to different pathways and gene networks relevant to the dysregulation of cardiomyogenesis and ASD pathogenesis. Therefore, this chapter reflects the current knowledge and highlights stable associations observed in human genetics studies. It gives an overview of the different types of genetic alterations in these subtypes, including common associations based on genome-wide association studies (GWAS), and it highlights the most frequently observed syndromes associated with ASD pathogenesis.

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.

Mutation of cancer driver MLL2 results in transcription stress and genome instability.

Genome instability is a recurring feature of tumorigenesis. Mutation in MLL2, encoding a histone methyltransferase, is a driver in numerous different cancer types, but the mechanism is unclear. Here, we present evidence that MLL2 mutation results in genome instability. Mouse cells in which MLL2 gene deletion can be induced display elevated levels of sister chromatid exchange, gross chromosomal aberrations, 53BP1 foci, and micronuclei. Human MLL2 knockout cells are characterized by genome instability as well. Interestingly, MLL2 interacts with RNA polymerase II (RNAPII) and RECQL5, and, although MLL2 mutated cells have normal overall H3K4me levels in genes, nucleosomes in the immediate vicinity of RNAPII are hypomethylated. Importantly, MLL2 mutated cells display signs of substantial transcription stress, and the most affected genes overlap with early replicating fragile sites, show elevated levels of γH2AX, and suffer frequent mutation. The requirement for MLL2 in the maintenance of genome stability in genes helps explain its widespread role in cancer and points to transcription stress as a strong driver in tumorigenesis.

Unveiling the Molecular Landscape of Pancreatic Ductal Adenocarcinoma: Insights into the Role of the COMPASS-like Complex.

Pancreatic ductal adenocarcinoma (PDAC) is poised to become the second leading cause of cancer-related death by 2030, necessitating innovative therapeutic strategies. Genetic and epigenetic alterations, including those involving the COMPASS-like complex genes, have emerged as critical drivers of PDAC progression. This review explores the genetic and epigenetic landscape of PDAC, focusing on the role of the COMPASS-like complex in regulating chromatin accessibility and gene expression. Specifically, we delve into the functions of key components such as KDM6A, KMT2D, KMT2C, KMT2A, and KMT2B, highlighting their significance as potential therapeutic targets. Furthermore, we discuss the implications of these findings for developing novel treatment modalities for PDAC.

Lpt, trr, and Hcf regulate histone mono- and dimethylation that are essential for Drosophila heart development.

Mammalian KMT2C, KMT2D, and HCFC1 are expressed during heart development and have been associated with congenital heart disease, but their roles in heart development remain elusive. We found that the Drosophila Lpt and trr genes encode the N-terminal and C-terminal homologs, respectively, of mammalian KMT2C or KMT2D. Lpt and trr mutant embryos showed reduced cardiac progenitor cells. Silencing of Lpt, trr, or both simultaneously in the heart led to similar abnormal cardiac morphology, tissue fibrosis, and cardiac functional defects. Like KMT2D, Lpt and trr were found to modulate histone H3K4 mono- and dimethylation, but not trimethylation. Investigation of downstream genes regulated by mouse KMT2D in the heart showed that their fly homologs are similarly regulated by Lpt or trr in the fly heart, suggesting that Lpt and trr regulate an evolutionarily conserved transcriptional network for heart development. Moreover, we showed that cardiac silencing of Hcf, the fly homolog of mammalian HCFC1, leads to heart defects similar to those observed in Lpt and trr silencing, as well as reduced H3K4 monomethylation. Our findings suggest that Lpt and trr function together to execute the conserved function of mammalian KMT2C and KMT2D in histone H3 lysine K4 mono- and dimethylation required for heart development. Possibly aided by Hcf, which we show plays a related role in H3K4 methylation during fly heart development.

Unmasking the challenges of Kabuki syndrome in adulthood: A case series.

Kabuki syndrome is a recognizable Mendelian disorder characterized by the clinical constellation of childhood hypotonia, developmental delay or intellectual impairment, and characteristic dysmorphism resulting from monoallelic pathogenic variants in KMT2D or KDM6A. In the medical literature, most reported patients are children, and data is lacking on the natural history of the condition across the lifespan, with little known about adult-specific presentations and symptoms. Here, we report the results of a retrospective chart review of eight adult patients with Kabuki syndrome, seven of whom are molecularly confirmed. We use their trajectories to highlight the diagnostic challenges unique to an adult population, expand on neurodevelopmental/psychiatric phenotypes across the lifespan, and describe adult-onset medical complications, including a potential cancer risk and unusual and striking premature/accelerated aging phenotype.

Case report: Rare case of donor cell-derived T-cell acute lymphoblastic leukaemia in a female patient after receiving an allo-transplant from her male sibling.

Donor-derived haematological neoplasms, in which recipients present with haematological malignancies that have evolved from transplant donor stem cells, have previously been described for myelodysplastic syndrome, myeloproliferative neoplasms, acute myeloid leukaemia and less often, leukaemias of lymphoid origin. Here we describe a rare and complex case of donor-derived T-cell acute lymphoblastic leukaemia with a relatively short disease latency of less than 4 years. Through genomic and in vitro analyses, we identified novel mutations in NOTCH1 as well as a novel activating mutation in STAT5B; the latter targetable with the clinically available drugs, venetoclax and ruxolitinib.

Histone methyltransferase KMT2D promotes prostate cancer progression through paracrine IL-6 signaling.

Histone methyltransferase KMT2D plays a critical role as a human oncogene in prostate cancer (PCa). Dysregulated inflammatory responses and cytokine signaling are implicated in cancer progression. Furthermore, interleukin 6 (IL-6) is a pleiotropic cytokine that contributes to PCa progression; however, the association between KMT2D and IL-6 in PCa remains unclear. PCa cell proliferative potential, migratory potential, and apoptosis in vitro were determined using cell counting kit-8 (CCK-8), EdU incorporation, wound healing, and apoptosis assays. Proliferation and migratory potential were impaired and apoptosis was induced in PCa cells cultured with the conditioned medium from KMT2D-depleted cells. Cytokine array analysis showed that IL-6 was the most affected cytokine in the conditioned media. KMT2D knockdown significantly downregulated the expression of IL-6 in PCa cells. What's more, proliferation and migration were also impaired and apoptosis was also induced by silencing IL-6R expression. Immunohistochemistry (IHC) and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) were performed to validate the positive correlation between KMT2D and IL-6 in PCa tissue samples. Chromatin immunoprecipitation (ChIP)-PCR demonstrated that KMT2D and H3K4me1 occupied IL-6 enhancer regions and therefore, directly regulated IL-6 expression. The present study revealed that the KMT2D knockdown suppressed prostate cancer progression through the downregulation of paracrine IL-6 signaling. These results suggest that KMT2D could be regarded as a potential new target for PCa therapy.

The KMT2D Kabuki syndrome histone methylase controls neural crest cell differentiation and facial morphology.

Kabuki syndrome (KS) is a congenital craniofacial disorder resulting from mutations in the KMT2D histone methylase (KS1) or the UTX histone demethylase (KS2). With small cohorts of KS2 patients, it is not clear whether differences exist in clinical manifestations relative to KS1. We mutated KMT2D in neural crest cells (NCCs) to study cellular and molecular functions in craniofacial development with respect to UTX. Similar to UTX, KMT2D NCC knockout mice demonstrate hypoplasia with reductions in frontonasal bone lengths. We have traced the onset of KMT2D and UTX mutant NCC frontal dysfunction to a stage of altered osteochondral progenitor differentiation. KMT2D NCC loss-of-function does exhibit unique phenotypes distinct from UTX mutation, including fully penetrant cleft palate, mandible hypoplasia and deficits in cranial base ossification. KMT2D mutant NCCs lead to defective secondary palatal shelf elevation with reduced expression of extracellular matrix components. KMT2D mutant chondrocytes in the cranial base fail to properly differentiate, leading to defective endochondral ossification. We conclude that KMT2D is required for appropriate cranial NCC differentiation and KMT2D-specific phenotypes may underlie differences between Kabuki syndrome subtypes.

DNA methylation signature classification of rare disorders using publicly available methylation data.

Disease-specific DNA methylation patterns (DNAm signatures) have been established for an increasing number of genetic disorders and represent a valuable tool for classification of genetic variants of uncertain significance (VUS). Sample size and batch effects are critical issues for establishing DNAm signatures, but their impact on the sensitivity and specificity of an already established DNAm signature has not previously been tested. Here, we assessed whether publicly available DNAm data can be employed to generate a binary machine learning classifier for VUS classification, and used variants in KMT2D, the gene associated with Kabuki syndrome, together with an existing DNAm signature as proof-of-concept. Using publicly available methylation data for training, a classifier for KMT2D variants was generated, and individuals with molecularly confirmed Kabuki syndrome and unaffected individuals could be correctly classified. The present study documents the clinical utility of a robust DNAm signature even for few affected individuals, and most importantly, underlines the importance of data sharing for improved diagnosis of rare genetic disorders.

Treatment of immune thrombocytopenia with hetrombopag olamine tablets in a Kabuki syndrome patient with new KMT2D mutations.

Kabuki syndrome (KS) is a rare multisystem-affecting genetic disorder, and usually accompanied with autoimmune disorders such as immune thrombocytopenic purpura (ITP). Here, we report a 16-year-old patient with Kabuki syndrome with ITP and observe the therapeutic effect of TPO agonist hetrombopag olamine tablets. The duration of maintenance therapy and follow up were both 17 months. Whole exon sequencing (WES) of the patient's peripheral blood showed c.5775_5778del (p. Leu1926LysfsTer120) heterozygous mutation in the KMT2D gene, which was not reported before.