Polycomb dysregulation in gliomagenesis targets a Zfp423-dependent differentiation network

Increased prostaglandin-D2 in male STAT3-deficient hearts shifts cardiac progenitor cells from endothelial to white adipocyte differentiation

Cardiac levels of the signal transducer and activator of transcription factor-3 (STAT3) decline with age, and male but not female mice with a cardiomyocyte-specific STAT3 deficiency conditional knockout (CKO) display premature age-related heart failure associated with reduced cardiac capillary density. In the present study, isolated male and female CKO-cardiomyocytes exhibit increased prostaglandin (PG)-generating cyclooxygenase-2 (COX-2) expression. The PG-degrading hydroxyprostaglandin-dehydrogenase-15 (HPGD) expression is only reduced in male cardiomyocytes, which is associated with increased prostaglandin D₂ (PGD₂) secretion from isolated male but not female CKO-cardiomyocytes. Reduced HPGD expression in male cardiomyocytes derive from impaired androgen receptor (AR)–signaling due to loss of its cofactor STAT3. Elevated PGD₂ secretion in males is associated with increased white adipocyte accumulation in aged male but not female hearts. Adipocyte differentiation is enhanced in isolated stem cell antigen-1 (SCA-1)⁺ cardiac progenitor cells (CPC) from young male CKO-mice compared with the adipocyte differentiation of male wild-type (WT)-CPC and CPC isolated from female mice. Epigenetic analysis in freshly isolated male CKO-CPC display hypermethylation in pro-angiogenic genes (Fgfr2, Epas1) and hypomethylation in the white adipocyte differentiation gene Zfp423 associated with up-regulated ZFP423 expression and a shift from endothelial to white adipocyte differentiation compared with WT-CPC. The expression of the histone-methyltransferase EZH2 is reduced in male CKO-CPC compared with male WT-CPC, whereas no differences in the EZH2 expression in female CPC were observed. Clonally expanded CPC can differentiate into endothelial cells or into adipocytes depending on the differentiation conditions. ZFP423 overexpression is sufficient to induce white adipocyte differentiation of clonal CPC. In isolated WT-CPC, PGD₂ stimulation reduces the expression of EZH2, thereby up-regulating ZFP423 expression and promoting white adipocyte differentiation. The treatment of young male CKO mice with the COX inhibitor Ibuprofen or the PGD₂ receptor (DP)2 receptor antagonist BAY-u 3405 in vivo increased EZH2 expression and reduced ZFP423 expression and adipocyte differentiation in CKO-CPC. Thus, cardiomyocyte STAT3 deficiency leads to age-related and sex-specific cardiac remodeling and failure in part due to sex-specific alterations in PGD₂ secretion and subsequent epigenetic impairment of the differentiation potential of CPC. Causally involved is the impaired AR signaling in absence of STAT3, which reduces the expression of the PG-degrading enzyme HPGD.

Impaired androgen-receptor-signaling due to STAT3-deficiency promotes increased prostaglandin-D2-secretion from male but not female cardiomyocytes; this induces an epigenetic switch in cardiac progenitor cells from endothelial to white adipocyte differentiation, associated with reduced cardiac capillary density, increased cardiac white fat deposits and heart failure in aged male but not female mice.

Sox2-dependent maintenance of mouse oligodendroglioma involves the Sox2-mediated downregulation of Cdkn2b, Ebf1, Zfp423, and Hey2

Cancer stem cells (CSC) are essential for tumorigenesis. The transcription factor Sox2 is overexpressed in brain gliomas, and is essential to maintain CSC. In mouse high-grade glioma pHGG cells in culture, Sox2 deletion causes cell proliferation arrest and inability to reform tumors after transplantation in vivo; in Sox2-deleted cells, 134 genes are derepressed. To identify genes mediating Sox2 deletion effects, we overexpressed into pHGG cells nine among the most derepressed genes, and identified four genes, Ebf1, Hey2, Zfp423, and Cdkn2b, that strongly reduced cell proliferation in vitro and brain tumorigenesis in vivo. CRISPR/Cas9 mutagenesis of each gene, individually or in combination (Ebf1 + Cdkn2b), significantly antagonized the proliferation arrest caused by Sox2 deletion. The same genes also repressed clonogenicity in primary human glioblastoma-derived CSC-like lines. These experiments identify a network of critical tumor suppressive Sox2-targets whose inhibition by Sox2 is involved in glioma CSC maintenance, defining new potential therapeutic targets.

ZNF423 patient variants, truncations, and in-frame deletions in mice define an allele-dependent range of midline brain abnormalities

Interpreting rare variants remains a challenge in personal genomics, especially for disorders with several causal genes and for genes that cause multiple disorders. ZNF423 encodes a transcriptional regulatory protein that intersects several developmental pathways. ZNF423 has been implicated in rare neurodevelopmental disorders, consistent with midline brain defects in Zfp423-mutant mice, but pathogenic potential of most patient variants remains uncertain. We engineered ~50 patient-derived and small deletion variants into the highly-conserved mouse ortholog and examined neuroanatomical measures for 791 littermate pairs. Three substitutions previously asserted pathogenic appeared benign, while a fourth was effectively null. Heterozygous premature termination codon (PTC) variants showed mild haploabnormality, consistent with loss-of-function intolerance inferred from human population data. In-frame deletions of specific zinc fingers showed mild to moderate abnormalities, as did low-expression variants. These results affirm the need for functional validation of rare variants in biological context and demonstrate cost-effective modeling of neuroanatomical abnormalities in mice.

The Chromatin Environment Around Interneuron Genes in Oligodendrocyte Precursor Cells and Their Potential for Interneuron Reprograming

Oligodendrocyte precursor cells (OPCs), also known as NG2 glia, arise from neural progenitor cells in the embryonic ganglionic eminences that also generate inhibitory neurons. They are ubiquitously distributed in the central nervous system, remain proliferative through life, and generate oligodendrocytes in both gray and white matter. OPCs exhibit some lineage plasticity, and attempts have been made to reprogram them into neurons, with varying degrees of success. However, little is known about how epigenetic mechanisms affect the ability of OPCs to undergo fate switch and whether OPCs have a unique chromatin environment around neuronal genes that might contribute to their lineage plasticity. Our bioinformatic analysis of histone posttranslational modifications at interneuron genes in OPCs revealed that OPCs had significantly fewer bivalent and repressive histone marks at interneuron genes compared to astrocytes or fibroblasts. Conversely, OPCs had a greater degree of deposition of active histone modifications at bivalently marked interneuron genes than other cell types, and this was correlated with higher expression levels of these genes in OPCs. Furthermore, a significantly higher proportion of interneuron genes in OPCs than in other cell types lacked the histone posttranslational modifications examined. These genes had a moderately high level of expression, suggesting that the "no mark" interneuron genes could be in a transcriptionally "poised" or "transitional" state. Thus, our findings suggest that OPCs have a unique histone code at their interneuron genes that may obviate the need for erasure of repressive marks during their fate switch to inhibitory neurons.

Gene-based analysis in HRC imputed genome wide association data identifies three novel genes for Alzheimer's disease

Late onset Alzheimer's disease is the most common form of dementia for which about 30 susceptibility loci have been reported. The aim of the current study is to identify novel genes associated with Alzheimer's disease using the largest up-to-date reference single nucleotide polymorphism (SNP) panel, the most accurate imputation software and a novel gene-based analysis approach which tests for patterns of association within genes, in the powerful genome-wide association dataset of the International Genomics of Alzheimer's Project Consortium, comprising over 7 million genotypes from 17,008 Alzheimer's cases and 37,154 controls. In addition to earlier reported genes, we detected three novel gene-wide significant loci PPARGC1A (p = 2.2 × 10-6), RORA (p = 7.4 × 10-7) and ZNF423 (p = 2.1 × 10-6). PPARGC1A and RORA are involved in circadian rhythm; circadian disturbances are one of the earliest symptoms of Alzheimer's disease. PPARGC1A is additionally linked to energy metabolism and the generation of amyloid beta plaques. RORA is involved in a variety of functions apart from circadian rhythm, such as cholesterol metabolism and inflammation. The ZNF423 gene resides in an Alzheimer's disease-specific protein network and is likely involved with centrosomes and DNA damage repair.

Transcriptional brakes on the road to adipocyte thermogenesis

White adipocytes represent the principle site for energy storage whereas brown/beige adipocytes emerge from seemingly distinct cellular lineages and burn chemical energy to produce heat. Thermogenic adipocytes utilize cell-type selective master regulatory transcription factors to drive the expression of their adipocyte thermogenic gene program. White adipocytes harbor transcriptional mechanisms to suppress the thermogenic gene program and maintain an energy-storing function. Here, we summarize some of the key developmental and transcriptional mechanisms leading to the postnatal recruitment of thermogenic adipocytes under physiological conditions, with a particular emphasis on the transcriptional "brakes" on the thermogenic gene program. We highlight a number of recent studies, including our own work on the transcription factor, ZFP423, that illustrate the potential to engineer the subcutaneous and visceral white fat lineages to adopt a thermogenic fat cell fate by releasing the inhibition of the adipocyte thermogenic gene program. These transcriptional brakes on adipocyte thermogenesis may represent potential targets of therapeutic interventions designed to combat obesity and associated metabolic disorders.

ZNF423: A New Player in Estrogen Receptor-Positive Breast Cancer

Preventive therapy can target hormone-responsive breast cancer (BC) by treatment with selective estrogen receptor modulators (SERMs) and reduce the incidence of BC. Genome-wide association studies have identified single nucleotide polymorphisms (SNPs) with relevant predictive values, SNPs in the ZNF423 gene were associated with decreased risk of BC during SERM therapy, and SNPs in the Cathepsin O gene with an increased risk. ZNF423, which was not previously associated with BC is a multifunctional transcription factor known to have a role in development, neurogenesis, and adipogenesis and is implicated in other types of cancer. ZNF423 is transcriptionally controlled by the homolog ZNF521, early B cell factor transcription factor, epigenetic silencing of the promoter by CpG island hyper-methylation, and also by ZNF423 itself in an auto-regulatory loop. In BC cells, ZNF423 expression is found to be induced by estrogen, dependent on the binding of the estrogen receptor and calmodulin-like 3 to SNPs in ZNP423 intronic sites in proximity to consensus estrogen response elements. ZNF423 has also been shown to play a mechanistic role by trans-activating the tumor suppressor BRCA1 and thus modulating the DNA damage response. Even though recent extensive trial studies did not classify these SNPs with the highest predictive values, for inclusion in polygenic SNP analysis, the mechanism unveiled in these studies has introduced ZNF423 as a factor important in the control of the estrogen response. Here, we aim at providing an overview of ZNF423 expression and functional role in human malignancies, with a specific focus on its implication in hormone-responsive BC.

ING5 activity in self-renewal of glioblastoma stem cells via calcium and follicle stimulating hormone pathways

Stem cell-like brain tumor initiating cells (BTICs) cause recurrence of glioblastomas, with BTIC 'stemness' affected by epigenetic mechanisms. The ING family of epigenetic regulators (ING1-5) function by targeting histone acetyltransferase (HAT) or histone deacetylase complexes to the H3K4me3 mark to alter histone acetylation and subsequently, gene expression. Here we find that ectopic expression of ING5, the targeting subunit of HBO1, MOZ and MORF HAT complexes increases expression of the Oct4, Olig2 and Nestin stem cell markers, promotes self-renewal, prevents lineage differentiation and increases stem cell pools in BTIC populations. This activity requires the plant homeodomain region of ING5 that interacts specifically with the H3K4me3 mark. ING5 also enhances PI3K/AKT and MEK/ERK activity to sustain self-renewal of BTICs over serial passage of stem cell-like spheres. ING5 exerts these effects by activating transcription of calcium channel and follicle stimulating hormone pathway genes. In silico analyses of The Cancer Genome Atlas data suggest that ING5 is a positive regulator of BTIC stemness, whose expression negatively correlates with patient prognosis, especially in the Proneural and Classical subtypes, and in tumors with low SOX2 expression. These data suggest that altering histone acetylation status and signaling pathways induced by ING5 may provide useful clinical strategies to target tumor resistance and recurrence in glioblastoma.

Control of multidimensional systems on complex network

Multidimensional systems coupled via complex networks are widespread in nature and thus frequently invoked for a large plethora of interesting applications. From ecology to physics, individual entities in mutual interactions are grouped in families, homogeneous in kind. These latter interact selectively, through a sequence of self-consistently regulated steps, whose deeply rooted architecture is stored in the assigned matrix of connections. The asymptotic equilibrium eventually attained by the system, and its associated stability, can be assessed by employing standard nonlinear dynamics tools. For many practical applications, it is however important to externally drive the system towards a desired equilibrium, which is resilient, hence stable, to external perturbations. To this end we here consider a system made up of N interacting populations which evolve according to general rate equations, bearing attributes of universality. One species is added to the pool of interacting families and used as a dynamical controller to induce novel stable equilibria. Use can be made of the root locus method to shape the needed control, in terms of intrinsic reactivity and adopted protocol of injection. The proposed method is tested on both synthetic and real data, thus enabling to demonstrate its robustness and versatility.

Therapeutic Potential for Bone Morphogenetic Protein 4 in Human Malignant Glioma

Human glioma, in particular, malignant forms such as glioblastoma exhibit dismal survival rates despite advances in treatment strategies. A population of glioma cells with stem-like features, glioma cancer stem-like cells (GCSCs), contribute to renewal and maintenance of the tumor cell population and appear responsible for chemotherapeutic and radiation resistance. Bone morphogenetic protein 4 (BMP4), drives differentiation of GCSCs and thus improves therapeutic efficacy. Based on this observation it is imperative that the clinical merits of BMP4 in treating human gliomas should be addressed. This article reviews BMP4 signaling in central nervous system development and in glioma tumorigenesis, and the potential of this molecule as a treatment target in human gliomas. Further work needs to be done to determine if distinct lineages of GCSCs, associated with different glioma sub-classifications, proneural, neural, classical and mesenchymal, differ in responsiveness to BMP4 treatment. Additionally, interaction among BMP4 and cell matrix, tumor-vascular molecules and microglial immune cells also needs to be investigated, as this will enhance our knowledge about the role of BMP4 in human glioma and lead to the identification and/or development of novel therapeutic approaches that improve treatment outcomes of these devastating tumors.

Glioblastoma Stem-Like Cells: Characteristics, Microenvironment, and Therapy

Glioblastoma multiforme (GBM), grade IV astrocytoma, is the most fatal malignant primary brain tumor. GBM contains functional subsets of cells called glioblastoma stem-like cells (GSCs), which are radioresistant and chemoresistant and eventually lead to tumor recurrence. Recent studies showed that GSCs reside in particular tumor niches that are necessary to support their behavior. To successfully eradicate GBM growth and recurrence, new strategies selectively targeting GSCs and/or their microenvironmental niche should be designed. In this regard, here we focus on elucidating the molecular mechanisms that govern these GSC properties and on understanding the mechanism of the microenvironmental signals within the tumor mass. Moreover, to overcome the blood–brain barrier, which represents a critical limitation of GBM treatments, a new drug delivery system should be developed. Nanoparticles can be easily modified by different methods to facilitate delivery efficiency of chemotherapeutics, to enhance the accumulation within the tumors, and to promote the capacity for targeting the GSCs. Therefore, nanotechnology has become the most promising approach to GSC-targeting therapy. Additionally, we discussed the future of nanotechnology-based targeted therapy and point out the disadvantages that should be overcome.

Zfp423 Regulates Sonic Hedgehog Signaling via Primary Cilium Function

Zfp423 encodes a 30-zinc finger transcription factor that intersects several canonical signaling pathways. Zfp423 mutations result in ciliopathy-related phenotypes, including agenesis of the cerebellar vermis in mice and Joubert syndrome (JBTS19) and nephronophthisis (NPHP14) in humans. Unlike most ciliopathy genes, Zfp423 encodes a nuclear protein and its developmental expression is complex, leading to alternative proposals for cellular mechanisms. Here we show that Zfp423 is expressed by cerebellar granule cell precursors, that loss of Zfp423 in these precursors leads to cell-intrinsic reduction in proliferation, loss of response to Shh, and primary cilia abnormalities that include diminished frequency of both Smoothened and IFT88 localization. Loss of Zfp423 alters expression of several genes encoding key cilium components, including increased expression of Tulp3. Tulp3 is a direct binding target of Zfp423 and reducing the overexpression of Tulp3 in Zfp423-deficient cells suppresses Smoothened translocation defects. These results define Zfp423 deficiency as a bona fide ciliopathy, acting upstream of Shh signaling, and indicate a mechanism intrinsic to granule cell precursors for the resulting cerebellar hypoplasia.