scholarly journals Non-monotonic regulation of gene expression, neural progenitor fate and brain growth by the chromatin remodeller CHD8

2018 ◽  
Author(s):  
Shaun Hurley ◽  
Conor Mohan ◽  
Philipp Suetterlin ◽  
Jacob Ellegood ◽  
Fabrizio Rudari ◽  
...  
Keyword(s):  
Gene Expression ◽  
Brain Development ◽  
Protein Function ◽  
Target Genes ◽  
Regulation Of Gene Expression ◽  
Neural Progenitor ◽  
Dominant Negative ◽  
Brain Growth ◽  
Loss Of Function ◽  
Altered Expression

SummaryHeterozygous CHD8 mutations are associated with autism and macrocephaly with high penetrance in the human population. The reported mutations may have loss-of-function (haploinsufficient), hypomorphic or dominant negative effects on protein function. To determine the effects of reducing CHD8 protein function below haploinsufficient levels on brain development, we established a Chd8 allelic series in the mouse. Chd8 heterozygous mice exhibited relatively subtle brain overgrowth and little gene expression changes in the embryonic neocortex. In comparison, mild Chd8 hypomorphs displayed significant postnatal lethality, with surviving animals exhibiting more pronounced brain hyperplasia, and significantly altered expression of over 2000 genes. Autism-associated genes were downregulated and neural progenitor proliferation genes upregulated. Severe Chd8 hypomorphs displayed even greater transcriptional dysregulation, affecting genes and pathways that largely overlapped with those dysregulated in the mild hypomorphs. By contrast, homozygous, conditional deletion of Chd8 in early neuronal progenitors resulted in the induction of p53 target genes, cell cycle exit, apoptosis and pronounced brain hypoplasia. Intriguingly, increased progenitor proliferation in hypomorphs was primarily restricted to TBR2+ intermediate progenitors, suggesting critical roles for CHD8 in regulating the expansion of this population. Given the importance of these progenitors in human cortical growth, this observation suggests that human brain development might be more sensitive to CHD8 deficiency than the mouse. We conclude that brain development is acutely sensitive to CHD8 dosage and that the varying sensitivities of different progenitor populations and cellular processes to CHD8 dosage can result in non-linear effects on gene transcription and brain growth.

scholarly journals Maternal small RNAs mediate spatial-temporal regulation of gene expression, imprinting, and seed development in Arabidopsis

2019 ◽  
Vol 116 (7) ◽  
pp. 2761-2766 ◽  
Author(s):  
Ryan C. Kirkbride ◽  
Jie Lu ◽  
Changqing Zhang ◽  
Rebecca A. Mosher ◽  
David C. Baulcombe ◽  
...  
Keyword(s):  
Gene Expression ◽  
Seed Development ◽  
Seed Coat ◽  
Target Genes ◽  
Expression Patterns ◽  
Regulation Of Gene Expression ◽  
Small Interfering Rnas ◽  
Altered Expression ◽  
Temporal Regulation ◽  
Laser Capture

Arabidopsis seed development involves maternal small interfering RNAs (siRNAs) that induce RNA-directed DNA methylation (RdDM) through the NRPD1-mediated pathway. To investigate their biological functions, we characterized siRNAs in the endosperm and seed coat that were separated by laser-capture microdissection (LCM) in reciprocal genetic crosses with an nrpd1 mutant. We also monitored the spatial-temporal activity of the NRPD1-mediated pathway on seed development using the AGO4:GFP::AGO4 (promoter:GFP::protein) reporter and promoter:GUS sensors of siRNA-mediated silencing. From these approaches, we identified four distinct groups of siRNA loci dependent on or independent of the maternal NRPD1 allele in the endosperm or seed coat. A group of maternally expressed NRPD1-siRNA loci targets endosperm-preferred genes, including those encoding AGAMOUS-LIKE (AGL) transcription factors. Using translational promoter:AGL::GUS constructs as sensors, we demonstrate that spatial and temporal expression patterns of these genes in the endosperm are regulated by the NRPD1-mediated pathway irrespective of complete silencing (AGL91) or incomplete silencing (AGL40) of these target genes. Moreover, altered expression of these siRNA-targeted genes affects seed size. We propose that the corresponding maternal siRNAs could account for parent-of-origin effects on the endosperm in interploidy and hybrid crosses. These analyses reconcile previous studies on siRNAs and imprinted gene expression during seed development.

scholarly journals Human neurons from Christianson syndrome iPSCs reveal mutation-specific responses to rescue strategies

2021 ◽  
Vol 13 (580) ◽  
pp. eaaw0682
Author(s):  
Sofia B. Lizarraga ◽  
Li Ma ◽  
Abbie M. Maguire ◽  
Laura I. van Dyck ◽  
Qing Wu ◽  
...  
Keyword(s):  
Protein Function ◽  
Induced Pluripotent Stem Cell ◽  
Neurite Growth ◽  
Dominant Negative ◽  
Trophic Factors ◽  
Response To Treatment ◽  
Brain Growth ◽  
Loss Of Function ◽  
Treatment Development ◽  
Human Neurons

Christianson syndrome (CS), an X-linked neurological disorder characterized by postnatal attenuation of brain growth (postnatal microcephaly), is caused by mutations in SLC9A6, the gene encoding endosomal Na+/H+ exchanger 6 (NHE6). To hasten treatment development, we established induced pluripotent stem cell (iPSC) lines from patients with CS representing a mutational spectrum, as well as biologically related and isogenic control lines. We demonstrated that pathogenic mutations lead to loss of protein function by a variety of mechanisms: The majority of mutations caused loss of mRNA due to nonsense-mediated mRNA decay; however, a recurrent, missense mutation (the G383D mutation) had both loss-of-function and dominant-negative activities. Regardless of mutation, all patient-derived neurons demonstrated reduced neurite growth and arborization, likely underlying diminished postnatal brain growth in patients. Phenotype rescue strategies showed mutation-specific responses: A gene transfer strategy was effective in nonsense mutations, but not in the G383D mutation, wherein residual protein appeared to interfere with rescue. In contrast, application of exogenous trophic factors (BDNF or IGF-1) rescued arborization phenotypes across all mutations. These results may guide treatment development in CS, including gene therapy strategies wherein our data suggest that response to treatment may be dictated by the class of mutation.

scholarly journals Emerging Role of ODC1 in Neurodevelopmental Disorders and Brain Development

Genes ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 470
Author(s):  
Jeremy W. Prokop ◽  
Caleb P. Bupp ◽  
Austin Frisch ◽  
Stephanie M. Bilinovich ◽  
Daniel B. Campbell ◽  
...  
Keyword(s):  
Brain Development ◽  
Neural Progenitor Cells ◽  
Neurodevelopmental Disorder ◽  
Fetal Brain ◽  
Missense Variant ◽  
Neural Progenitor ◽  
Loss Of Function ◽  
Gain Of Function ◽  
Systematic Analysis ◽  
Function Expression

Ornithine decarboxylase 1 (ODC1 gene) has been linked through gain-of-function variants to a rare disease featuring developmental delay, alopecia, macrocephaly, and structural brain anomalies. ODC1 has been linked to additional diseases like cancer, with growing evidence for neurological contributions to schizophrenia, mood disorders, anxiety, epilepsy, learning, and suicidal behavior. The evidence of ODC1 connection to neural disorders highlights the need for a systematic analysis of ODC1 genotype-to-phenotype associations. An analysis of variants from ClinVar, Geno2MP, TOPMed, gnomAD, and COSMIC revealed an intellectual disability and seizure connected loss-of-function variant, ODC G84R (rs138359527, NC_000002.12:g.10444500C > T). The missense variant is found in ~1% of South Asian individuals and results in 2.5-fold decrease in enzyme function. Expression quantitative trait loci (eQTLs) reveal multiple functionally annotated, non-coding variants regulating ODC1 that associate with psychiatric/neurological phenotypes. Further dissection of RNA-Seq during fetal brain development and within cerebral organoids showed an association of ODC1 expression with cell proliferation of neural progenitor cells, suggesting gain-of-function variants with neural over-proliferation and loss-of-function variants with neural depletion. The linkage from the expression data of ODC1 in early neural progenitor proliferation to phenotypes of neurodevelopmental delay and to the connection of polyamine metabolites in brain function establish ODC1 as a bona fide neurodevelopmental disorder gene.

scholarly journals Distinct, dosage-sensitive requirements for the autism-associated factor CHD8 during cortical development

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shaun Hurley ◽  
Conor Mohan ◽  
Philipp Suetterlin ◽  
Robert Ellingford ◽  
Kimberley L. H. Riegman ◽  
...  
Keyword(s):  
Gene Expression ◽  
Brain Development ◽  
Brain Size ◽  
Cortical Development ◽  
Neural Progenitor ◽  
Conditional Knockout ◽  
P53 Pathway ◽  
Associated Factor ◽  
Transcriptional Dysregulation ◽  
Intermediate Progenitors

Abstract Background CHD8 haploinsufficiency causes autism and macrocephaly with high penetrance in the human population. Chd8 heterozygous mice exhibit relatively subtle brain overgrowth and little gene expression changes in the embryonic neocortex. The purpose of this study was to generate new, sub-haploinsufficient Chd8 mouse models to allow us to identify and study the functions of CHD8 during embryonic cortical development. Methods To examine the possibility that certain phenotypes may only appear at sub-heterozygous Chd8 levels in the mouse, we created an allelic series of Chd8-deficient mice to reduce CHD8 protein levels to approximately 35% (mild hypomorph), 10% (severe hypomorph) and 0% (neural-specific conditional knockout) of wildtype levels. We used RNA sequencing to compare transcriptional dysregulation, structural MRI and brain weight to investigate effects on brain size, and cell proliferation, differentiation and apoptosis markers in immunostaining assays to quantify changes in neural progenitor fate. Results Mild Chd8 hypomorphs displayed significant postnatal lethality, with surviving animals exhibiting more pronounced brain hyperplasia than heterozygotes. Over 2000 genes were dysregulated in mild hypomorphs, including autism-associated neurodevelopmental and cell cycle genes. We identify increased proliferation of non-ventricular zone TBR2+ intermediate progenitors as one potential cause of brain hyperplasia in these mutants. Severe Chd8 hypomorphs displayed even greater transcriptional dysregulation, including evidence for p53 pathway upregulation. In contrast to mild hypomorphs, these mice displayed reduced brain size and increased apoptosis in the embryonic neocortex. Homozygous, conditional deletion of Chd8 in early neuronal progenitors resulted in pronounced brain hypoplasia, partly caused by p53 target gene derepression and apoptosis in the embryonic neocortex. Limitations Our findings identify an important role for the autism-associated factor CHD8 in controlling the proliferation of intermediate progenitors in the mouse neocortex. We propose that CHD8 has a similar function in human brain development, but studies on human cells are required to confirm this. Because many of our mouse mutants with reduced CHD8 function die shortly after birth, it is not possible to fully determine to what extent reduced CHD8 function results in autism-associated behaviours in mice. Conclusions Together, these findings identify important, dosage-sensitive functions for CHD8 in p53 pathway repression, neurodevelopmental gene expression and neural progenitor fate in the embryonic neocortex. We conclude that brain development is acutely sensitive to reduced CHD8 expression and that the varying sensitivities of different progenitor populations and cellular processes to CHD8 dosage result in non-linear effects on gene transcription and brain growth. Shaun Hurley, Conor Mohan and Philipp Suetterlin have contributed equally to this work.

A TRIPARTITE CLUSTERING ANALYSIS ON MICRORNA, GENE AND DISEASE MODEL

2012 ◽  
Vol 10 (01) ◽  
pp. 1240007 ◽  
Author(s):  
CHENGCHENG SHEN ◽  
YING LIU
Keyword(s):  
Gene Expression ◽  
Clustering Algorithm ◽  
Target Genes ◽  
Regulation Of Gene Expression ◽  
Disease Model ◽  
Relational Information ◽  
Microrna Gene ◽  
Research Findings ◽  
Family Based

Alteration of gene expression in response to regulatory molecules or mutations could lead to different diseases. MicroRNAs (miRNAs) have been discovered to be involved in regulation of gene expression and a wide variety of diseases. In a tripartite biological network of human miRNAs, their predicted target genes and the diseases caused by altered expressions of these genes, valuable knowledge about the pathogenicity of miRNAs, involved genes and related disease classes can be revealed by co-clustering miRNAs, target genes and diseases simultaneously. Tripartite co-clustering can lead to more informative results than traditional co-clustering with only two kinds of members and pass the hidden relational information along the relation chain by considering multi-type members. Here we report a spectral co-clustering algorithm for k-partite graph to find clusters with heterogeneous members. We use the method to explore the potential relationships among miRNAs, genes and diseases. The clusters obtained from the algorithm have significantly higher density than randomly selected clusters, which means members in the same cluster are more likely to have common connections. Results also show that miRNAs in the same family based on the hairpin sequences tend to belong to the same cluster. We also validate the clustering results by checking the correlation of enriched gene functions and disease classes in the same cluster. Finally, widely studied miR-17-92 and its paralogs are analyzed as a case study to reveal that genes and diseases co-clustered with the miRNAs are in accordance with current research findings.

scholarly journals Identifying genetic modulators of the connectivity between transcription factors and their transcriptional targets

2016 ◽  
Vol 113 (13) ◽  
pp. E1835-E1843 ◽  
Author(s):  
Mina Fazlollahi ◽  
Ivor Muroff ◽  
Eunjee Lee ◽  
Helen C. Causton ◽  
Harmen J. Bussemaker
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Gene Regulatory Networks ◽  
Regulatory Networks ◽  
Target Genes ◽  
Regulation Of Gene Expression ◽  
Nonsynonymous Mutation ◽  
Gene Regulatory ◽  
Genetic Modulators

Regulation of gene expression by transcription factors (TFs) is highly dependent on genetic background and interactions with cofactors. Identifying specific context factors is a major challenge that requires new approaches. Here we show that exploiting natural variation is a potent strategy for probing functional interactions within gene regulatory networks. We developed an algorithm to identify genetic polymorphisms that modulate the regulatory connectivity between specific transcription factors and their target genes in vivo. As a proof of principle, we mapped connectivity quantitative trait loci (cQTLs) using parallel genotype and gene expression data for segregants from a cross between two strains of the yeast Saccharomyces cerevisiae. We identified a nonsynonymous mutation in the DIG2 gene as a cQTL for the transcription factor Ste12p and confirmed this prediction empirically. We also identified three polymorphisms in TAF13 as putative modulators of regulation by Gcn4p. Our method has potential for revealing how genetic differences among individuals influence gene regulatory networks in any organism for which gene expression and genotype data are available along with information on binding preferences for transcription factors.

scholarly journals Identification of new driver and passenger mutations within APOBEC-induced hotspot mutations in bladder cancer

2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Ming-Jun Shi ◽  
Xiang-Yu Meng ◽  
Jacqueline Fontugne ◽  
Chun-Long Chen ◽  
François Radvanyi ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bladder Cancer ◽  
Target Genes ◽  
Genetic Alterations ◽  
Driver Mutations ◽  
Joint Analysis ◽  
Tumour Suppressor Genes ◽  
Loss Of Function ◽  
Aryl Hydrocarbon ◽  
Hotspot Mutations

Abstract Background APOBEC-driven mutagenesis and functional positive selection of mutated genes may synergistically drive the higher frequency of some hotspot driver mutations compared to other mutations within the same gene, as we reported for FGFR3 S249C. Only a few APOBEC-associated driver hotspot mutations have been identified in bladder cancer (BCa). Here, we systematically looked for and characterised APOBEC-associated hotspots in BCa. Methods We analysed 602 published exome-sequenced BCas, for part of which gene expression data were also available. APOBEC-associated hotspots were identified by motif-mapping, mutation signature fitting and APOBEC-mediated mutagenesis comparison. Joint analysis of DNA hairpin stability and gene expression was performed to predict driver or passenger hotspots. Aryl hydrocarbon receptor (AhR) activity was calculated based on its target genes expression. Effects of AhR knockout/inhibition on BCa cell viability were analysed. Results We established a panel of 44 APOBEC-associated hotspot mutations in BCa, which accounted for about half of the hotspot mutations. Fourteen of them overlapped with the hotspots found in other cancer types with high APOBEC activity. They mostly occurred in the DNA lagging-strand templates and the loop of DNA hairpins. APOBEC-associated hotspots presented systematically a higher prevalence than the other mutations within each APOBEC-target gene, independently of their functional impact. A combined analysis of DNA loop stability and gene expression allowed to distinguish known passenger from known driver hotspot mutations in BCa, including loss-of-function mutations affecting tumour suppressor genes, and to predict new candidate drivers, such as AHR Q383H. We further characterised AHR Q383H as an activating driver mutation associated with high AhR activity in luminal tumours. High AhR activity was also found in tumours presenting amplifications of AHR and its co-receptor ARNT. We finally showed that BCa cells presenting those different genetic alterations were sensitive to AhR inhibition. Conclusions Our study identified novel potential drivers within APOBEC-associated hotspot mutations in BCa reinforcing the importance of APOBEC mutagenesis in BCa. It could allow a better understanding of BCa biology and aetiology and have clinical implications such as AhR as a potential therapeutic target. Our results also challenge the dogma that all hotspot mutations are drivers and mostly gain-of-function mutations affecting oncogenes.

scholarly journals A Retinoid-Resistant Acute Promyelocytic Leukemia Subclone Expresses a Dominant Negative PML-RARα Mutation

Blood ◽  
1997 ◽  
Vol 89 (12) ◽  
pp. 4282-4289 ◽  
Author(s):  
Wenlin Shao ◽  
Laura Benedetti ◽  
William W. Lamph ◽  
Clara Nervi ◽  
Wilson H. Miller
Keyword(s):  
Gene Expression ◽  
Retinoic Acid ◽  
Ligand Binding ◽  
Cell Line ◽  
Acute Promyelocytic Leukemia ◽  
Regulation Of Gene Expression ◽  
Promyelocytic Leukemia ◽  
Dominant Negative

Abstract The unique t(15; 17) of acute promyelocytic leukemia (APL) fuses the PML gene with the retinoic acid receptor α (RARα) gene. Although retinoic acid (RA) inhibits cell growth and induces differentiation in human APL cells, resistance to RA develops both in vitro and in patients. We have developed RA-resistant subclones of the human APL cell line, NB4, whose nuclear extracts display altered RA binding. In the RA-resistant subclone, R4, we find an absence of ligand binding of PML-RARα associated with a point mutation changing a leucine to proline in the ligand-binding domain of the fusion PML-RARα protein. In contrast to mutations in RARα found in retinoid-resistant HL60 cells, in this NB4 subclone, the coexpressed RARα remains wild-type. In vitro expression of a cloned PML-RARα with the observed mutation in R4 confirms that this amino acid change causes the loss of ligand binding, but the mutant PML-RARα protein retains the ability to heterodimerize with RXRα and thus to bind to retinoid response elements (RAREs). This leads to a dominant negative block of transcription from RAREs that is dose-dependent and not relieved by RA. An unrearranged RARα engineered with this mutation also lost ligand binding and inhibited transcription in a dominant negative manner. We then found that the mutant PML-RARα selectively alters regulation of gene expression in the R4 cell line. R4 cells have lost retinoid-regulation of RXRα and RARβ and the RA-induced loss of PML-RARα protein seen in NB4 cells, but retain retinoid-induction of CD18 and CD38. Thus, the R4 cell line provides data supporting the presence of an RARα-mediated pathway that is independent from gene expression induced or repressed by PML-RARα. The high level of retinoid resistance in vitro and in vivo of cells from some relapsed APL patients suggests similar molecular changes may occur clinically.

scholarly journals Nrf Transcription Factors in Keratinocytes Are Essential for Skin Tumor Prevention but Not for Wound Healing

2006 ◽  
Vol 26 (10) ◽  
pp. 3773-3784 ◽  
Author(s):  
Ulrich auf dem Keller ◽  
Marcel Huber ◽  
Tobias A. Beyer ◽  
Angelika Kümin ◽  
Christina Siemes ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transgenic Mice ◽  
Wound Repair ◽  
Target Genes ◽  
Dominant Negative ◽  
Skin Tumor ◽  
Cellular Stress Response ◽  
Skin Development

ABSTRACT The Nrf2 transcription factor is a key player in the cellular stress response through its regulation of cytoprotective genes. In this study we determined the role of Nrf2-mediated gene expression in keratinocytes for skin development, wound repair, and skin carcinogenesis. To overcome compensation by the related Nrf1 and Nrf3 proteins, we expressed a dominant-negative Nrf2 mutant (dnNrf2) in the epidermis of transgenic mice. The functionality of the transgene product was verified in vivo using mice doubly transgenic for dnNrf2 and an Nrf2-responsive reporter gene. Surprisingly, no abnormalities of the epidermis were observed in dnNrf2-transgenic mice, and even full-thickness skin wounds healed normally. However, the onset, incidence, and multiplicity of chemically induced skin papillomas were strikingly enhanced, whereas the progression to squamous cell carcinomas was unaltered. We provide evidence that the enhanced tumorigenesis results from reduced basal expression of cytoprotective Nrf target genes, leading to accumulation of oxidative damage and reduced carcinogen detoxification. Our results reveal a crucial role of Nrf-mediated gene expression in keratinocytes in the prevention of skin tumors and suggest that activation of Nrf2 in keratinocytes is a promising strategy to prevent carcinogenesis of this highly exposed organ.

The dominant negative thyroid hormone receptor β-mutant Δ337T alters PPARα signaling in heart

2007 ◽  
Vol 292 (2) ◽  
pp. E453-E460 ◽  
Author(s):  
Norman E. Buroker ◽  
Martin E. Young ◽  
Caimiao Wei ◽  
Kyle Serikawa ◽  
Ming Ge ◽  
...  
Keyword(s):  
Gene Expression ◽  
Thyroid Hormone ◽  
Protein Content ◽  
Nuclear Receptors ◽  
Cross Talk ◽  
Target Genes ◽  
Thyroid Hormone Receptor ◽  
Dominant Negative ◽  
Variable Cross ◽  
Multiple Genes

PPARα and TR independently regulate cardiac metabolism. Although ligands for both these receptors are currently under evaluation for treatment of congestive heart failure, their interactions or signaling cooperation have not been investigated in heart. We tested the hypothesis that cardiac TRs interact with PPARα regulation of target genes and used mice exhibiting a cardioselective Δ337T TRβ1 mutation (MUT) to reveal cross-talk between these nuclear receptors. This dominant negative transgene potently inhibits DNA binding for both wild-type (WT) TRα and TRβ. We used UCP3 and MTE-1 as principal reporters and analyzed gene expression from hearts of transgenic (MUT) and nontransgenic (WT) littermates 6 h after receiving either specific PPARα ligand (WY-14643) or vehicle. Interactions were determined through qRT-PCR analyses, and the extent of these interactions across multiple genes was determined using expression arrays. In the basal state, we detected no differences between groups for protein content for UCP3, PPARα, TRα2, RXRβ, or PGC-1α. However, protein content for TRα1 and the PPARα heterodimeric partner RXRα was diminished in MUT, whereas PPARβ increased. We demonstrated cross-talk between PPAR and TR for multiple genes, including the reporters UCP3 and MTE1. WY-14643 induced a twofold increase in UCP3 gene expression that was totally abrogated in MUT. We demonstrated variable cross-talk patterns, indicating that multiple mechanisms operate according to individual target genes. The non-ligand-binding TRβ1 mutation alters expression for multiple nuclear receptors, providing a novel mechanism for interaction that has not been previously demonstrated. These results indicate that therapeutic response to PPARα ligands may be determined by thyroid hormone state and TR function.

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