Heat shock factor 2 is a stress‐responsive mediator of neuronal migration defects in models of fetal alcohol syndrome

Fetal alcohol spectrum disorder (FASD) is a frequent cause of mental retardation. However, the molecular mechanisms underlying brain development defects induced by maternal alcohol consumption during pregnancy are unclear. We used normal andHsf2‐deficient mice and cell systems to uncover a pivotal role for heat shock factor 2 (HSF2) in radial neuronal migration defects in the cortex, a hallmark of fetal alcohol exposure. Upon fetal alcohol exposure, HSF2 is essential for the triggering of HSF1 activation, which is accompanied by distinctive post‐translational modifications, and HSF2 steers the formation of atypical alcohol‐specific HSF1–HSF2 heterocomplexes. This perturbs the in vivo binding of HSF2 to heat shock elements (HSEs) in genes that control neuronal migration in normal conditions, such as p35 or the MAPs(microtubule‐associated proteins, such as Dclk1 and Dcx), and alters their expression. In the absence of HSF2, migration defects as well as alterations in gene expression are reduced. Thus, HSF2, as a sensor for alcohol stress in the fetal brain, acts as a mediator of the neuronal migration defects associated with FASD

Epigenetic priming of immune/inflammatory pathways activation and abnormal activity of cell cycle pathway in a perinatal model of white matter injury

Prenatal inflammatory insults accompany prematurity and provoke diffuse white matter injury (DWMI), which is associated with increased risk of neurodevelopmental pathologies, including autism spectrum disorders. DWMI results from maturation arrest of oligodendrocyte precursor cells (OPCs), a process that is poorly understood. Here, by using a validated mouse model of OPC maturation blockade, we provide the genome-wide ID card of the effects of neuroinflammation on OPCs that reveals the architecture of global cell fate issues underlining their maturation blockade. First, we find that, in OPCs, neuroinflammation takes advantage of a primed epigenomic landscape and induces abnormal overexpression of genes of the immune/inflammatory pathways: these genes strikingly exhibit accessible chromatin conformation in uninflamed OPCs, which correlates with their developmental, stage-dependent expression, along their normal maturation trajectory, as well as their abnormal upregulation upon neuroinflammation. Consistently, we observe the positioning on DNA of key transcription factors of the immune/inflammatory pathways (IRFs, NFkB), in both unstressed and inflamed OPCs. Second, we show that, in addition to the general perturbation of the myelination program, neuroinflammation counteracts the physiological downregulation of the cell cycle pathway in maturing OPCs. Neuroinflammation therefore perturbs cell identity in maturing OPCs, in a global manner. Moreover, based on our unraveling of the activity of genes of the immune/inflammatory pathways in prenatal uninflamed OPCs, the mere suppression of these proinflammatory mediators, as currently proposed in the field, may not be considered as a valid neurotherapeutic strategy

CBP-HSF2 structural and functional interplay in Rubinstein-Taybi neurodevelopmental disorder

Rubinstein-Taybi syndrome (RSTS) is a neurodevelopmental disorder with unclear underlying mechanisms. Here, the authors unravel the contribution of a stress-responsive pathway to RSTS where impaired HSF2 acetylation, due to RSTS-associated CBP/EP300 mutations, alters the expression of neurodevelopmental players, in keeping with hallmarks of cell-cell adhesion defects.Patients carrying autosomal dominant mutations in the histone/lysine acetyl transferases CBP or EP300 develop a neurodevelopmental disorder: Rubinstein-Taybi syndrome (RSTS). The biological pathways underlying these neurodevelopmental defects remain elusive. Here, we unravel the contribution of a stress-responsive pathway to RSTS. We characterize the structural and functional interaction between CBP/EP300 and heat-shock factor 2 (HSF2), a tuner of brain cortical development and major player in prenatal stress responses in the neocortex: CBP/EP300 acetylates HSF2, leading to the stabilization of the HSF2 protein. Consequently, RSTS patient-derived primary cells show decreased levels of HSF2 and HSF2-dependent alteration in their repertoire of molecular chaperones and stress response. Moreover, we unravel a CBP/EP300-HSF2-N-cadherin cascade that is also active in neurodevelopmental contexts, and show that its deregulation disturbs neuroepithelial integrity in 2D and 3D organoid models of cerebral development, generated from RSTS patient-derived iPSC cells, providing a molecular reading key for this complex pathology.</p

HSFs, Stress Sensors and Sculptors of Transcription Compartments and Epigenetic Landscapes

International audienceStarting as a paradigm for stress responses, the study of the transcription factor (TF) family of heat shock factors (HSFs) has quickly and widely expanded these last decades, thanks to their fascinating and significant involvement in a variety of pathophysiological processes, including development, reproduction, neurodegeneration and carcinogenesis. HSFs, originally defined as classical TFs, strikingly appeared to play a central and often pioneering role in reshaping the epigenetic landscape. In this review, we describe how HSFs are able to sense the epigenetic environment, and we review recent data that support their role as sculptors of the chromatin landscape through their complex interplay with chromatin remodelers, histone-modifying enzymes and non-coding RNAs

A novel Nodal enhancer dependent on pluripotency factors and Smad2/3 signaling conditions a regulatory switch during epiblast maturation

During early development, modulations in the expression of Nodal, a TGFβ family member, determine the specification of embryonic and extra-embryonic cell identities. Nodal has been extensively studied in the mouse, but aspects of its early expression remain unaccounted for. We identified a conserved hotspot for the binding of pluripotency factors at the Nodal locus and called this sequence “highly bound element” (HBE). Luciferase-based assays, the analysis of fluorescent HBE reporter transgenes, and a conditional mutation of HBE allowed us to establish that HBE behaves as an enhancer, is activated ahead of other Nodal enhancers in the epiblast, and is essential to Nodal expression in embryonic stem cells (ESCs) and in the mouse embryo. We also showed that HBE enhancer activity is critically dependent on its interaction with the pluripotency factor Oct4 and on Activin/Nodal signaling. Use of an in vitro model of epiblast maturation, relying on the differentiation of ESCs into epiblast stem cells (EpiSCs), revealed that this process entails a shift in the regulation of Nodal expression from an HBE-driven phase to an ASE-driven phase, ASE being another autoregulatory Nodal enhancer. Deletion of HBE in ESCs or in EpiSCs allowed us to show that HBE, although not necessary for Nodal expression in EpiSCs, is required in differentiating ESCs to activate the differentiation-promoting ASE and therefore controls this regulatory shift. Our findings clarify how early Nodal expression is regulated and suggest how this regulation can promote the specification of extra-embryonic precusors without inducing premature differentiation of epiblast cells. More generally, they open new perspectives on how pluripotency factors achieve their function

Alcohol exposure promotes DNA methyltransferase DNMT3A upregulation through reactive oxygen species-dependent mechanisms

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Heat Shock Factor 2 Protects against Proteotoxicity by Maintaining Cell-Cell Adhesion

International audienceMaintenance of protein homeostasis, through inducible expression of molecular chaperones, is essential for cell survival under protein-damaging conditions. The expression and DNA-binding activity of heat shock factor 2 (HSF2), a member of the heat shock transcription factor family, increase upon exposure to prolonged proteotoxicity. Nevertheless, the specific roles of HSF2 and the global HSF2-dependent gene expression profile during sustained stress have remained unknown. Here, we found that HSF2 is critical for cell survival during prolonged proteotoxicity. Strikingly, our RNA sequencing (RNA-seq) analyses revealed that impaired viability of HSF2-deficient cells is not caused by inadequate induction of molecular chaperones but is due to marked downregulation of cadherin superfamily genes. We demonstrate that HSF2-dependent maintenance of cadherin-mediated cell-cell adhesion is required for protection against stress induced by proteasome inhibition. This study identifies HSF2 as a key regulator of cadherin superfamily genes and defines cell-cell adhesion as a determinant of proteotoxic stress resistance

HBE is an enhancer active in pluripotent cells.

<p>(A) HBE is a hotspot for the binding of pluripotency factors and Smad3. <i>Nodal</i> regulatory elements are represented by green boxes and <i>Nodal</i> exons by blue boxes. Binding peaks of Nanog, Sox2, Klf4, Oct4, and Smad3 at the <i>Nodal</i> locus in ESCs are represented by black bars that represent either the summit of the peak of ChIP-seq data or its center for ChIP-chip data aligned to UCSC Genome Browser on Mouse Feb. 2006 (NCBI36/mm8) Assembly (<a href="http://genome.ucsc.edu/" target="_blank">http://genome.ucsc.edu/</a>). (B and C) Luciferase reporter assays for early <i>Nodal</i> enhancers using either a minimal (E1b) or the endogenous promoter (NIS), in ESCs (B), or in EpiSCs (C). Luciferase activities are shown relative to HBE construct. An asterisk indicates significant differences from the control (ctrl) (<i>p</i><0.01).</p

HBE is required for activation of <i>Nodal</i> in the early mouse embryo.

<p>Detection of mCherry (A, B, C, and D) and YFP (A′, B′, C′, and D′) in E4.5 (A–B″) or E6.5 (C–D″) aggregation chimeras generated from <i>Nodal^condHBE-YFP</i> (A–A″ and C–C″) or <i>Nodal^ΔHBE-YFP</i> (B–B″ and D–D″) ES cells and WT embryos. Images are single confocal sections. Cortical actin in blue. <i>n</i> is the number of representative embryos on the total number of embryos analyzed. Scale bar, 25 µm for E4.5 embryos and 50 µm for E6.5 embryos.</p

HBE is required for <i>Nodal</i> expression in ESCs but not in EpiSCs.

<p>(A) Depiction of the two <i>Nodal</i> alleles (WT on top and recombinant at the bottom) before and after Cre recombination. (B–C″) Expression of Oct4 (B, C) and YFP (B′, C′) in recombinant ESCs before (B–B″) and after (C–C″) Cre recombination. (D–E″) Expression of Oct4 (D, E) and YFP (D′, E′) in recombinant EpiSCs, 6 d after transfection with a control plasmid (D–D″) or with Cre recombinase (E–E″). Single confocal sections. <i>n</i> is the number of YFP-positive colonies. Scale bar, 25 µm.</p