15 research outputs found

    From enhanceropathies to the epigenetic manifold underlying human cognition

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    A vast portion of intellectual disability and autism spectrum disorders is genetically caused by mutations in chromatin modulators. These proteins play key roles in development and are also highly expressed in the adult brain. Specifically, the pivotal role of chromatin regulation in transcription has placed enhancers at the core of neurodevelopmental disorders (NDDs) studies, ushering in the coining of the term enhanceropathies. The convergence of these disorders is multilayered, spanning from molecular causes to pathophysiological traits, including extensive overlaps between enhanceropathies and neurocristopathies. The reconstruction of epigenetic circuitries wiring development and underlying cognitive functions has gone hand in hand with the development of tools that increase the sensitivity of identifying regulatory regions and linking enhancers to their target genes. The available models, including loop extrusion and phase separation, have been bringing into relief complementary aspects to interpret gene regulation datasets, reinforcing the idea that enhancers are not all the same and that regulatory regions possess shades of enhancer-ness and promoter-ness. The current limits in enhancer definition, within the emerging broader understanding of chromatin dynamics in time and space, are now on the verge of being transformed by the possibility to interrogate developmentally relevant three-dimensional cellular models at single-cell resolution. Here we discuss the contours of how these technological advances, as well as the epistemic limitations they are set to overcome, may well usher in a change of paradigm for NDDs, moving the quest for convergence from enhancers to the four-dimensional (4D) genome

    Dosage analysis of the 7q11.23 Williams region identifies BAZ1B as a major human gene patterning the modern human face and underlying self-domestication

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    We undertook a functional dissection of chromatin remodeler BAZ1B in neural crest (NC) stem cells (NCSCs) from a uniquely informative cohort of typical and atypical patients harboring 7q11.23 copy number variants. Our results reveal a key contribution of BAZ1B to NCSC in vitro induction and migration, coupled with a crucial involvement in NC-specific transcriptional circuits and distal regulation. By intersecting our experimental data with new paleogenetic analyses comparing modern and archaic humans, we found a modern-specific enrichment for regulatory changes both in BAZ1B and its experimentally defined downstream targets, thereby providing the first empirical validation of the human self-domestication hypothesis and positioning BAZ1B as a master regulator of the modern human face. In so doing, we provide experimental evidence that the craniofacial and cognitive/behavioral phenotypes caused by alterations of the Williams-Beuren syndrome critical region can serve as a powerful entry point into the evolution of the modern human face and prosociality

    YY1 haploinsufficiency causes an intellectual disability syndrome featuring transcriptional and chromatin dysfunction

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    Yin and yang 1 (YY1) is a well-known zinc-finger transcription factor with crucial roles in normal development and malignancy. YY1 acts both as a repressor and as an activator of gene expression. We have identified 23 individuals with de novo mutations or deletions of YY1 and phenotypic features that define a syndrome of cognitive impairment, behavioral alterations, intrauterine growth restriction, feeding problems, and various congenital malformations. Our combined clinical and molecular data define "YY1 syndrome" as a haploinsufficiency syndrome. Through immunoprecipitation of YY1-bound chromatin from affected individuals' cells with antibodies recognizing both ends of the protein, we show that YY1 deletions and missense mutations lead to a global loss of YY1 binding with a preferential retention at high-occupancy sites. Finally, we uncover a widespread loss of H3K27 acetylation in particular on the YY1-bound enhancers, underscoring a crucial role for YY1 in enhancer regulation. Collectively, these results define a clinical syndrome caused by haploinsufficiency of YY1 through dysregulation of key transcriptional regulators.Michele Gabriele, Anneke T. Vulto-van Silfhout, Pierre-Luc Germain, Alessandro Vitriolo, Raman Kumar, Evelyn Douglas, Eric Haan, Kenjiro Kosaki, Toshiki Takenouchi, Anita Rauch, Katharina Steindl, Eirik Frengen, Doriana Misceo, Christeen Ramane J. Pedurupillay, Petter Stromme, Jill A. Rosenfeld, Yunru Shao, William J. Craigen, Christian P. Schaaf, David Rodriguez-Buritica, Laura Farach, Jennifer Friedman, Perla Thulin, Scott D. McLean, Kimberly M. Nugent, Jenny Morton, Jillian Nicholl, Joris Andrieux, Asbjørg Stray-Pedersen, Pascal Chambon, Sophie Patrier, Sally A. Lynch, Susanne Kjaergaard, Pernille M. Tørring, Charlotte Brasch-Andersen, Anne Ronan, Arie van Haeringen, Peter J. Anderson, Zöe Powis, Han G. Brunner, Rolph Pfundt, Janneke H.M. Schuurs-Hoeijmakers, Bregje W.M. van Bon, Stefan Lelieveld, Christian Gilissen, Willy M. Nillesen, Lisenka E.L.M. Vissers, Jozef Gecz, David A. Koolen, Giuseppe Testa, Bert B.A. de Vrie

    The guanine nucleotide exchange factor Arhgef7/beta Pix promotes axon formation upstream of TC10

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    The characteristic six layers of the mammalian neocortex develop sequentially as neurons are generated by neural progenitors and subsequently migrate past older neurons to their final position in the cortical plate. One of the earliest steps of neuronal differentiation is the formation of an axon. Small GTPases play essential roles during this process by regulating cytoskeletal dynamics and intracellular trafficking. While the function of GTPases has been studied extensively in cultured neurons and in vivo much less is known about their upstream regulators. Here we show that Arhgef7 (also called \u3b2Pix or Cool1) is essential for axon formation during cortical development. The loss of Arhgef7 results in an extensive loss of axons in cultured neurons and in the developing cortex. Arhgef7 is a guanine-nucleotide exchange factor (GEF) for Cdc42, a GTPase that has a central role in directing the formation of axons during brain development. However, active Cdc42 was not able to rescue the knockdown of Arhgef7. We show that Arhgef7 interacts with the GTPase TC10 that is closely related to Cdc42. Expression of active TC10 can restore the ability to extend axons in Arhgef7-deficient neurons. Our results identify an essential role of Arhgef7 during neuronal development that promotes axon formation upstream of TC10

    DNA Methylation Signature for EZH2 Functionally Classifies Sequence Variants in Three PRC2 Complex Genes.

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    Weaver syndrome (WS), an overgrowth/intellectual disability syndrome (OGID), is caused by pathogenic variants in the histone methyltransferase EZH2, which encodes a core component of the Polycomb repressive complex-2 (PRC2). Using genome-wide DNA methylation (DNAm) data for 187 individuals with OGID and 969 control subjects, we show that pathogenic variants in EZH2 generate a highly specific and sensitive DNAm signature reflecting the phenotype of WS. This signature can be used to distinguish loss-of-function from gain-of-function missense variants and to detect somatic mosaicism. We also show that the signature can accurately classify sequence variants in EED and SUZ12, which encode two other core components of PRC2, and predict the presence of pathogenic variants in undiagnosed individuals with OGID. The discovery of a functionally relevant signature with utility for diagnostic classification of sequence variants in EZH2, EED, and SUZ12 supports the emerging paradigm shift for implementation of DNAm signatures into diagnostics and translational research

    MULTI-OMIC DECONVOLUTION OF THE REGULATORY NETWORKS UNDERLYING NEURODEVELOPMENTAL AND AUTISM SPECTRUM DISORDERS: A MULTIDIMENTIONAL ANALYSIS FOR A NEW DISEASE MODELLING PARADIGM

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    Recent literature has highlighted that mutations causing neurodevelopmental syndromes are particularly enriched in genes related to chromatin regulation and synaptic functions. While the latter could be easily predicted, the former shed seeds to the flourishing of epigenomic studies focused on this type of disorders. Intriguingly, most of such disorders couple different shades of intellectual disabilities with peculiar cranio-facial features and systemic defects which are shared, opposite or unique across them. I have set up a dynamic framework of analysis, that encompasses the comparison of multiple disorders, cell types and cultures, to highlight cell-type specific and developmentally-relevant paths of transcriptional deregulation. Building on my lab\u2019s expertise to harness potency and stability of induced pluripotent stem cells (iPSCs), I identified two main axes of development through which we could characterize on the one hand cerebral cortex related dysregulations and on the other hand cranio-facial features associated traits, peripheral nervous system- and cardiovascular system-related dysregulations. The former is based on the production of adult glutamatergic cortical neurons through ectopic expression of NGN2 in iPSCs and, in parallel, through production of brain organoids: 3D cultures obtained by neuronal differentiation and patterning via sequential exposure to small molecules. The latter is based on differentiation of iPSCs to neural crest stem cells (NCSCs) and mesenchymal stem cells (MSCs). I collected and standardised transcriptomic data coming from controls- and patient-derived iPSCs accounting for six disorders, NCSCs for five disorders and MSCs for two disorders; NGN2 neurons for two disorders and brain organoid for one disorder. During my research I helped define new standards for RNA-seq experiments tailored for differential-expression analysis and developed or implemented tools to make cross-disorder and cross-tissue comparisons in a connectable way. This work let me identify regulatory circuitries shared by all disorders or by subgroups characterized by shared phenotypes; symmetric deregulations in disorders caused by mutation of opposite histone modifiers; unexpected subgroups that will require further investigation. For most disorders, my work confirms previously published evidence that dysregulations identified at the pluripotent stage can be inherited and amplified in disease-relevant tissues in a tissue-specific fashion. Thus, I was capable of identifying disease-specific dysregulations at the pluripotent stage and in disease-relevant tissues; I drew conclusions on iPSCs cross-disorder transcriptional dysregulations through the definition of transcriptional modules; I implemented an analytical framework to boost the ability of identifying the effect of knocking down a certain gene on transcriptional and epigenetic landscapes; I identified sets of genes whose deregulation at the pluripotent stage reverberates and amplifies along development, funnelling and filtering several analyses to converge on a small set of actionable targets; I identified a small set of potential direct targets of PRC2 complex involved in brain development and on the onset of Weaver Syndrome; I identified BAZ1B-specific transcriptional dysregulations in NCSCs that confirm its importance for migration and craniofacial morphogenesis but more in general for chromatin remodelling and human evolution; I helped in the molecular characterization of YY1 mutations, which led to the identification of Gabriele-de Vries Syndrome; I contributed to the molecular characterization of Kabuki Syndrome in neural crest and adult cortical neurons

    SPILLO-PBSS : detecting hidden binding sites within protein 3D-structures through a flexible structure-based approach

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    The study reports a flexible structure-based approach aimed at identifying binding sites within target proteins starting from a well-defined reference binding site. The method, named SPILLO potential binding sites searcher (SPILLO-PBSS), includes a suitably designed tolerance which allows an efficient recognition of the potential binding sites regardless of both involved residues and protein conformation. Hence, the proposed method overcomes the rigidity which affects the available approaches and which prevents a proper analysis of distorted binding sites. We apply SPILLO-PBSS to several test cases, including the search for the guanosine diphosphate binding site in distorted H-Ras proteins and the identification of acetylcholine binding proteins from among a library of heterogeneous resolved proteins. Tests are also performed to compare SPILLO-PBSS with other related and available methods. The encouraging results confirm the notable potentialities of this approach and lay the foundation for its use to analyze and predict target proteins on a proteome-wide scale

    Dosage analysis of the 7q11.23 Williams region identifies BAZ1B as a major human gene patterning the modern human face and underlying self-domestication

    No full text
    We undertook a functional dissection of chromatin remodeler BAZ1B in neural crest (NC) stem cells (NCSCs) from a uniquely informative cohort of typical and atypical patients harboring 7q11.23 copy number variants. Our results reveal a key contribution of BAZ1B to NCSC in vitro induction and migration, coupled with a crucial involvement in NC-specific transcriptional circuits and distal regulation. By intersecting our experimental data with new paleogenetic analyses comparing modern and archaic humans, we found a modern-specific enrichment for regulatory changes both in BAZ1B and its experimentally defined downstream targets, thereby providing the first empirical validation of the human self-domestication hypothesis and positioning BAZ1B as a master regulator of the modern human face. In so doing, we provide experimental evidence that the craniofacial and cognitive/behavioral phenotypes caused by alterations of the Williams-Beuren syndrome critical region can serve as a powerful entry point into the evolution of the modern human face and prosociality

    The guanine nucleotide exchange factor Arhgef7/βPix promotes axon formation upstream of TC10

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    The characteristic six layers of the mammalian neocortex develop sequentially as neurons are generated by neural progenitors and subsequently migrate past older neurons to their final position in the cortical plate. One of the earliest steps of neuronal differentiation is the formation of an axon. Small GTPases play essential roles during this process by regulating cytoskeletal dynamics and intracellular trafficking. While the function of GTPases has been studied extensively in cultured neurons and in vivo much less is known about their upstream regulators. Here we show that Arhgef7 (also called βPix or Cool1) is essential for axon formation during cortical development. The loss of Arhgef7 results in an extensive loss of axons in cultured neurons and in the developing cortex. Arhgef7 is a guanine-nucleotide exchange factor (GEF) for Cdc42, a GTPase that has a central role in directing the formation of axons during brain development. However, active Cdc42 was not able to rescue the knockdown of Arhgef7. We show that Arhgef7 interacts with the GTPase TC10 that is closely related to Cdc42. Expression of active TC10 can restore the ability to extend axons in Arhgef7-deficient neurons. Our results identify an essential role of Arhgef7 during neuronal development that promotes axon formation upstream of TC10
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