Project description:Heterozygous loss-of function mutations in CHD7 (chromodomain helicase DNA-binding protein 7) lead to CHARGE syndrome, a complex developmental disorder affecting craniofacial structures, peripheral nerves and several organ systems like eyes, ears, nose and heart. Recently, it was demonstrated that CHD7 is essential for the formation of multipotent migratory neural crest cells, which migrate from the neural tube to many regions of the embryo, where they differentiate into various tissues including craniofacial and heart structures. So far only few CHD7 target genes involved in neural crest cell development have been identified and the role of CHD7 in neural crest cell guidance and the regulation of mesenchymal-epithelial transition is unknown. Therefore, we undertook a genome-wide microarray expression analysis on wild-type and CHD7 deficient (Chd7Whi/+ and Chd7Whi/Whi) mouse embryos at day 9.5, the time point of neural crest cell migration. We identified 98 genes showing greater than two fold differences in expression (log2 fold-change) and a P-value to false discovery rate (FDR) < 0.05 between wild-type and Chd7Whi/Whi embryos. Interestingly, many misregulated genes are involved in neural crest cell and axon guidance like semaphorins and ephrin receptors. By performing knockdown experiments for Chd7 and one of its target genes, namely semaphorin3a in Xenopus laevis embryos, we could show abnormalities in the migration of neural crest cells in vivo. Additionally, we detected non-synonymous SEMA3A variations in 3 out of 45 CHD7 negative CHARGE patients suggesting a role for SEMA3A in the pathogenesis of CHARGE syndrome. To identify genes that are affected by the absence of functional Chd7 at the time point of neural crest cell migration, the expression profiles of E9.5 wild-type, Chd7Whi/+ and Chd7Whi/Whi female mouse embryos were compared by whole-genome microarray analysis. Mouse embryos of the same sex were used to avoid sex-dependent gene expression effects. We performed microarray analysis by using the Agilent-026655 Whole Mouse Genome Microarray 4x44K v2 (Agilent) on four biological replicates from each group.
Project description:Heterozygous loss-of function mutations in CHD7 (chromodomain helicase DNA-binding protein 7) lead to CHARGE syndrome, a complex developmental disorder affecting craniofacial structures, peripheral nerves and several organ systems like eyes, ears, nose and heart. Recently, it was demonstrated that CHD7 is essential for the formation of multipotent migratory neural crest cells, which migrate from the neural tube to many regions of the embryo, where they differentiate into various tissues including craniofacial and heart structures. So far only few CHD7 target genes involved in neural crest cell development have been identified and the role of CHD7 in neural crest cell guidance and the regulation of mesenchymal-epithelial transition is unknown. Therefore, we undertook a genome-wide microarray expression analysis on wild-type and CHD7 deficient (Chd7Whi/+ and Chd7Whi/Whi) mouse embryos at day 9.5, the time point of neural crest cell migration. We identified 98 genes showing greater than two fold differences in expression (log2 fold-change) and a P-value to false discovery rate (FDR) < 0.05 between wild-type and Chd7Whi/Whi embryos. Interestingly, many misregulated genes are involved in neural crest cell and axon guidance like semaphorins and ephrin receptors. By performing knockdown experiments for Chd7 and one of its target genes, namely semaphorin3a in Xenopus laevis embryos, we could show abnormalities in the migration of neural crest cells in vivo. Additionally, we detected non-synonymous SEMA3A variations in 3 out of 45 CHD7 negative CHARGE patients suggesting a role for SEMA3A in the pathogenesis of CHARGE syndrome.
Project description:Neurocristopathies such as CHARGE syndrome result from aberrant neural crest development. A large proportion of CHARGE cases are attributed to pathogenic variants in the gene encoding CHD7, chromodomain helicase DNA binding protein 7, which remodels chromatin. While the role for CHD7 in neural crest development is well documented, how this factor is specifically upregulated in neural crest cells is not understood. Here, we use epigenomic profiling of chick and human neural crest to identify a cohort of enhancers regulating Chd7 expression in neural crest cells and other tissues. We functionally validate upstream transcription factor binding at candidate enhancers, revealing novel epistatic relationships between neural crest master regulators and Chd7, showing tissue-specific regulation of a globally-acting chromatin remodeller for the first time. Furthermore, we find conserved enhancer features in human embryonic epigenomic data and validate the activity of the human equivalent CHD7 enhancers in the chick embryo. Our findings embed Chd7 in the neural crest gene regulatory network and offer potentially clinically relevant elements for interpreting CHARGE syndrome cases without causative allocation.
Project description:Neurocristopathies such as CHARGE syndrome result from aberrant neural crest development. A large proportion of CHARGE cases are attributed topathogenic variantsin the gene encoding CHD7, chromodomain helicase DNA binding protein 7, which remodels chromatin. While the role for CHD743in neural crest development is well documented,how this factor is specifically upregulated in neural crest cells is not understood. Here, we use epigenomic profiling of chick and human neural crest to identify a cohort of enhancers regulating Chd7 expression in neural crest cells and other tissues. We functionally validate upstream transcription factor binding at candidate enhancers, revealing novel epistatic relationships between neural crest master regulators and Chd7, showing tissue-specific regulation of a globally-acting chromatin remodeller for the first time. Furthermore, we find conserved enhancer features in human embryonic epigenomic data and validate the activity of the human equivalent CHD7 enhancers in the chick embryo. Our findings embed Chd7 in the neural crest gene regulatory network and offer potentially clinically relevant elements for interpreting CHARGE syndrome cases without causative allocation.
Project description:Neurocristopathies such as CHARGE syndrome result from aberrant neural crest development. A large proportion of CHARGE cases are attributed topathogenic variantsin the gene encoding CHD7, chromodomain helicase DNA binding protein 7, which remodels chromatin. While the role for CHD743in neural crest development is well documented,how this factor is specifically upregulated in neural crest cells is not understood. Here, we use epigenomic profiling of chick and human neural crest to identify a cohort of enhancers regulating Chd7 expression in neural crest cells and other tissues. We functionally validate upstream transcription factor binding at candidate enhancers, revealing novel epistatic relationships between neural crest master regulators and Chd7, showing tissue-specific regulation of a globally-acting chromatin remodeller for the first time. Furthermore, we find conserved enhancer features in human embryonic epigenomic data and validate the activity of the human equivalent CHD7 enhancers in the chick embryo. Our findings embed Chd7 in the neural crest gene regulatory network and offer potentially clinically relevant elements for interpreting CHARGE syndrome cases without causative allocation.
Project description:CHARGE syndrome is caused by heterozygous mutations in a chromatin remodeler CHD7 and characterized by a set of malformations historically postulated to arise from defects in the neural crest formation during embryogenesis. To better delineate neural crest defects in CHARGE syndrome, we generated induced pluripotent stem cells (iPSCs) from two patients with typical syndrome manifestations, and characterized neural crest cells differentiated in vitro from these iPSCs (iPSC-NCCs). We found that expression of genes associated with cell migration was altered in CHARGE iPSC-NCCs as compared to control iPSC-NCCs. Consistently, CHARGE iPSC-NCCs showed defective delamination, migration and motility in vitro, and their transplantation in ovo revealed overall defective migratory activity in the chick embryo. Altogether, our results support the historical inference that CHARGE syndrome patients have defects in neural crest migration and provide the first successful application of patient-derived iPSCs in modeling craniofacial disorders.
Project description:Neural crest cells are multipotent cells that delaminate from the neuroepithelium, migrating throughout the embryo. Aberrant migration causes developmental defects. Animal models are improving our understanding of neural crest anomalies, but in vivo migration behaviours are poorly understood. Here, we demonstrate that murine neural crest cells display actin-based lamellipodia and filopodia in vivo. Using neural crest-specific knockouts or inhibitors, we show that the serine-threonine kinase Glycogen Synthase Kinase-3 (GSK3), and the cytoskeletal regulator Lamellipodin (Lpd), are required for lamellipodia formation whilst preventing focal adhesion maturation. Lpd is a novel substrate of GSK3 and phosphorylation of Lpd favours interactions with the Scar/WAVE complex (lamellipodia formation) at the expense of VASP and Mena interactions (adhesion maturation and filopodia formation). This improved understanding of cytoskeletal regulation in mammalian neural crest migration has general implications for neural crest anomalies and cancer.
Project description:Neural crest cells are migratory progenitor cells that contribute to nearly all tissues and organs throughout the body. Their formation, migration and differentiation are regulated by a multitude of signaling pathways, that when disrupted can lead to disorders termed neurocristopathies. While work in avian and amphibian species has revealed essential factors governing the specification and induction of neural crest cells during gastrulation and neurulation in non-mammalian species, their functions do not appear to be conserved in mice, leaving major gaps in our understanding of neural crest cell formation in mammals. Here we describe Germ Cell Nuclear Factor (GCNF/Nr6a1), an orphan nuclear receptor, as a critical regulator of neural crest cell formation in mice. Gcnf null mutant mice, exhibit a major disruption of neural crest cell formation. The purpose of this experiment is to examine gene expression changes in response to Gcnf mutation in E9.0 mouse embryos.
Project description:Neural crest migration requires cells to move through dense extracellular matrix and mesoderm to reach targets throughout the vertebrate embryo. Here, we use high-resolution microscopy, computational modeling, and in vitro and in vivo cell invasion assays to investigate the function of Aquaporin-1 (AQP-1) signaling. We find that migrating cranial neural crest cells express AQP-1 mRNA and protein within cell filopodia, implicating a biological role for water channel protein function during invasion. Differential AQP-1 levels affect neural crest cell speed, direction, and the length and stability of cell filopodia. Further, AQP-1 enhances matrix metalloprotease (MMP) activity and phosphorylated focal adhesion kinases (pFAK). Co-localization of AQP-1 expression with EphB guidance receptors in the same migrating neural crest cells raises novel implications for the concept of guided bulldozing by lead cells during migration.
Project description:Truncating mutations of CHD8, encoding a chromodomain helicase, and of many other genes with diverse functions, are strong-effect risk factors for autism spectrum disorder (ASD), suggesting multiple mechanisms of pathogenesis. We explored the transcriptional networks that CHD8 regulates in neural progenitor cells (NPCs) by reducing its expression and then integrating transcriptome sequencing (RNA-seq) with genome-wide CHD8 binding (ChIP-seq). Suppressing CHD8 to levels comparable with loss of a single allele caused altered expression of 1,756 genes, 64.9% of which were up-regulated. CHD8 showed widespread binding to chromatin, with 7,324 replicated sites that marked 5,658 genes. Integration of these data suggests that a limited array of direct regulatory effects of CHD8 produced a much larger network of secondary expression changes. Genes indirectly down-regulated (i.e., without CHD8 binding sites) reflect pathways involved in brain development, including synapse formation, neuron differentiation, cell adhesion, and axon guidance, whereas CHD8-bound genes are strongly associated with chromatin modification and transcriptional regulation. Genes associated with ASD were strongly enriched among indirectly down-regulated loci (pM-BM- =M-BM- 1.01x10-9) and CHD8-bound genes (p = 4.34x10-3), which align with previously identified co-expression modules during fetal development. We also find an intriguing enrichment of cancer related gene-sets among CHD8-bound genes (p < 1.9x10-11). In vivo suppression of chd8 in zebrafish produced macrocephaly comparable to that of humans with inactivating mutations. These data indicate that heterozygous disruption of CHD8 precipitates a network of gene expression changes involved in neurodevelopmental pathways in which many ASD-associated genes may converge on shared mechanisms of pathogenesis. ChIP-seq for CHD8 using three different antibodies, and the related protein CHD7, in human iPSC-derived NPCs treated with shRNA targeting GFP (which were used as control cells for an shRNA knockdown RNA-seq experiment that was part of the overall study)