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The CHARGE syndrome ortholog CHD-7 regulates TGF-b pathways in C. elegans

ABSTRACT: CHARGE syndrome is a complex developmental disorder caused by mutations in the chromodomain helicase DNA-binding protein7 (CHD7) and characterized by retarded growth and malformations in the heart and nervous system. Despite the public health relevance of this disorder, relevant cellular pathways, and targets of CHD7 that relate to disease pathology are still poorly understood. Here we report that chd-7, the nematode ortholog of Chd7, is required for dauer morphogenesis, lifespan determination, stress response and body size determination. Consistent with our discoveries, we found chd-7 to be allelic to scd-3, a previously identified dauer suppressor from the DAF-7/TGF-E pathway. Epistatic analysis places CHD-7 at the level of the DAF-3/DAF-5 complex, but we found that CHD-7 also directly impacts the expression of multiple components of this pathway. Transcriptomic analysis revealed that chd-7 mutants fail to repress daf 9 for execution of the dauer program. In addition, CHD-7 regulates the DBL-1/BMP pathway components and shares roles in male tail development and cuticle synthesis. To explore a potential conserved function for chd-7 in vertebrates, we used Xenopus laevis embryos, an established model to study craniofacial development. Morpholino mediated knockdown of Chd7 led to a reduction in col2a1 mRNA levels, a collagen whose expression depends on TGF-E signaling. Both embryonic lethality and craniofacial defects in Chd7- depleted tadpoles were partially rescued by over-expression of col2a1 mRNA. We suggest that Chd7 has conserved roles in regulation of the TGF-E signaling pathway and pathogenic Chd7 could lead to a defective extracellular matrix deposition.

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE199192 | GEO | 2022/03/23

REPOSITORIES: GEO

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Project description:Many tissue-specific stem cells maintain the ability to produce multiple cell types during long periods of non-division, or quiescence. FOXO transcription factors promote quiescence and stem cell maintenance, but the mechanisms by which FOXO proteins promote multipotency during quiescence are still emerging. The single FOXO ortholog in C. elegans, daf-16, promotes entry into a quiescent and stress-resistant larval stage called dauer in response to adverse environmental cues. During dauer, stem and progenitor cells maintain or re-establish multipotency to allow normal development to resume after dauer. We find that during dauer, daf-16/FOXO prevents epidermal stem cells (seam cells) from prematurely adopting differentiated, adult characteristics. In particular, dauer larvae that lack daf-16 misexpress collagens that are normally adult-enriched. Using col-19p::gfp as an adult cell fate marker, we find that all major daf-16 isoforms contribute to opposing col-19p::gfp expression during dauer. By contrast, daf-16(0) larvae that undergo non-dauer development do not misexpress col-19p::gfp. Adult cell fate and the timing of col-19p::gfp expression are regulated by the heterochronic gene network, including lin-41 and lin-29. lin-41 encodes an RNA-binding protein orthologous to LIN41/TRIM71 in mammals, and lin-29 encodes a conserved zinc finger transcription factor. In non-dauer development lin-41 opposes adult cell fate by inhibiting the translation of lin-29, which directly activates col-19 transcription and promotes adult cell fate. We find that during dauer, lin-41 blocks col-19p::gfp expression, but surprisingly, lin-29 is not required in this context. Additionally, daf-16 promotes the expression of lin-41 in dauer larvae. The col-19p::gfp misexpression phenotype observed in dauer larvae with reduced daf-16 requires the downregulation of lin-41, but does not require lin-29. Taken together, this work demonstrates a novel role for daf-16/FOXO as a heterochronic gene that promotes expression of lin-41/TRIM71 to contribute to multipotent cell fate in a quiescent stem cell model.

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.

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The CHARGE syndrome ortholog CHD-7 regulates TGF-b pathways in C. elegans

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