ABSTRACT
The craniofacial disorder mandibulofacial dysostosis Guion-Almeida type is caused by haploinsufficiency of the U5 snRNP gene EFTUD2/SNU114. However, it is unclear how reduced expression of this core pre-mRNA splicing factor leads to craniofacial defects. Here we use a CRISPR-Cas9 nickase strategy to generate a human EFTUD2-knockdown cell line and show that reduced expression of EFTUD2 leads to diminished proliferative ability of these cells, increased sensitivity to endoplasmic reticulum (ER) stress and the mis-expression of several genes involved in the ER stress response. RNA-Seq analysis of the EFTUD2-knockdown cell line revealed transcriptome-wide changes in gene expression, with an enrichment for genes associated with processes involved in craniofacial development. Additionally, our RNA-Seq data identified widespread mis-splicing in EFTUD2-knockdown cells. Analysis of the functional and physical characteristics of mis-spliced pre-mRNAs highlighted conserved properties, including length and splice site strengths, of retained introns and skipped exons in our disease model. We also identified enriched processes associated with the affected genes, including cell death, cell and organ morphology and embryonic development. Together, these data support a model in which EFTUD2 haploinsufficiency leads to the mis-splicing of a distinct subset of pre-mRNAs with a widespread effect on gene expression, including altering the expression of ER stress response genes and genes involved in the development of the craniofacial region. The increased burden of unfolded proteins in the ER resulting from mis-splicing would exceed the capacity of the defective ER stress response, inducing apoptosis in cranial neural crest cells that would result in craniofacial abnormalities during development.
Subject(s)
Mandibulofacial Dysostosis/genetics , Peptide Elongation Factors/genetics , Ribonucleoprotein, U5 Small Nuclear/genetics , CRISPR-Cas Systems , Cell Proliferation/genetics , Craniofacial Abnormalities/genetics , Endoplasmic Reticulum Stress/genetics , Exons , Gene Expression/genetics , Gene Expression Regulation, Developmental/genetics , HEK293 Cells , Haploinsufficiency/genetics , Humans , Introns , Mutation , Peptide Elongation Factors/metabolism , Phenotype , RNA Precursors/metabolism , RNA Splicing/genetics , Ribonucleoprotein, U5 Small Nuclear/metabolism , Sequence Analysis, RNA/methods , Spliceosomes/geneticsABSTRACT
Heart is the first mesodermal organ to develop and is sensitive to life-threatening toxic effects of drugs during development. A number of methods have been devised to study developmental cardiotoxic effects of drugs including micromass system. The micromass system involves the culture of primary embryonic cells and reestablishment of tissue system in vitro. In chick embryonic cardiomyocyte micromass system the chick heart cells are cultured in a small volume at a very high cell density. These cells form synchronized contracting foci. Addition of drugs to this system allows us to study the developmental cardiotoxic effects at molecular level. Using appropriate end points and molecular marker or adopting high-throughput screening, this method can further help to identify and avoid the use of cardiotoxic compounds during development.
Subject(s)
Cardiotoxicity , Cell Differentiation , Embryonic Stem Cells/pathology , Heart/embryology , Myocytes, Cardiac/pathology , Toxicity Tests/methods , Animals , Cells, Cultured , Chick Embryo , Chickens , Embryonic Stem Cells/drug effects , Heart/drug effects , Myocytes, Cardiac/drug effectsABSTRACT
Hair follicle morphogenesis depends on Wnt, Shh, Notch, BMP and other signaling pathways interplay between epithelial and mesenchymal cells. The Wnt pathway plays an essential role during hair follicle induction, Shh is involved in morphogenesis and late stage differentiation, Notch signaling determines stem cell fate while BMP is involved in cellular differentiation. The Wnt pathway is considered to be the master regulator during hair follicle morphogenesis. Wnt signaling proceeds through EDA/EDAR/NF-κB signaling. NF-κB regulates the Wnt pathway and acts as a signal mediator by upregulating the expression of Shh ligand. Signal crosstalk between epithelial and mesenchymal cells takes place mainly through primary cilia. Primary cilia formation is initiated with epithelial laminin-511 interaction with dermal ß-1 integrin, which also upregulates expression of downstream effectors of Shh pathway in dermal lineage. PDGF signal transduction essential for crosstalk is mediated through epithelial PDGF-A and PDGFRα expressed on the primary cilia. Dermal Shh and PDGF signaling up-regulates dermal noggin expression; noggin is a potent inhibitor of BMP signaling which helps in counteracting BMP mediated ß-catenin inhibition. This interplay of signaling between the epithelial and dermal lineage helps in epithelial Shh signal amplification. The dermal Wnt pathway helps in upregulation of epithelial Notch expression. Dysregulation of these pathways leads to certain abnormalities and in some cases even tumor outgrowth.
