The role of MEG3 in the proliferation of palatal mesenchymal cells is related to the TGFβ/Smad pathway in TCDD inducing cleft palate

TCDD dysregulation of lncRNA expression, liver zonation and intercellular communication across the liver lobule

The persistent environmental aryl hydrocarbon receptor agonist and hepatotoxin TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) induces hepatic lipid accumulation (steatosis), inflammation (steatohepatitis) and fibrosis. Thousands of liver-expressed, nuclear-localized lncRNAs with regulatory potential have been identified; however, their roles in TCDD-induced hepatoxicity and liver disease are unknown. We analyzed single nucleus (sn)RNA-seq data from control and subchronic (4 wk) TCDD-exposed mouse liver to determine liver cell-type specificity, zonation and differential expression profiles for thousands of lncRNAs. TCDD dysregulated >4000 of these lncRNAs in one or more liver cell types, including 684 lncRNAs specifically dysregulated in liver non-parenchymal cells. Trajectory inference analysis revealed major disruption by TCDD of hepatocyte zonation, affecting >800 genes, including 121 lncRNAs, with strong enrichment for lipid metabolism genes. TCDD also dysregulated expression of >200 transcription factors, including 19 Nuclear Receptors, most notably in hepatocytes and Kupffer cells. TCDD-induced changes in cell-cell communication patterns included marked decreases in EGF signaling from hepatocytes to non-parenchymal cells and increases in extracellular matrix-receptor interactions central to liver fibrosis. Gene regulatory networks constructed from the snRNA-seq data identified TCDD-exposed liver network-essential lncRNA regulators linked to functions such as fatty acid metabolic process, peroxisome and xenobiotic metabolism. Networks were validated by the striking enrichments that predicted regulatory lncRNAs showed for specific biological pathways. These findings highlight the power of snRNA-seq to discover functional roles for many xenobiotic-responsive lncRNAs in both hepatocytes and liver non-parenchymal cells and to elucidate novel aspects of foreign chemical-induced hepatotoxicity and liver disease, including dysregulation of intercellular communication within the liver lobule.

Role of lncRNAs and circRNAs in Orofacial Clefts

Different modes of gene regulation, such as histone modification, transcription factor binding, DNA methylation, and microRNA (miRNA) expression, are critical for the spatiotemporal expression of genes in developing orofacial tissues. Aberrant regulation in any of these modes may contribute to orofacial defects. Noncoding RNAs (ncRNAs), such as long ncRNAs (lncRNAs) and circular RNAs (circRNAs), have been shown to alter miRNA expression, and are thus emerging as novel contributors to gene regulation. Some of these appear to function as 'miRNA sponges', thereby diminishing the availability of these miRNAs to inhibit the expression of target genes. Such ncRNAs are also termed competitive endogenous RNAs (ceRNAs). Here, we examine emerging data that shed light on how lncRNAs and circRNAs may alter miRNA regulation, thus affecting orofacial development and potentially contributing to orofacial clefting.

Comprehensive analysis of plasma miRNA and related ceRNA network in non-syndromic cleft lip and/or palate

BACKGROUND

Non-syndromic cleft lip and/or palate (NSCL/P) is a common maxillofacial birth defect, and the etiology of which is complex and still unclear. Accumulating studies indicate that long non-coding RNAs(lncRNAs) and microRNAs(miRNAs) play important roles in NSCL/P. However, the potential regulatory associations remain largely unknown. In this study, we screened differentially expressed miRNAs and constructed competing endogenous RNA (ceRNA) networks to lay a foundation for further research on the regulatory mechanism of ncRNAs in NSCL/P.

METHODS

NSCL/P plasma RNA was analyzed by miRNA sequencing. The bioinformatics database, GEO and STRING database, GO and KEGG enrichment analysis and Cytoscape software were used to analyze and screen lncRNAs and mRNAs potentially related to differential miRNAs. The expression levels of lncRNA, miRNA and mRNA in ceRNA network were detected by RT-qPCR.

RESULTS

In NSCL/P plasma samples, there were 47 differentially expressed miRNAs in CPO group and 36 differentially expressed miRNAs in CL/P group. GO and KEGG enrichment analysis showed that cell cycle, cell response to DNA damage stimulation, and the TGF-βsignaling pathway were relevant to the formation of NSCL/P. The RT-qPCR results showed that the expression levels of lncRNA NEAT1, hsa-miR-130 b-3p, hsa-miR-212-3p, hsa-miR-200 b-3p and SMAD2 were different in NSCL/P.

CONCLUSIONS

We found that differentially expressed miR-212-3p, miR-200 b-3p and miR-130 b-3p may be involved in the pathogenesis of cleft palate by regulating related target genes.

Histological and Immunohistochemical Studies to Determine the Mechanism of Cleft Palate Induction after Palatal Fusion in Mice Exposed to TCDD

Rupture of the basement membrane in fused palate tissue can cause the palate to separate after fusion in mice, leading to the development of cleft palate. Here, we further elucidate the mechanism of palatal separation after palatal fusion in 8–10-week-old ICR female mice. On day 12 of gestation, 40 μg/kg of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), sufficient to cause cleft palate in 100% of mice, was dissolved in 0.4 mL of olive oil containing toluene and administered as a single dose via a gastric tube. Fetal palatine frontal sections were observed by H&E staining, and epithelial cell adhesion factors, apoptosis, and cell proliferation were observed from the anterior to posterior palate. TUNEL-positive cells and Ki67-positive cells were observed around the posterior palatal dissection area of the TCDD-treated group. Moreover, in fetal mice exposed to TCDD, some fetuses exhibited cleft palate dehiscence during fusion. The results suggest that palatal dehiscence may be caused by abnormal cell proliferation in epithelial tissues, decreased intercellular adhesion, and inhibition of mesenchymal cell proliferation. By elucidating the mechanism of cleavage after palatal fusion, this research can contribute to establishing methods for the prevention of cleft palate development.