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Expression and Metabolic Profiles in a Panel of Five Neural Tube Defect Mouse Models

ABSTRACT: Neural tube defects (NTDs) are serious birth defects with an estimated worldwide incidence of 1 per 1,000 live births. The multifactorial nature of NTDs in humans has made it difficult to elucidate pathogenesis mechanisms. However, a strong relationship has been established between folate-homocysteine metabolism and NTD risk. Prevention of a substantial proportion of fetal NTDs can be achieved through maternal folic acid (FA) supplementation. However the mechanism by which FA exerts its beneficial effect remains unclear. METHODS: To improve our understanding of the underlying mechanisms of NTD pathogenesis and the ways in which folate exerts its beneficial effect, we analyzed mRNA profiles as well as folate and vitamin B12 levels in five NTD mouse mutants whose response to dietary FA was previously established. RESULTS: Differentially expressed genes representing the effect of each NTD-causing mutation were identified and associated with biologic pathways. Interestingly, the panel of NTD mutants collectively revealed pathways related to two nuclear receptors, retinoid X receptor (RXR) and pregnane X receptor (PXR), suggesting that these pathways may be related to a shared mechanism of NTD development. Moreover, the NTD-causing mutations that were associated with FA responsiveness had expression profiles that were related to folate-homocysteine metabolic pathways. These pathways were not strongly associated with mutants that do not respond to FA supplementation, implying that FA may be beneficial when the NTD mutation affects pathways related to folate-homocysteine metabolism.

ORGANISM(S): Mus musculus

PROVIDER: GSE51285 | GEO | 2013/09/30

SECONDARY ACCESSION(S): PRJNA222308

REPOSITORIES: GEO

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Project description:Background & Aims: Previous studies have suggested that dietary folic acid (FA) can protect against certain types of cancers. However, the findings have varied and the mechanisms by which this vitamin exerts chemopreventive effects remain to be clarified. We examined the effects of FA supplementation on DNA methylation, gene expression and gastric dysplasia in a transgenic mouse model that is etiologically and histologically well matched with human gastric cancers. Methods: Hypergastrinemic mice (INS-GAS) infected with Helicobacter felis were studied at multiple stages of gastric dysplasia and early cancer, with FA supplementation initiated both at weaning and later in life. Global DNA methylation was assessed by a methylation-sensitive cytosine incorporation assay, bisulfite pyrosequencing of B1 repetitive elements and immunohistochemistry (IHC) with anti-5-methylcytosine. We also profiled gene expression in the same tissues. Results: We found a decrease in global DNA methylation and tissue folate and an increase in serum homocysteine with progression of gastric dysplasia. FA supplementation prevented this loss of global DNA methylation and markedly reduced gastric dysplasia and mucosal inflammation. FA protected against the loss of global DNA methylation both in the dysplastic gastric epithelial cells and in gastric stromal myofibroblasts. In addition, FA supplementation had an anti-inflammatory effect, as indicated by expression profiling and IHC for lymphocyte markers. Conclusions: We conclude that FA supplementation is chemopreventive in this model of Helicobacter-associated gastric cancer. The beneficial effect of FA is likely due to its ability to reverse global loss of methylation and suppress inflammation. Study the difference in gene expression between transgenic hypergastrinemic (INS-GAS) mice fed a folate-supplemented diet and a diet with normal folate content. Because folate had a substantial protective effect, we matched the animals not only by folate status but also by dysplasia score (DYS). The degree of dysplasia was scored on a 1-4 scale. True replicates are not included. The first five samples are from folate supplemented animals, and the latter five are from controls on regular chow.

Project description:Background: In the early stage of embryonic development, the neural tube (NT) cannot be closed properly due to some complex factors such as, environmental factors, genetic factors and the relationship between various factors, leading to the occurrence of neural tube defects (NTDs). Methods: In this study, we induced the mouse model of NTDs by feeding mice a low-folate diet and injecting 1.5mg/kg methotrexate on E7.5. Fetal mice were achieved at E13.5, then we extracted proteins from brain tissue with trypsin digestion. After enzymatic digestion, peptides were labeled with TMT/iTRAQ and then separated in high-performance liquid chromatography (HPLC) for subsequent LC-MS/MS analysis. To analyze the functional enrichment of differentially expressed proteins(DEPs) in the NTDs mice tissues with low folate induction, we used Gene Ontology(GO) and Kyoto Encyclopedia of Genes and Genomes(KEGG) pathway annotation to analyze proteomic changes. Results: Low folate induced mouse model was successfully constructed. Folate was used as a sensitizing agent, the teratogenicity rate of the NTDs fetal mice was increased to 36.5% when methotrexate was injected to maternal mice at E7.5. 6614 proteins were identified by mass spectrometry, among them, 5656 proteins were quantified. In the following proteomic analysis, GO classification and KEGG pathway enrichment analysis were conducted, and heatmaps were drawn for differentially expressed proteins(DEPs). Moreover, the main pathways associated with NTDs, such as Hedgehog, Wnt, p53, Hippo signaling pathways, and one carbon pool by folate, can be identified through the generation of a protein-protein interaction (PPI) network. It was also found that the regulation of ribosomal proteins has a certain impact on neural tube development, such as RPL13 and RPL14, which are upregulated in NTDs. Conclusions: Our results revealed proteomic changes in the tissues of low folate induced NTDs mice, as well as validation showed that ribosomal proteins play a regulatory role during the development of NTDs, it provides new ideas for the pathogenesis and preventive measures of NTDs.

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Expression and Metabolic Profiles in a Panel of Five Neural Tube Defect Mouse Models

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