Ethionine-mediated reduction of S-adenosylmethionine is responsible for the neural tube defects in the developing mouse embryo-mediated m6A modification and is involved in neural tube defects via modulating Wnt/β-catenin signaling pathway

Neural tube defects (NTDs) remain one of the most life-threatening birth defects affecting infants. Most patients with NTDs eventually develop lifelong disability, which cause significant morbidity and mortality and seriously reduce the quality of life. Our previous study has found that ethionine inhibits cell viability by disrupting the balance between proliferation and apoptosis, and preventing neural stem cells from differentiating into neurons and astrocytes. However, how ethionine participates in the pathogenesis of neural tube development through N6-methyladenosine (m6A) modification remains unknown. This study aims to investigate METTL3- and ALKBH5-mediated m6A modification function and mechanism in NTDs. Herein, our results demonstrate that SAM play not only a compensatory role, it also leads to changes of m6A modification in neural tube development and regulation. Additionally, these data implicate that METTL3 is enriched in HT-22 cells, and METTL3 knockdown reduces cell proliferation and increases apoptosis through suppressing Wnt/β-catenin signaling pathway. Significantly, overexpression of ALKBH5 can only inhibit cell proliferation, but cannot promote cell apoptosis. This research reveals an important role of SAM in development of NTDs, providing a good theoretical basis for further research on NTDs. This finding represents a novel epigenetic mechanism underlying that the m6A modification has profound and lasting implications for neural tube development.

A connectivity signature for glioblastoma

Tumor cell extensions called tumor microtubes (TMs) in glioma resemble neurites during neurodevelopment and connect glioma cells to a network that has considerable relevance for tumor progression and therapy resistance. The determination of interconnectivity in individual tumors has been challenging and the impact of tumor cell connectivity on patient survival remained unresolved so far. Here, a connectivity signature from single-cell RNA-sequenced (scRNA-Seq) xenografted primary glioblastoma (GB) cells was established and clinically validated. Thirty-four of 40 connectivity genes were related to neurogenesis, neural tube development or glioma progression, including the TM-network-relevant GAP43 gene. Astrocytic-like and mesenchymal-like GB cells had the highest connectivity signature scores in scRNA-Seq data of patient-derived xenografts and patient samples. In 230 human GBs, high connectivity correlated with the mesenchymal expression subtype, TP53 wildtype, and with dismal patient survival. CHI3L1 was identified as a robust molecular marker of connectivity. Thus, the connectivity signature allows novel insights into brain tumor biology, provides a proof-of-principle that tumor cell connectivity is relevant for patients prognosis, and serves as a robust biomarker that can be used for future clinical trials.

Reduced H3K27me3 suppresses Wnt/β-catenin signaling by S-adenosylmethionine deficiency in neural tube development

S-adenosylmethionine (SAM) as a major methyl donor play a key role in methylation modification in vivo, and its disorder was closely related to neural tube defects (NTDs). However, the underlying mechanism between SAM deficiency and NTDs remained unclear. Here, we investigated the association between histone methylation modification and Wnt/β-catenin signaling pathway in NTDs induced by SAM deficiency. The levels of SAM and SAH were determined by enzyme linked immunosorbent assay (ELISA). The expressions of H3K27me3 and Wnt/β-catenin signaling pathway specific markers were demonstrated by western blotting, reverse transcription, and quantitative PCR (RT-qPCR) and immunofluorescence in ethionine induced E11.5 mouse NTDs and NSCs models. The results showed that the incidence rate of NTDs induced by ethionine were 46.2%, post treatment of ethionine combined with SAM, the incidence rate of NTDs was reduced to 26.2%. The level of SAM was significantly decreased (P<0.05) and a reduction in the SAM/SAH ratio was observed. The SAM depletion caused the reduction of both H3K27me3 modifications and UTX activity, and inhibited the marker proteins (β-catenin, TCF-4, Axin-2, p-GSK-3β, CyclinD1, and C-myc) in Wnt/β-catenin signaling pathway (P<0.05). The differentiations of neural stem cells (NSCs) into neurons and oligodendrocytes were inhibited under SAM deficiency (P<0.05). These results indicated that the depletion of SAM led to reduced H3K27me3 modifications, prevented the activation of Wnt/β-catenin signaling pathway and NSCs differentiation, which provided an understanding of the novel function of epigenetic regulation in NTDs.

METTL3-Mediated m6A Modification is Involved in Neural Tube Defects via Modulating Wnt/β-Catenin Signaling Pathway

Neural tube defects (NTDs) remain one of the most life-threatening birth defects affecting infants. Most patients with a NTDs eventually develop lifelong disability, which cause significant morbidity and mortality and seriously reduce the quality of life. Therefore, identifiable of novel pathogenic strategies for NTDs patients is urgently required. Increasing evidence indicates that METTL3-mediated m6A modification is present in many physiopathological processes of cell apoptosis and survival. Our results demonstrate that SAM play not only a compensatory role, SAM can also lead to m6A modification changes in neural tube development and regulation. This research provides a good theoretical basis for further research on folic acid deficiency leading to NTDs, reveals the important role of SAM in the development of NTDs, and provides new clue for clinical researchers and clinical work.

Axial elongation of caudalized human organoids mimics aspects of neural tube development

ABSTRACT Axial elongation of the neural tube is crucial during mammalian embryogenesis for anterior-posterior body axis establishment and subsequent spinal cord development, but these processes cannot be interrogated directly in humans as they occur post-implantation. Here, we report an organoid model of neural tube extension derived from human pluripotent stem cell (hPSC) aggregates that have been caudalized with Wnt agonism, enabling them to recapitulate aspects of the morphological and temporal gene expression patterns of neural tube development. Elongating organoids consist largely of neuroepithelial compartments and contain TBXT+SOX2+ neuro-mesodermal progenitors in addition to PAX6+NES+ neural progenitors. A critical threshold of Wnt agonism stimulated singular axial extensions while maintaining multiple cell lineages, such that organoids displayed regionalized anterior-to-posterior HOX gene expression with hindbrain (HOXB1) regions spatially distinct from brachial (HOXC6) and thoracic (HOXB9) regions. CRISPR interference-mediated silencing of TBXT, a Wnt pathway target, increased neuroepithelial compartmentalization, abrogated HOX expression and disrupted uniaxial elongation. Together, these results demonstrate the potent capacity of caudalized hPSC organoids to undergo axial elongation in a manner that can be used to dissect the cellular organization and patterning decisions that dictate early human nervous system development.

Reduced H3K27me3 Suppresses Wnt/β-catenin Signaling by S-adenosylmethionine Deficiency in Neural Tube Development

Background: S-adenosylmethionine as a major methyl donor play a key role in methylation modification in vivo, and its disorder was closely related to neural tube defects. However, the underlying mechanism between SAM deficiency and NTDs remained unclear.Methods: we investigated the association between histone methylation modification and Wnt/β-catenin signaling pathway in NTDs induced by SAM deficiency. The levels of SAM and SAH were determined by enzyme linked immunosorbent assay. The expressions of H3K27me3 and Wnt/β-catenin signaling pathway specific markers were demonstrated by western blotting, reverse transcription, and quantitative PCR and immunofluorescence in ethionine induced E11.5 mouse NTDs and NSCs models. Results: we found that the incidence rate of NTDs induced by ethionine were 46.2%, post treatment of ethionine combined with SAM, the incidence rate of NTDs was reduced to 26.2%. The level of SAM was significantly decreased (P<0.05) and a reduction in the SAM/SAH ratio was observed. The SAM depletion caused the reduction of both H3K27me3 modifications and UTX activity, and inhibited the marker proteins (β-catenin, TCF-4, Axin-2, p-GSK-3β, CyclinD1, and C-myc) in Wnt/β-catenin signaling pathway (P<0.05). The differentiations of neural stem cells into neurons and oligodendrocytes were inhibited under SAM deficiency (P<0.05).Conclusions: These results indicated that the depletion of SAM led to reduced H3K27me3 modifications, prevented the activation of Wnt/β-catenin signaling pathway and NSCs differentiation, which provided an understanding of the novel function of epigenetic regulation in NTDs.

The Mechanism of Fos and Leptin Receptor in Neural Tube Development of Offspring Under The Regulation of Energy Balance

Background The occurrence of neural tube defects is a complex process in which genes, internal and external environment and other factors jointly influence and occur interactively. In this experiment, animal models of different energy balance states are constructed. To explore the mechanism of fos and leptin-leptin receptor during neural tube development of offspring under different energy states and its effect on neural tube development of offspringMethods Using gene identification technology to obtain Mex3c+/- negative energy balance mice and high-fat diet to obtain positive energy balance mice, and obtain E10.5d, E12.5d, E14.5d embryos. We will verify the expression of fos, leptin, LEPR, nestin, PAX3, and H3K27me3 proteins in the neural tube of the offspring through relevant experimental methods.Results We have successfully constructed animal models, Control group (18.82g±1.54g), Mex3c group (18.84g±1.08g), HFD group (22.61g±1.10g). Neural tube HE staining showen that compared with the Control group, the neuronal maturity of the Mex3c group and the HFD group was reduced. Immunohistochemical staining showed that both fos and leptin were expressed on the nucleus, and LEPR was expressed on the cell membrane. Western blot experiments showed that compared with the Control group, the Mex3c group and the HFD group had low expression of fos protein (P＜0.01), the Mex3c group had high expression of LEPR protein (P＜0.01) and the HFD group had high expression of LEPR protein (P＜0.01). Immunostaining experiments showed that nestin was expressed in nerve fibers, and PAX3 and H3K27me3 were both expressed in the nucleus. Western blooting experiment showed that compared with the Control group, the Mex3c group had high expression of nestin protein (P＜0.01), PAX3 protein (P＜0.01), H3K27me3 (P＜0.01), and the HFD group had high expression of nestin protein (P＜0.01). ) And PAX3 protein (P<0.01), H3K27me3 (P<0.01).ConclusionsMex3c regulates leptin and LEPR by enhancing the expression of fos mRNA to participate in the neural tube development process of offspring. The neural tube nestin, PAX3, and H3K27me3 of the offspring of Mex3c+/- mice and high-fat diet mice continue to be highly expressed. Mex3c+/- mice express low leptin, and high-fat diet mice highly express leptin; preliminary reveals the regulation of different energy states Leptin-LEPR is involved in the process of neurodevelopment. Mex3c mutant mice and mice on a high-fat diet lead to decreased neurodevelopmental maturity.

Inference of Morphogen Gradient Precision from Molecular Noise Data

During development, morphogen gradients provide spatial information for tissue patterning. Gradients and readout mechanisms are inevitably variable, yet the resulting patterns are strikingly precise. Measurement limitations currently preclude precise detection of morphogen gradients over long distances. Here, we develop a new formalism to estimate gradient precision along the entire patterning axis from measurements close to the source. Using numerical simulations, we infer gradient variability from measured molecular noise levels in morphogen production, decay, and diffusion. The predicted precision is much higher than previously measured—precise enough to allow even single gradients to define the central progenitor boundaries during neural tube development. Finally, we show that the patterning mechanism is optimized for precise progenitor cell numbers, rather than precise boundary positions, as the progenitor domain size is particularly robust to gradient alterations. We conclude that single gradients can yield the observed developmental precision, which provides new prospects for tissue engineering.

The Effect of Retinoic Acid on the Development of Neural Tube at Early Stages of Chicken Embryo

Aims: this study aimed to find out the effect of application of 1.5 mg\ml of retinoic acid on chicken development at different stages of neural tube development. Methodology: thirty fertile domestic Gallus gallus eggs were divided into three groups of 10 eggs for each. These groups repeated four time for four different stages HH8, HH10, HH15 and HH18. Retinoic acid (RA) or dimethyl sulphoxide (DEMSO) was injected through the air sac, and the eggs were incubated for another 24 h. Eggs were opened after 24 or 48 h of incubation, and the embryos were evaluated morphologically and histologically. Results: The results of this experiment indicated that, In control group and DEMSO group none exhibited neural tube defects neural tube (NTDs). However group treated with 1.5mg/ml of RA exhibit sever NTDs and malformed at the head, cranial and cardiac regions. Shape of the lumen and spatial arrangement of the cell populations of floor plate and roof plate of neural tube has been changed after RA treatment. Conclusion: Association of excises RA with neural tube defects was demonstrated in the present study on neurulation process during embryogenesis.