Noncanonical function of folate through folate receptor 1 during neural tube formation.

Folate supplementation reduces the occurrence of neural tube defects (NTDs), birth defects consisting in the failure of the neural tube to form and close. The mechanisms underlying NTDs and their prevention by folate remain unclear. Here we show that folate receptor 1 (FOLR1) is necessary for the formation of neural tube-like structures in human-cell derived neural organoids. FOLR1 knockdown in neural organoids and in Xenopus laevis embryos leads to NTDs that are rescued by pteroate, a folate precursor that is unable to participate in metabolism. We demonstrate that FOLR1 interacts with and opposes the function of CD2-associated protein, molecule essential for apical endocytosis and turnover of C-cadherin in neural plate cells. In addition, folates increase Ca2+ transient frequency, suggesting that folate and FOLR1 signal intracellularly to regulate neural plate folding. This study identifies a mechanism of action of folate distinct from its vitamin function during neural tube formation.

Loss of SHROOM3 affects neuroepithelial cell shape through regulating cytoskeleton proteins in cynomolgus monkey organoids.

Neural tube defects (NTDs) are severe congenital neurodevelopmental disorders arising from incomplete neural tube closure. Although folate supplementation has been shown to mitigate the incidence of NTDs, some cases, often attributable to genetic factors, remain unpreventable. The SHROOM3 gene has been implicated in NTD cases that are unresponsive to folate supplementation; at present, however, the underlying mechanism remains unclear. Neural tube morphogenesis is a complex process involving the folding of the planar epithelium of the neural plate. To determine the role of SHROOM3 in early developmental morphogenesis, we established a neuroepithelial organoid culture system derived from cynomolgus monkeys to closely mimic the in vivo neural plate phase. Loss of SHROOM3 resulted in shorter neuroepithelial cells and smaller nuclei. These morphological changes were attributed to the insufficient recruitment of cytoskeletal proteins, namely fibrous actin (F-actin), myosin II, and phospho-myosin light chain (PMLC), to the apical side of the neuroepithelial cells. Notably, these defects were not rescued by folate supplementation. RNA sequencing revealed that differentially expressed genes were enriched in biological processes associated with cellular and organ morphogenesis. In summary, we established an authentic in vitro system to study NTDs and identified a novel mechanism for NTDs that are unresponsive to folate supplementation.

Effects of Zinc Oxide Nanoparticles on Neural Tube Development in Early Chicken Embryos.

AIM: To investigate the effect of zinc oxide nanoparticles (ZnO-NPs) on neural tube development in early chicken embryos. MATERIAL AND METHODS: Fifty pathogen-free fertilized eggs were initially incubated for thirty hours. The eggs were divided into 5 groups. In the control group (C) the egg?s apex was opened and closed without any administration. In the distilled water group (DW), 10 microliters of distilled water were injected into the sub-blastodermic area. ZnO-NP suspensions were prepared in distilled water and injected sub-blastodermically into the low, medium and high dose ZnO-NP groups (10 mg/kg, 30 mg/kg, and 50 mg/kg, respectively). Incubation was completed in 72 hours, and embryological and neural tube development was evaluated histologically with a light microscope. RESULTS: Embryos in all groups were evaluated according to the Hamburger-Hamilton (HH) staging. It was observed that the staging progressed by the developmental process between 68-72 hours, which is equivalent to the 19-20th stage of HH. Differentiated otic vesicle, optic cup, lens vesicle, pharynx, and Rathke?s pouch were all observed in embryo sections. Both forebrain and hindbrain vesicles were easily distinguished in the sections by cranial flexion. Neural tube closure defect was not detected in any of the groups. CONCLUSION: In our observations, ZnO-NPs did not affect neural tube development at the applied dose ranges. We believe that additional studies with higher doses using a higher number of subjects will help clarify the conflicting data in the literature.

Effects of Myopia and Glaucoma on the Neural Canal and Lamina Cribrosa Using Optical Coherence Tomography.

PRCIS: Glaucoma was associated with axial bowing and rotation of Bruchs membrane opening (BMO) and anterior laminar insertion (ALI), skewed neural canal, and deeper anterior lamina cribrosa surface (ALCS). Longer axial length was associated with wider, longer, and more skewed neural canal and flatter ALCS. PURPOSE: Investigate the effects of myopia and glaucoma in the prelaminar neural canal and anterior lamina cribrosa using 1060-nm swept-source optical coherence tomography. PATIENTS: 19 control (38 eyes) and 38 glaucomatous subjects (63 eyes). MATERIALS AND METHODS: Participants were imaged with swept-source optical coherence tomography, and the images were analyzed for the BMO and ALI dimensions, prelaminar neural canal dimensions, and ALCS depth. RESULTS: Glaucomatous eyes had more bowed and nasally rotated BMO and ALI, more horizontally skewed prelaminar neural canal, and deeper ALCS than the control eyes. Increased axial length was associated with a wider, longer, and more horizontally skewed neural canal and a decrease in the ALCS depth and curvature. CONCLUSION: Our findings suggest that glaucomatous posterior bowing or cupping of lamina cribrosa can be significantly confounded by the myopic expansion of the neural canal. This may be related to higher glaucoma risk associated with myopia from decreased compliance and increased susceptibility to IOP-related damage of LC being pulled taut.

Cannabidiol impairs neural tube closure in mouse whole embryo culture.

BACKGROUND: Cannabidiol (CBD) is a nonpsychoactive constituent of cannabis widely available as a dietary supplement. Previous reports that it impairs the retinoid, sonic hedgehog, and folate metabolism pathways raise concern that it may impair closure of the embryonic neural tube (NT), producing NT defects including spina bifida and exencephaly. METHODS: We undertook teratogenicity testing of CBD in mouse whole embryo culture. RESULTS: At concentrations that do not diminish embryo viability, growth, or axial rotation, CBD dose-dependently impairs cranial NT closure, increasing the proportion of embryos that develop exencephaly. It concomitantly diminishes closure of the spinal NT, the posterior neuropore (PNP), producing longer neuropores at the end of culture which is a hallmark of spina bifida risk. Exposure to CBD does not disrupt the formation of long F-actin cables in surface ectoderm cells flanking the PNP or folding of the neuroepithelium at predictable hinge points. At the cellular level, CBD exposure does not alter proliferation or apoptosis of the spinal neuroepithelium. DISCUSSION: Thus, CBD acts selectively as a neuroteratogen predisposing to spina bifida and exencephaly in mouse whole embryo culture at exposure levels not associated with overt toxicity. Large-scale testing of CBD's effects on NT closure, particularly in at-risk groups, is warranted to inform its marketing to women of childbearing age.

Construction of a Mex3c Gene-Deficient Mouse Model to Study C-FOS Expression in Hypothalamic Nuclei and Observe Morphological Differences in Embryonic Neural Tube Development.

BACKGROUND This study utilized CRISPR/Cas9 gene editing technology to construct a Mex3c gene-deficient mouse model, and studied C-FOS expression in hypothalamic nuclei. MATERIAL AND METHODS Thirty Mex3c-/+ mice, 30 mice in the normal group, and 30 Mex3c-/+ mice were randomly divided into control, leptin, and ghrelin groups according to different intraperitoneal injections. HE and Nissl staining were performed to observe the morphology of hypothalamic nerve cells. The C-FOS expression in hypothalamic nuclei of each group was analyzed by immunohistochemical techniques. HE staining was used to observe neural tube morphology, and LFB staining was used to observe nerve myelin sheath morphology. TEM was used to observe neuronal ultrastructure and immunohistochemical techniques were utilized to analyze nestin expression. RESULTS C-FOS expression was lower in the normal control group than in the leptin and ghrelin groups. The Mex3c control group and the leptin group had higher C-FOS expression than the ghrelin group. In neural tube studies, no significant differences were found in the neural tube pathological sections of E14.5-day embryos in each group. Nestin results demonstrated lower expression in the normal group and there was little difference between the HD and Mex3c groups. CONCLUSIONS Mex3c appears to participate in the regulation of energy metabolism by inducing C-FOS expression in the hypothalamus. The neural tubes of the offspring of Mex3c-/+ mice had defects during development.

Effects of Erythrosine on Neural Tube Development in Early Chicken Embryos.

OBJECTIVE: Erythrosine (E127), a synthetic food dye containing iodine and sodium, has often been used inside packaged foods and beverages in Turkey and many other countries. We evaluated the effects of erythrosine on neural tube development in early-stage chicken embryos. METHODS: The study included 4 groups, with a total of 80 embryos: a control group, a normal saline group, a half-dose group, and a high-dose group. After 30 hours of incubation, saline and erythrosine solution was injected under the embryonic discs. At the end of 72 hours, the embryos were excised and evaluated macroscopically and histopathologically. RESULTS: Neural tube defects were detected in the erythrosine-administered groups with statistically significant differences. In contrast, the embryos in the control and saline groups displayed normal development. CONCLUSIONS: Erythrosine increased the risk of neural tube defects in early-stage chicken embryos, even at half of the approved dose.

The role of folic acid in preventing neural tube defects in Iraqi pregnant women: A cross sectional study

Folate deficiency in pregnant has been linked to neural tube defects in a substantial to neural tube defects in a substantial amount of medical literatures and has become a well-known fact among doctors; however, the knowledge of pregnant ladies about this association is poorly evaluated in our community. Vitamin and mineral deficiency is common among people in developing countries;however, the awareness of those people about such deficits and their associating compications is lacking. This study was conducted to evaluate the knowledge, attitude and practice of a cohort of pregnant ladies in Al-Diwaniyiah province in Mid-Euphrates region in Iraq. The present cross sectional study included 30 pregnant ladies. The study started on November 2018 and ended on January 2019. The study was carried out inAl-Diwaniyah maternity and child teaching hospital in Al-Diwaniyah province in Mid-Euphrates region, Iraq. The knowledge, attitude and practice of women regardin folie acid supplementation during early pregnancy was assessed according to 7 knowledge questions, 5 attitude questions and 5 practice questions. These questions and the demopgraphic data concerning women enrolled in the current study were obtained. The results of current study revealed poor knowledge about the advantage of folic acid in preventing congenital abnormalities was very obvious since ost of responses to the 7 questions concerning knowledge domain were within strongy disagreeing, disagree and neutral scores. Majority of response within attitude domain were in the form of disagree and strongly disagree. No correlation was found between any of the demain and the demographic characteristies of the study sample. Current study concluded that in Iraqi community, the knowledge and attitude of women toward the benefit of folie acid during early pregnancy in preventing neural tube defect iis poor; however, they practice well with this regard not due to their knowledge but because of the policy adopted by governmental antenatal care clinics and institutes (AU)

The effect of diclofenac sodium on neural tube development in the early stage of chick embryos.

BACKGROUND: Neural tube defects are congenital malformations of the central nervous system. Genetic predisposition and some environmental factors play an important role in the development of neural tube defects. This study aimed to investigate the effects of diclofenac sodium on the neural tube development in a chick embryo model that corresponds to the first month of vertebral deve- lopment in mammals. MATERIALS AND METHODS: Seventy-five fertile, specific pathogen-free eggs were incubated for 28 h and were divided into five groups of 15 eggs each. Diclofenac sodium was administered via the sub-blastodermic route at this stage. Incubation was continued till the end of the 48th h. All eggs were then opened and embryos were dissected from embryonic membranes and evaluated morphologically and histopathologically. RESULTS: It was determined that the use of increasing doses of diclofenac sodium led to defects of midline closure in early chicken embryos. There were statistically significant differences in neural tube positions (open or close) among the groups. In addition; crown-rump length, somite number were significantly decreased in high dose experimental groups compared with control group. CONCLUSIONS: This study showed that development of neurons is affected in chi- cken embryos after administration of diclofenac sodium. The exact teratogenic mechanism of diclofenac sodium is not clear; therefore it should be investigated.

Formate rescues neural tube defects caused by mutations in Slc25a32.

Periconceptional folic acid (FA) supplementation significantly reduces the prevalence of neural tube defects (NTDs). Unfortunately, some NTDs are FA resistant, and as such, NTDs remain a global public health concern. Previous studies have identified SLC25A32 as a mitochondrial folate transporter (MFT), which is capable of transferring tetrahydrofolate (THF) from cellular cytoplasm to the mitochondria in vitro. Herein, we show that gene trap inactivation of Slc25a32 (Mft) in mice induces NTDs that are folate (5-methyltetrahydrofolate, 5-mTHF) resistant yet are preventable by formate supplementation. Slc25a32gt/gt embryos die in utero with 100% penetrant cranial NTDs. 5-mTHF supplementation failed to promote normal neural tube closure (NTC) in mutant embryos, while formate supplementation enabled the majority (78%) of knockout embryos to complete NTC. A parallel genetic study in human subjects with NTDs identified biallelic loss of function SLC25A32 variants in a cranial NTD case. These data demonstrate that the loss of functional Slc25a32 results in cranial NTDs in mice and has also been observed in a human NTD patient.

Deficient Vitamin E Uptake During Development Impairs Neural Tube Closure in Mice Lacking Lipoprotein Receptor SR-BI.

SR-BI is the main receptor for high density lipoproteins (HDL) and mediates the bidirectional transport of lipids, such as cholesterol and vitamin E, between these particles and cells. During early development, SR-BI is expressed in extraembryonic tissue, specifically in trophoblast giant cells in the parietal yolk sac. We previously showed that approximately 50% of SR-BI-/- embryos fail to close the anterior neural tube and develop exencephaly, a perinatal lethal condition. Here, we evaluated the role of SR-BI in embryonic vitamin E uptake during murine neural tube closure. Our results showed that SR-BI-/- embryos had a very low vitamin E content in comparison to SR-BI+/+ embryos. Whereas SR-BI-/- embryos with closed neural tubes (nSR-BI-/-) had high levels of reactive oxygen species (ROS), intermediate ROS levels between SR-BI+/+ and nSR-BI-/- embryos were detected in SR-BI-/- with NTD (NTD SR-BI-/-). Reduced expression of Pax3, Alx1 and Alx3 genes was found in NTD SR-BI-/- embryos. Maternal α-tocopherol dietary supplementation prevented NTD almost completely (from 54% to 2%, p < 0.001) in SR-BI-/- embryos and normalized ROS and gene expression levels. In sum, our results suggest the involvement of SR-BI in the maternal provision of embryonic vitamin E to the mouse embryo during neural tube closure.

Nutritional role of folate.

Folate functions as a coenzyme to transfer one-carbon units that are necessary for deoxythymidylate synthesis, purine synthesis, and various methylation reactions. Ingested folate becomes a functional molecule through intestinal absorption, circulation, transport to cells, and various modifications to its structure. Associations between nutritional folate status and chronic diseases such as cardiovascular disease, cancer, and cognitive dysfunction have been reported. It has also been reported that maternal folate nutritional status is related to the risk of neural tube defects (NTDs) in the offspring. It has also been recommended that folate be consumed in the diet to promote the maintenance of good health. To reduce the risk of NTDs, supplementation with folic acid (a synthetic form of folate) during the periconceptional period has also been recommended. This paper describes the basic features and nutritional role of folate.

Folate-dependent methylation of septins governs ciliogenesis during neural tube closure.

Periconception maternal folic acid (vitamin B9) supplementation can reduce the prevalence of neural tube defects (NTDs), although just how folates benefit the developing embryo and promote closing of the neural tube and other morphologic processes during development remains unknown. Folate contributes to a 1-carbon metabolism, which is essential for purine biosynthesis and methionine recycling and affects methylation of DNA, histones, and nonhistone proteins. Herein, we used animal models and cultured mammalian cells to demonstrate that disruption of the methylation pathway mediated by folate compromises normal neural tube closure (NTC) and ciliogenesis. We demonstrate that the embryos with NTD failed to adequately methylate septin2, a key regulator of cilium structure and function. We report that methylation of septin2 affected its GTP binding activity and formation of the septin2-6-7 complex. We propose that folic acid promotes normal NTC in some embryos by regulating the methylation of septin2, which is critical for normal cilium formation during early embryonic development.-Toriyama, M., Toriyama, M., Wallingford, J. B., Finnell, R. H. Folate-dependent methylation of septins governs ciliogenesis during neural tube closure.

Folate receptors and neural tube closure.

Neural tube defects (NTD) are among the most common human congenital malformations, affecting 0.5-8.0/1000 of live births. Human clinical trials have shown that periconceptional folate supplementation significantly decreases the occurrence of NTD in offspring. However, the mechanism by which folate acts on NTD remains largely unknown. Folate receptor (Folr) is one of the three membrane proteins that mediate cellular uptake of folates. Recent studies suggest that mouse Folr1 (formerly referred to as Fbp1) is essential for neural tube closure. Therefore, we examined spatial and temporal expression patterns of Folr1 in developing mouse embryos, showing a close association between Folr1 and anterior neural tube closure. Transient transgenic analysis was performed using lacZ as a reporter; we identified a 1.1-kb enhancer that directs lacZ expression in the neural tube and optic vesicle in a manner that is similar to endogenous Folr1. The 1.1-kb enhancer sequences were highly conserved between humans and mice, suggesting that human FOLR1 is associated with anterior neural tube closure in humans. Several experimental studies in mice and human epidemiological and genetics studies have suggested that folate receptor abnormalities are involved in a portion of human NTDs, although the solo defect of FOLR1 did not cause NTD.

Folate receptor 1 is necessary for neural plate cell apical constriction during Xenopus neural tube formation.

Folate supplementation prevents up to 70% of neural tube defects (NTDs), which result from a failure of neural tube closure during embryogenesis. The elucidation of the mechanisms underlying folate action has been challenging. This study introduces Xenopus laevis as a model to determine the cellular and molecular mechanisms involved in folate action during neural tube formation. We show that knockdown of folate receptor 1 (Folr1; also known as FRα) impairs neural tube formation and leads to NTDs. Folr1 knockdown in neural plate cells only is necessary and sufficient to induce NTDs. Folr1-deficient neural plate cells fail to constrict, resulting in widening of the neural plate midline and defective neural tube closure. Pharmacological inhibition of folate action by methotrexate during neurulation induces NTDs by inhibiting folate interaction with its uptake systems. Our findings support a model in which the folate receptor interacts with cell adhesion molecules, thus regulating the apical cell membrane remodeling and cytoskeletal dynamics necessary for neural plate folding. Further studies in this organism could unveil novel cellular and molecular events mediated by folate and lead to new ways of preventing NTDs.

Prevention of neural tube defects in Lrp2 mutant mouse embryos by folic acid supplementation.

BACKGROUND: Neural tube defects (NTDs) are among the most common structural birth defects in humans and are caused by the complex interaction of genetic and environmental factors. Periconceptional supplementation with folic acid can prevent NTDs in both mouse models and human populations. A better understanding of how genes and environmental factors interact is critical toward development of rational strategies to prevent NTDs. Low density lipoprotein-related protein 2 (Lrp2) is involved in endocytosis of the folic acid receptor among numerous other nutrients and ligands. METHODS: We determined the effect of iron and/or folic acid supplementation on the penetrance of NTDs in the Lrp2null mouse model. The effects of supplementation on folate and iron status were measured in embryos and dams. RESULTS: Periconceptional dietary supplementation with folic acid did not prevent NTDs in Lrp2 mutant embryos, whereas high levels of folic acid supplementation by intraperitoneal injection reduced incidence of NTDs. Importantly, Lrp2null/+ dams had reduced blood folate levels that improved with daily intraperitoneal injections of folate but not dietary supplementation. On the contrary, iron supplementation had no effect on the penetrance of NTDs in Lrp2 mutant embryos and negated the preventative effect of folic acid supplementation in Lrp2null/null mutants. CONCLUSION: Lrp2 is required for folate homeostasis in heterozygous dams and high levels of supplementation prevents NTDs. Furthermore, high levels of dietary iron supplementation interfered with folic acid supplementation negating the positive effects of supplementation in this model. Birth Defects Research 109:16-26, 2017. © 2016 The Authors Birth Defects Published by Wiley Periodicals, Inc.

Metabolite profiling of whole murine embryos reveals metabolic perturbations associated with maternal valproate-induced neural tube closure defects.

BACKGROUND: Valproic acid (VPA) is prescribed therapeutically for multiple conditions, including epilepsy. When taken during pregnancy, VPA is teratogenic, increasing the risk of several birth and developmental defects including neural tube defects (NTDs). The mechanism by which VPA causes NTDs remains controversial and how VPA interacts with folic acid (FA), a vitamin commonly recommended for the prevention of NTDs, remains uncertain. We sought to address both questions by applying untargeted metabolite profiling analysis to neural tube closure (NTC) stage mouse embryos. METHODS: Pregnant SWV dams on either a 2 ppm or 10 ppm FA supplemented diet were injected with a single dose of VPA on gestational day E8.5. On day E9.5, the mouse embryos were collected and evaluated for NTC status. Liquid chromatography coupled to mass spectrometry metabolomics analysis was performed to compare metabolite profiles of NTD-affected VPA-exposed whole mouse embryos with profiles from embryos that underwent normal NTC from control dams. RESULTS: NTDs were observed in all embryos from VPA-treated dams and penetrance was not diminished by dietary FA supplementation. The most profound metabolic perturbations were found in the 10ppm FA VPA-exposed mouse embryos, compared with the other three treatment groups. Affected metabolites included amino acids, nucleobases and related phosphorylated nucleotides, lipids, and carnitines. CONCLUSION: Maternal VPA treatment markedly perturbed purine and pyrimidine metabolism in E9.5 embryos. In combination with a high FA diet, VPA treatment resulted in gross metabolic changes, likely caused by a multiplicity of mechanisms, including an apparent disruption of mitochondrial beta-oxidation. Birth Defects Research 109:106-119, 2017. © 2016 Wiley Periodicals, Inc.

High levels of iron supplementation prevents neural tube defects in the Fpn1ffe mouse model.

BACKGROUND: Periconception maternal nutrition and folate in particular are important factors influencing the incidence of neural tube defects (NTDs). Many but not all NTDs are prevented by folic acid supplementation and there is a pressing need for additional strategies to prevent these birth defects. Other micronutrients such as iron are potential candidates, yet a clear role for iron deficiency in contributing to NTDs is lacking. Our previous studies with the flatiron (ffe) mouse model of Ferroportin1 (Fpn1) deficiency suggest that iron is required for neural tube closure and forebrain development raising the possibility that iron supplementation could prevent NTDs. METHODS: We determined the effect of periconception iron and/or folic acid supplementation on the penetrance of NTDs in the Fpn1ffe mouse model. Concurrently, measurements of folate and iron were made to ensure supplementation had the intended effects. RESULTS: High levels of iron supplementation significantly reduced the incidence of NTDs in Fpn1ffe mutants. Fpn1 deficiency resulted in reduced folate levels in both pregnant dams and embryos. Yet folic acid supplementation did not prevent NTDs in the Fpn1ffe model. Similarly, forebrain truncations were rescued with iron. Surprisingly, the high levels of iron supplementation used in this study caused folate deficiency in wild-type dams and embryos. CONCLUSION: Our results demonstrate that iron supplementation can prevent NTDs and forebrain truncations in the Fpn1ffe model. Surprisingly, high levels of iron supplementation and iron overload can cause folate deficiency. If iron is essential for neural tube closure, it is possible that iron deficiency might contribute to NTDs. Birth Defects Research 109:81-91, 2017. © 2016 The Authors Birth Defects Research Published by Wiley Periodicals, Inc.