Cellular mechanisms underlying Pax3-related neural tube defects and their prevention by folic acid

Impact of food additives on neurodevelopmental processes in zebrafish (Danio rerio): Exploring circadian clock genes and dopamine system

Assessing the impact of food additives on neurodevelopmental processes extends beyond traditional acute toxicity evaluations to address subtler, long-term effects. This study investigates the impact of common food additives (tartrazine, sunset yellow, sodium benzoate, and aspartame) on neurodevelopment in zebrafish embryos, observed from 18 hours postfertilization (hpf) to 91 days postfertilization (dpf). Results show reduced 96 hpf locomotor activity after aspartame exposure, with elevated additives correlating with decreased heart rates and induced neurodegenerative phenotypes, including bent tails and abnormal pigmentation. Although locomotor activity decreases at 7 days postexposure, a gradual recovery is observed. Transcriptome analysis indicates alterations in clock genes (Cry2 and Per2) and dopamine-related genes (NURR1 and tyrosine hydroxylase) in zebrafish larvae. Dietary additive exposure during embryonic development impacts clock genes, influencing dopamine activity and resulting in neurobehavioral changes. This study underscores potential risks associated with dietary additive exposure during critical developmental stages, warranting reconsideration of consumption guidelines, especially for expectant mothers. Observed neurodevelopmental toxicity, even below recommended levels, emphasizes the importance of safeguarding neurodevelopmental health in early life. Our findings contribute to understanding the neurotoxic effects of dietary additives, emphasizing the necessity of protecting neurodevelopment during vulnerable periods. This study is the first to demonstrate a direct correlation between food additives and the dysregulation of key circadian rhythm and dopaminergic genes in zebrafish, providing new insights into the neurodevelopmental impacts of dietary additives. These findings pave the way for further research into the molecular mechanisms and potential implications for human health.

Association of embryonic inositol status with susceptibility to neural tube defects, metabolite profile, and maternal inositol intake

Maternal nutrition contributes to gene-environment interactions that influence susceptibility to common congenital anomalies such as neural tube defects (NTDs). Supplemental myo-inositol (MI) can prevent NTDs in some mouse models and shows potential for prevention of human NTDs. We investigated effects of maternal MI intake on embryonic MI status and metabolism in curly tail mice, which are genetically predisposed to NTDs that are inositol-responsive but folic acid resistant. Dietary MI deficiency caused diminished MI in maternal plasma and embryos, showing that de novo synthesis is insufficient to maintain MI levels in either adult or embryonic mice. Under normal maternal dietary conditions, curly tail embryos that developed cranial NTDs had significantly lower MI content than unaffected embryos, revealing an association between diminished MI status and failure of cranial neurulation. Expression of inositol-3-phosphate synthase 1, required for inositol biosynthesis, was less abundant in the cranial neural tube than at other axial levels. Supplemental MI or d-chiro-inositol (DCI) have previously been found to prevent NTDs in curly tail embryos. Here, we investigated the metabolic effects of MI and DCI treatments by mass spectrometry-based metabolome analysis. Among inositol-responsive metabolites, we noted a disproportionate effect on nucleotides, especially purines. We also found altered proportions of 5-methyltetrahydrolate and tetrahydrofolate in MI-treated embryos suggesting altered folate metabolism. Treatment with nucleotides or the one-carbon donor formate has also been found to prevent NTDs in curly tail embryos. Together, these findings suggest that the protective effect of inositol may be mediated through the enhanced supply of nucleotides during neural tube closure.

Stem cell-derived models of spinal neurulation

Neurulation is a critical step in early embryonic development, giving rise to the neural tube, the primordium of the central nervous system in amniotes. Understanding this complex, multi-scale, multi-tissue morphogenetic process is essential to provide insights into normal development and the etiology of neural tube defects. Innovations in tissue engineering have fostered the generation of pluripotent stem cell-based in vitro models, including organoids, that are emerging as unique tools for delving into neurulation mechanisms, especially in the context of human development. Each model captures specific aspects of neural tube morphogenesis, from epithelialization to neural tissue elongation, folding and cavitation. In particular, the recent models of human and mouse trunk morphogenesis, such as gastruloids, that form a spinal neural plate-like or neural tube-like structure are opening new avenues to study normal and pathological neurulation. Here, we review the morphogenetic events generating the neural tube in the mammalian embryo and questions that remain unanswered. We discuss the advantages and limitations of existing in vitro models of neurulation and possible future technical developments.

Caudal Fgfr1 disruption produces localised spinal mis-patterning and a terminal myelocystocele-like phenotype in mice

Closed spinal dysraphisms are poorly understood malformations classified as neural tube (NT) defects. Several, including terminal myelocystocele, affect the distal spine. We have previously identified a NT closure-initiating point, Closure 5, in the distal spine of mice. Here, we document equivalent morphology of the caudal-most closing posterior neuropore (PNP) in mice and humans. Closure 5 forms in a region of active FGF signalling, and pharmacological FGF receptor blockade impairs its formation in cultured mouse embryos. Conditional genetic deletion of Fgfr1 in caudal embryonic tissues with Cdx2Cre diminishes neuroepithelial proliferation, impairs Closure 5 formation and delays PNP closure. After closure, the distal NT of Fgfr1-disrupted embryos dilates to form a fluid-filled sac overlying ventrally flattened spinal cord. This phenotype resembles terminal myelocystocele. Histological analysis reveals regional and progressive loss of SHH- and FOXA2-positive ventral NT domains, resulting in OLIG2 labelling of the ventral-most NT. The OLIG2 domain is also subsequently lost, eventually producing a NT that is entirely positive for the dorsal marker PAX3. Thus, a terminal myelocystocele-like phenotype can arise after completion of NT closure with localised spinal mis-patterning caused by disruption of FGFR1 signalling.

Omega-3 polygenic score protects against altered eating behavior in intrauterine growth-restricted children

BACKGROUND

Alterations in eating behavior are common in infants with intrauterine growth restriction (IUGR); omega-3 polyunsaturated fatty acids (PUFA) could provide protection. We hypothesized that those born IUGR with a genetic background associated with increased production of omega-3-PUFA will have more adaptive eating behaviors during childhood.

METHODS

IUGR/non-IUGR classified infants from MAVAN and GUSTO cohorts were included at the age of 4 and 5 years, respectively. Their parents reported child's eating behaviors using the child eating behavior questionnaire-CEBQ. Based on the GWAS on serum PUFA (Coltell 2020), three polygenic scores were calculated.

RESULTS

Significant interactions between IUGR and polygenic score for omega-3-PUFA on emotional overeating (β = -0.15, P = 0.049 GUSTO) and between IUGR and polygenic score for omega-6/omega-3-PUFA on desire to drink (β = 0.35, P = 0.044 MAVAN), pro-intake/anti-intake ratio (β = 0.10, P = 0.042 MAVAN), and emotional overeating (β = 0.16, P = 0.043 GUSTO) were found. Only in IUGR, a higher polygenic score for omega-3-PUFA associated with lower emotional overeating, while a higher polygenic score for omega-6/omega-3-PUFA ratio was associated with a higher desire to drink, emotional overeating, and pro-intake/anti-intake.

CONCLUSION

Only in IUGR, the genetic background for higher omega-3-PUFA is associated with protection against altered eating behavior, while the genetic score for a higher omega-6/omega-3-PUFA ratio is associated with altered eating behavior.

IMPACT

A genetic background related to a higher polygenic score for omega-3 PUFA protected infants born IUGR against eating behavior alterations, while a higher polygenic score for omega-6/omega-3 PUFA ratio increased the risk of having eating behavior alterations only in infants born IUGR, irrespective of their adiposity in childhood. Genetic individual differences modify the effect of being born IUGR on eating outcomes, increasing the vulnerability/resilience to eating disorders in IUGR group and likely contributing to their risk for developing metabolic diseases later in life.

CIC missense variants contribute to susceptibility for spina bifida

Neural tube defects (NTDs) are congenital malformations resulting from abnormal embryonic development of the brain, spine, or spinal column. The genetic etiology of human NTDs remains poorly understood despite intensive investigation. CIC, homolog of the Capicua transcription repressor, has been reported to interact with ataxin-1 (ATXN1) and participate in the pathogenesis of spinocerebellar ataxia type 1. Our previous study demonstrated that CIC loss of function (LoF) variants contributed to the cerebral folate deficiency syndrome by downregulating folate receptor 1 (FOLR1) expression. Given the importance of folate transport in neural tube formation, we hypothesized that CIC variants could contribute to increased risk for NTDs by depressing embryonic folate concentrations. In this study, we examined CIC variants from whole-genome sequencing (WGS) data of 140 isolated spina bifida cases and identified eight missense variants of CIC gene. We tested the pathogenicity of the observed variants through multiple in vitro experiments. We determined that CIC variants decreased the FOLR1 protein level and planar cell polarity (PCP) pathway signaling in a human cell line (HeLa). In a murine cell line (NIH3T3), CIC loss of function variants downregulated PCP signaling. Taken together, this study provides evidence supporting CIC as a risk gene for human NTD.

A case report of melanotic neuroectodermal tumor of infancy complicated with congenital heart disease and hypothyroidism

To the best of our knowledge, thus far there are no reported cases of melanotic neuroectodermal tumor of infancy (MNTI) with multiple complications. In this case report, we describe the clinical phenotype of MNTI in a 9-month-old female infant associated with tetralogy of Fallot (TOF), a congenital heart defect, and congenital hypothyroidism (CH). Our study showed that the growth of MNTI was delayed by a lower dosage of levothyroxine (L-T4) that was prescribed to treat CH because of the presence of TOF, a severe congenital heart disease. However, the standardized dosage of L-T4 improved thyroid function but stimulated the rapid growth of MNTI. Our report demonstrated that treatment with L-T4 affects the progression of MNTI. Our findings demonstrated the role of thyroid hormone in MNTI growth and progression. Furthermore, our study suggested that the treatment of co-morbidities in children with MNTI requires careful consideration of their effects on the growth and progression of MNTI.

Pax3/7 regulates neural tube closure and patterning in a non-vertebrate chordate

Pax3/7 factors play numerous roles in the development of the dorsal nervous system of vertebrates. From specifying neural crest at the neural plate borders, to regulating neural tube closure and patterning of the resulting neural tube. However, it is unclear which of these roles are conserved in non-vertebrate chordates. Here we investigate the expression and function of Pax3/7 in the model tunicate Ciona. Pax3/7 is expressed in neural plate border cells during neurulation, and in central nervous system progenitors shortly after neural tube closure. We find that separate cis-regulatory elements control the expression in these two distinct lineages. Using CRISPR/Cas9-mediated mutagenesis, we knocked out Pax3/7 in F0 embryos specifically in these two separate territories. Pax3/7 knockout in the neural plate borders resulted in neural tube closure defects, suggesting an ancient role for Pax3/7 in this chordate-specific process. Furthermore, knocking out Pax3/7 in the neural impaired Motor Ganglion neuron specification, confirming a conserved role for this gene in patterning the neural tube as well. Taken together, these results suggests that key functions of Pax3/7 in neural tube development are evolutionarily ancient, dating back at least to the last common ancestor of vertebrates and tunicates.

Pathogenesis of neural tube defects: The regulation and disruption of cellular processes underlying neural tube closure

Neural tube closure (NTC) is crucial for proper development of the brain and spinal cord and requires precise morphogenesis from a sheet of cells to an intact three-dimensional structure. NTC is dependent on successful regulation of hundreds of genes, a myriad of signaling pathways, concentration gradients, and is influenced by epigenetic and environmental cues. Failure of NTC is termed a neural tube defect (NTD) and is a leading class of congenital defects in the United States and worldwide. Though NTDs are all defined as incomplete closure of the neural tube, the pathogenesis of an NTD determines the type, severity, positioning, and accompanying phenotypes. In this review, we survey pathogenesis of NTDs relating to disruption of cellular processes arising from genetic mutations, altered epigenetic regulation, and environmental influences by micronutrients and maternal condition. This article is categorized under: Congenital Diseases > Genetics/Genomics/Epigenetics Neurological Diseases > Genetics/Genomics/Epigenetics Neurological Diseases > Stem Cells and Development.

Tripeptide Leu-Pro-Phe from Corn Protein Hydrolysates Attenuates Hyperglycemia-Induced Neural Tube Defect in Chicken Embryos

Neural tube defect (NTD) is the most common and severe embryopathy causing embryonic malformation and even death associated with gestational diabetes mellitus (GDM). Leu-Pro-Phe (LPF) is an antioxidative tripeptide isolated from hydrolysates of corn protein. However, the biological activity of LPF in vivo and in vitro remains unclear. This study is aimed at investigating the protective effects of tripeptide LPF against NTD in the high glucose exposure condition and delineate the underlying biological mechanism. We found that LPF alleviated NTD in the high glucose-exposed chicken embryo model. In addition, DF-1 chicken embryo fibroblast was loaded with high glucose for induction of oxidative stress and abnormal O-GlcNAcylation in vitro. LPF significantly decreased accumulation of reactive oxygen species and content of malondialdehyde in DF-1 cells but increased the ratio of reduced glutathione and oxidized glutathione in chick embryo. Oxygen radical absorbance capacity results showed that LPF itself had good free radical scavenging capacity and could enhance antioxidant activity of the cell content. Mechanistic studies suggested that the resistance of LPF to oxidative damage may be related to promotion of NRF2 expression and nuclear translocation. LPF alleviated the overall O-GlcNAcylation level of cellular proteins under high glucose conditions and restored the level of Pax3 protein. Collectively, our findings indicate that LPF peptide could act as a nutritional supplement for the protection of development of embryonic neural tube affected by GDM.

Spina Bifida: A Review of the Genetics, Pathophysiology and Emerging Cellular Therapies

Spina bifida is the most common congenital defect of the central nervous system which can portend lifelong disability to those afflicted. While the complete underpinnings of this disease are yet to be fully understood, there have been great advances in the genetic and molecular underpinnings of this disease. Moreover, the treatment for spina bifida has made great advancements, from surgical closure of the defect after birth to the now state-of-the-art intrauterine repair. This review will touch upon the genetics, embryology, and pathophysiology and conclude with a discussion on current therapy, as well as the first FDA-approved clinical trial utilizing stem cells as treatment for spina bifida.

Overview of Neural Tube Defects: Gene–Environment Interactions, Preventative Approaches and Future Perspectives

Neural tube defects (NTDs) are the second most common congenital malformations of humans, characterized by impaired development of the central nervous system. Even though the etiology of most birth defects remains undetermined, genetic and environmental risk factors in the background of NTDs have been identified and extensively reported. On top of genetic and nutritional risks which include mutations in both coding and non-coding regions and maternal folate status, respectively, recent years have seen a rise in the identification of a variety of teratogens that could be implicated in NTD development. These include polycyclic aromatic hydrocarbons, arsenic, pesticides, maternal hyperthermia and antibiotics as well as pain and seizure medication. With an increase in understanding of teratogens leading to NTD formation, preventative and treatment approaches have witnessed great advances throughout the years. While the most common preventative approach includes folic acid food fortification as well as suggested inositol supplementation, treatment and management approaches differ greatly depending on the developmental stage and the site of the lesion and include prenatal surgery, stem cell transplantation and postnatal surgery. Because NTDs still represent a large health and financial burden for the patient and society as a whole, it is crucial to investigate potential risk factors and develop novel approaches in order to fully prevent this category of disorders.

Micronutrient imbalance and common phenotypes in neural tube defects

Neural tube defects (NTDs) are among the most common birth defects, with a prevalence of close to 19 per 10,000 births worldwide. The etiology of NTDs is complex involving the interplay of genetic and environmental factors. Since nutrient deficiency is a risk factor and dietary changes are the major preventative measure to reduce the risk of NTDs, a more detailed understanding of how common micronutrient imbalances contribute to NTDs is crucial. While folic acid has been the most discussed environmental factor due to the success that population-wide fortification has had on prevention of NTDs, folic acid supplementation does not prevent all NTDs. The imbalance of several other micronutrients has been implicated as risks for NTDs by epidemiological studies and in vivo studies in animal models. In this review, we highlight recent literature deciphering the multifactorial mechanisms underlying NTDs with an emphasis on mouse and human data. Specifically, we focus on advances in our understanding of how too much or too little retinoic acid, zinc, and iron alter gene expression and cellular processes contributing to the pathobiology of NTDs. Synthesis of the discussed literature reveals common cellular phenotypes found in embryos with NTDs resulting from several micronutrient imbalances. The goal is to combine knowledge of these common cellular phenotypes with mechanisms underlying micronutrient imbalances to provide insights into possible new targets for preventative measures against NTDs.

Genetic interaction of Pax3 mutation and canonical Wnt signaling modulates neural tube defects and neural crest abnormalities

Mouse models provide opportunities to investigate genetic interactions that cause or modify the frequency of neural tube defects (NTDs). Mutation of the PAX3 transcription factor prevents neural tube closure, leading to cranial and spinal NTDs whose frequency is responsive to folate status. Canonical Wnt signalling is implicated both in regulation of Pax3 expression and as a target of PAX3. This study investigated potential interactions of Pax3 mutation and canonical Wnt signalling using conditional gain- and loss-of-function models of β-catenin. We found an additive effect of β-catenin gain of function and Pax3 loss of function on NTDs and neural crest defects. β-catenin gain of function in the Pax3 expression domain led to significantly increased frequency of cranial but not spinal NTDs in embryos that are heterozygous for Pax3 mutation, while both cranial and spinal neural tube closure were exacerbated in Pax3 homozygotes. Similarly, deficits of migrating neural crest cells were exacerbated by β-catenin gain of function, with almost complete ablation of spinal neural crest cells and derivatives in Pax3 homozygous mutants. Pax3 expression was not affected by β-catenin gain of function, while we confirmed that loss of function led to reduced Pax3 transcription. In contrast to gain of function, β-catenin knockout in the Pax3 expression domain lowered the frequency of cranial NTDs in Pax3 null embryos. However, loss of function of β-catenin and Pax3 resulted in spinal NTDs, suggesting differential regulation of cranial and spinal neural tube closure. In summary, β-catenin function modulates the frequency of PAX3-related NTDs in the mouse.

Transcription factors in neurodevelopmental and associated psychiatric disorders: A potential convergence for genetic and environmental risk factors

Neurodevelopmental disorders (NDDs) are a heterogeneous and highly prevalent group of psychiatric conditions marked by impairments in the nervous system. Their onset occurs during gestation, and the alterations are observed throughout the postnatal life. Although many genetic and environmental risk factors have been described in this context, the interactions between them challenge the understanding of the pathways associated with NDDs. Transcription factors (TFs)-a group of over 1,600 proteins that can interact with DNA, regulating gene expression through modulation of RNA synthesis-represent a point of convergence for different risk factors. In addition, TFs organize critical processes like angiogenesis, blood-brain barrier formation, myelination, neuronal migration, immune activation, and many others in a time and location-dependent way. In this review, we summarize important TF alterations in NDD and associated disorders, along with specific impairments observed in animal models, and, finally, establish hypotheses to explain how these proteins may be critical mediators in the context of genome-environment interactions.

Stem Cell Neurodevelopmental Solutions for Restorative Treatments of the Human Trunk and Spine

The ability to reliably repair spinal cord injuries (SCI) will be one of the greatest human achievements realized in regenerative medicine. Until recently, the cellular path to this goal has been challenging. However, as detailed developmental principles are revealed in mouse and human models, their application in the stem cell community brings trunk and spine embryology into efforts to advance human regenerative medicine. New models of posterior embryo development identify neuromesodermal progenitors (NMPs) as a major bifurcation point in generating the spinal cord and somites and is leading to production of cell types with the full range of axial identities critical for repair of trunk and spine disorders. This is coupled with organoid technologies including assembloids, circuitoids, and gastruloids. We describe a paradigm for applying developmental principles towards the goal of cell-based restorative therapies to enable reproducible and effective near-term clinical interventions.

Deficient or Excess Folic Acid Supply During Pregnancy Alter Cortical Neurodevelopment in Mouse Offspring

Folate is an essential micronutrient required for both cellular proliferation through de novo nucleotide synthesis and epigenetic regulation of gene expression through methylation. This dual requirement places a particular demand on folate availability during pregnancy when both rapid cell generation and programmed differentiation of maternal, extraembryonic, and embryonic/fetal tissues are required. Accordingly, prenatal neurodevelopment is particularly susceptible to folate deficiency, which can predispose to neural tube defects, or when effective transport into the brain is impaired, cerebral folate deficiency. Consequently, adequate folate consumption, in the form of folic acid (FA) fortification and supplement use, is widely recommended and has led to a substantial increase in the amount of FA intake during pregnancy in some populations. Here, we show that either maternal folate deficiency or FA excess in mice results in disruptions in folate metabolism of the offspring, suggesting diversion of the folate cycle from methylation to DNA synthesis. Paradoxically, either intervention causes comparable neurodevelopmental changes by delaying prenatal cerebral cortical neurogenesis in favor of late-born neurons. These cytoarchitectural and biochemical alterations are accompanied by behavioral abnormalities in FA test groups compared with controls. Our findings point to overlooked potential neurodevelopmental risks associated with excessively high levels of prenatal FA intake.

Mechanisms of Congenital Malformations in Pregnancies with Pre-existing Diabetes

PURPOSE OF REVIEW

Fetuses of diabetic mothers are at increased risk for congenital malformations. Research in recent decades using animal and embryonic stem cell models has revealed many embryonic developmental processes that are disturbed by maternal diabetes. The aim of this review is to give clinicians a better understanding of the reasons for rigorous glycemic control in early pregnancy, and to provide background to guide future research.

RECENT FINDINGS

Mouse models of diabetic pregnancy have revealed mechanisms for altered expression of tissue-specific genes that lead to malformations that are more common in diabetic pregnancies, such as neural tube defects (NTDs) and congenital heart defects (CHDs), and how altered gene expression causes apoptosis that leads to malformations. Embryos express the glucose transporter, GLUT2, which confers susceptibility to malformation, due to high rates of glucose uptake during maternal hyperglycemia and subsequent oxidative stress; however, the teleological function of GLUT2 for mammalian embryos may be to transport the amino sugar glucosamine (GlcN) from maternal circulation to be used as substrate for glycosylation reactions and to promote embryo cell growth. Malformations in diabetic pregnancy may be not only due to excess glucose uptake but also due to insufficient GlcN uptake. Avoiding maternal hyperglycemia during early pregnancy should prevent excess glucose uptake via GLUT2 into embryo cells, and also permit sufficient GLUT2-mediated GlcN uptake.

The etiopathogenic and morphological spectrum of anencephaly: a comprehensive review of literature

Anencephaly is a severe malformation of the central nervous system (CNS), being one of the most common types of neural tube defects. It is defined as total or partial absence of the calvarium, with absence of the brain. Anencephaly has an incidence of 1 to 5 in every 1000 births, and the mortality rate is 100% during intrauterine life or within hours or days after birth. The etiology of anencephaly remains unclear, but various maternal-related environmental and genetic risk factors have been reported, which include diabetes, obesity, exposure to different drugs or toxins, genetic polymorphisms and mutations, as well as positive family history for neural tube defects. One of the most important nutritional factors in the development of anencephaly is folate deficiency. Methylenetetrahydrofolate reductase (MTHFR) gene codes the enzyme involved in the intracellular metabolism of folic acid; the 677C-T polymorphism of this gene causes the thermolability of the enzyme and decreased enzymatic activity, which is also dependent of folate plasmatic level. Etiopathogenesis of anencephaly includes several mutations in various other genes, such as: platelet-derived growth factor receptor alpha (PDGFRA), cadherin epidermal growth factor (EGF) laminin G (LAG) seven-pass G-type receptor 1 (CELSR1), Vang-like 1 (VANGL1) and Vang-like 2 (VANGL2), the last two being involved in the process of neurulation. Screening tests include maternal serum alpha-fetoprotein level and ultrasound (US) examination. During the first trimester US screening, anencephaly is now detected in all cases, but in order to decrease the complication rate of pregnancy termination, the diagnosis should be established as soon as possible, during the pregnancy confirmation US. We conclude that given that anencephaly is a severe malformation of the CNS, morphological characterization could improve the screening by US that is mandatory in the first trimester in order to plan the best, safe and early management.