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.

Aberrant Gcm1 expression mediates Wnt/ß-catenin pathway activation in folate deficiency involved in neural tube defects.

Wnt signaling plays a major role in early neural development. An aberrant activation in Wnt/ß-catenin pathway causes defective anteroposterior patterning, which results in neural tube closure defects (NTDs). Changes in folate metabolism may participate in early embryo fate determination. We have identified that folate deficiency activated Wnt/ß-catenin pathway by upregulating a chorion-specific transcription factor Gcm1. Specifically, folate deficiency promoted formation of the Gcm1/ß-catenin/T-cell factor (TCF4) complex formation to regulate the Wnt targeted gene transactivation through Wnt-responsive elements. Moreover, the transcription factor Nanog upregulated Gcm1 transcription in mESCs under folate deficiency. Lastly, in NTDs mouse models and low-folate NTDs human brain samples, Gcm1 and Wnt/ß-catenin targeted genes related to neural tube closure are specifically overexpressed. These results indicated that low-folate level promoted Wnt/ß-catenin signaling via activating Gcm1, and thus leaded into aberrant vertebrate neural development.

Tendencia de los Defectos de Tubo Neural en el Estado de Hidalgo México del 2013-2018 / Trend of Neural Tube Defects in Hidalgo Mexico from 2013-2018

INTRODUCCIÓN: los Defectos de Tubo Neural (DTN) son defectos congénitos del sistema nervioso central resultado del cierre inadecuado en alguna zona del tubo neural, siendo los más frecuentes Anencefalia y Espina Bífida en sus diferentes variantes. En Latinoamérica y México se encuentran dentro de las principales causas de morbilidad y mortalidad infantil. MATERIAL Y MÉTODOS: Análisis de series de tiempo de casos y defunciones de DTN en Hidalgo del 2013-2018 generado a partir de la base de datos de la Dirección General de Vigilancia Epidemiológica de los Defectos del Tubo Neural y Craneofaciales proporcionada por la Secretaria de Salud del Estado de Hidalgo, se incluyeron 187 casos con DTN que nacieron y radican en el Estado. Se calcularon las tasas de mortalidad infantil específicas por DTN con el objetivo de identificar probables factores que incidan o incrementen dichas tendencias. RESULTADOS: la incidencia de DTN fue de 58.7 en el periodo estudiado, la Anencefalia es el más incidente 45% (84), seguido del Mielomeningocele 33% (62) él cual muestra una incidencia creciente. El 84% de la población estaba afiliada al Seguro Popular. Solo el 7.5% (14) de las madres de los casos consumieron ácido fólico tres meses previos al embarazo y el 55% (103) acudieron a 3 consultas prenatales o menos. CONCLUSIONES: Los DTN requieren de estudio y vigilancia permanente pues representan una causa importante de morbilidad y mortalidad en la infancia que afecta a los individuos que los padecen, sus familias, la sociedad y el sistema de salud, con esto se evitarían resultados negativos

INTRODUCTION: Neural Tube Defects (DTN) are congenital defects of the central nervous system resulting from an inadequate closure in some area of ​​the neural tube, the most frequent being Anencephaly and Spina Bifida in their different variants. In Latin America and Mexico, they are among the main causes of infant morbidity and mortality. MATERIAL AND METHODS: Analysis of time series of cases and deaths of DTN in Hidalgo from 2013-2018 generated from the database of the General Directorate of Epidemiological Surveillance of Neural Tube and Craniofacial Defects directly by the Ministry of Health of the State of Hidalgo, included 187 cases with DTN that were born and reside in the State. DTN specific infant mortality rates will be calculated in order to identify probable factors that influence or increase various trends. RESULTS: the incidence of DTN was 58.7 in the period studied, Anencephaly is the most incident 45% (84), followed by Myelomeningocele 33% (62), which shows an increasing incidence. 84% of the population was affiliated at the Seguro Popular. Only 7.5% (14) of the mothers of the cases consumed folic acid three months before the pregnancy and 55% (103) attended 3 or less prenatal visits. CONCLUSIONS: DTN are problems of study and permanent surveillance, since they represent an important cause of morbidity and mortality in childhood that affect the individuals who suffer, their families, society and the health system, this would avoid negative results

Hidrocefalia infantil en el África subsahariana: impacto de los cuidados perioperatorios en el archipiélago de Zanzíbar / Infant hydrocephalus in sub-Saharan Africa: Impact of perioperative care in the Zanzibar archipelago

INTRODUCCIÓN: La hidrocefalia infantil en países de bajo y mediano ingreso, representa uno de los problemas éticos y sanitarios más conflictivos con los que se enfrenta el desarrollo de la salud a nivel internacional. Las estimaciones más optimistas señalan que 200.000 nacidos anualmente desarrollarán una hidrocefalia o nacerán con un defecto del tubo neural en África oriental, central y sur de África (ECSA). Se calcula que menos del 10% de estos niños serán operados mediante derivaciones ventriculoperitoneales y, en general, en condiciones de mala calidad o con un índice de complicaciones muy elevado. OBJETIVO: Describir las características generales, la epidemiología y los datos demográficos de la hidrocefalia infantil de los pacientes atendidos en el Instituto NED en el archipiélago de Zanzíbar y valorar los detalles clínicos y los resultados a medio plazo del impacto de los cuidados de enfermería implantados. MATERIAL Y MÉTODOS: Se trata de un estudio observacional descriptivo y analítico de carácter retrospectivo, en pacientes diagnosticados y tratados de hidrocefalia infantil, en el período comprendido entre septiembre del 2016 y septiembre del 2018. Con la implantación de una serie de protocolos perioperatorios de enfermería en dichos pacientes, se describieron y analizaron los resultados obtenidos. RESULTADOS: Un total de 96 pacientes fueron atendidos de hidrocefalia infantil. Un 51% (n = 49) de estos pacientes eran varones, con una media de edad de 9,25 meses. Todas las madres de los pacientes fueron controladas durante el embarazo, pero solamente un 8% de ellas fueron tratadas con ácido fólico durante su gestación. El 81% de los niños nacieron mediante parto vaginal o parto espontáneo no complicado. Con respecto a la etiología, el 27,1% de la hidrocefalia tratada estaba asociada a una causa infecciosa y un 35,4% a una causa desconocida. Se realizaron 67 cirugías de derivación ventriculoperitoneal y 15 ventriculostomías endoscópicas. La tasa de complicaciones fue del 23,17%. CONCLUSIONES: Los resultados de esta investigación indican que la hidrocefalia infantil en Zanzíbar tiene una etiología, una evolución y unas complicaciones similares o menores que las descritas hasta la fecha en el África oriental. El hecho de implantar una serie de protocolos perioperatorios y cuidados estandarizados de enfermería influyen positivamente en los resultados obtenidos. En la actualidad, el Mnazi Mmoja Surgical NED Institute es uno de los escasos centros en África del Este con un registro exhaustivo de la actividad asistencial y el primer centro sanitario que oferta una formación continuada al personal de enfermería

INTRODUCTION: Child hydrocephalus in low- and middle-income countries represents one of the most sensitive ethical and health problems facing international health development. The most optimistic estimates indicate that 200,000 newborns annually will develop hydrocephalus or be born with a neural tube defect in East, Central and South Africa (ECSA). It is estimated that less than 10% of these children will be operated by ventriculoperitoneal shunts, and in general in poor quality conditions or with a very high complication rate. OBJECTIVE: To describe the general characteristics, epidemiology and demographic data of childhood hydrocephalus of patients treated at the NED Institute in the Zanzibar archipelago, and assess the clinical details and medium-term results of the impact of the set-up nursing care. MATERIAL AND METHODS: This is a descriptive and analytical observational study of a retrospective nature, in patients diagnosed and treated with childhood hydrocephalus, in the period from September 2016 to September 2018. With the implementation of a series of perioperative nursing protocols in these patients, the results obtained were described and analyzed. RESULTS: A total of 96 patients were treated for childhood hydrocephalus. 51% (n = 49) of these patients were male, with a mean age of 9.25 months. All the mothers of the patients were monitored during pregnancy, but only 8% were treated with folic acid during pregnancy. 81% of children were born through vaginal delivery or uncomplicated spontaneous delivery. Regarding the etiology, 27.1% of treated hydrocephalus was associated with an infectious cause and 35.4% with an unknown cause. 67 ventriculoperitoneal shunt surgery and 15 endoscopic ventriculostomies were performed. The complication rate was 23.17%. CONCLUSIONS: The results of this research indicate that childhood hydrocephalus in Zanzibar has etiology, evolution and complications that are similar to or less than those described to date in East Africa. Implementing a series of perioperative protocols and standardized nursing care positively influences the results obtained. Currently, the Mnazi Mmoja Surgical NED Institute is one of the few centers in East Africa with an exhaustive record of healthcare activity and is the first health center that offers further training to nurses

Somatic mutations in planar cell polarity genes in neural tissue from human fetuses with neural tube defects.

Extensive studies that have sought causative mutation(s) for neural tube defects (NTDs) have yielded limited positive findings to date. One possible reason for this is that many studies have been confined to analyses of germline mutations and so may have missed other, non-germline mutations in NTD cases. We hypothesize that somatic mutations of planar polarity pathway (PCP) genes may play a role in the development of NTDs. Torrent™ Personal Genome Machine™ (PGM) sequencing was designed for selected PCP genes in paired DNA samples extracted from the tissues of lesion sites and umbilical cord from 48 cases. Sanger sequencing was used to validate the detected mutations. The source and distribution of the validated mutations in tissues from different germ layers were investigated. Subcellular location, western blotting, and luciferase assays were performed to better understand the effects of the mutations on protein localization, protein level, and pathway signaling. ix somatic mutations were identified and validated, which showed diverse distributions in different tissues. Three somatic mutations were novel/rare: CELSR1 p.Gln2125His, FZD6 p.Gln88Glu, and VANGL1 p.Arg374His. FZD6 p.Gln88Glu caused mislocalization of its protein from the cytoplasm to the nucleus, and disrupted the colocalization of CELSR1 and FZD6. This mutation affected non-canonical WNT signaling in luciferase assays. VANGL1 p.Arg374His impaired the co-localization of CELSR1 and VANGL1, increased the protein levels of VANGL1, and influenced cell migration. In all, 7/48 (14.5%) of the studied NTD cases contained somatic PCP mutations. Somatic mutations in PCP genes (e.g., FZD6 and VANGL1) are associated with human NTDs, and they may occur in different stages and regions during embryonic development, resulting in a varied distribution in fetal tissues/organs.

Non-neural surface ectodermal rosette formation and F-actin dynamics drive mammalian neural tube closure.

The mechanisms underlying mammalian neural tube closure remain poorly understood. We report a unique cellular process involving multicellular rosette formation, convergent cellular protrusions, and F-actin cable network of the non-neural surface ectodermal cells encircling the closure site of the posterior neuropore, which are demonstrated by scanning electron microscopy and genetic fate mapping analyses during mouse spinal neurulation. These unique cellular structures are severely disrupted in the surface ectodermal transcription factor Grhl3 mutants that exhibit fully penetrant spina bifida. We propose a novel model of mammalian neural tube closure driven by surface ectodermal dynamics, which is computationally visualized.

Siva plays a critical role in mouse embryonic development.

The Siva protein, named after the Hindu God of Destruction, plays important roles in apoptosis in various contexts, including downstream of death receptor activation or p53 tumor suppressor engagement. The function of Siva in organismal development and homeostasis, however, has remained uncharacterized. Here, we generate Siva knockout mice to characterize the physiological function of Siva in vivo. Interestingly, we find that Siva deficiency causes early embryonic lethality accompanied by multiple phenotypes, including developmental delay, abnormal neural tube closure, and defective placenta and yolk sac formation. Examination of Siva expression during embryogenesis shows that Siva is expressed in both embryonic and extra-embryonic tissues, including within the mesoderm, which may explain the vascular defects observed in the placenta and yolk sac. The embryonic phenotypes caused by Siva loss are not rescued by p53 deficiency, nor do they resemble those of p53 null embryos, suggesting that the embryonic function of Siva is not related to the p53 pathway. Moreover, loss of the Ripk3 necroptosis protein does not rescue the observed lethality or developmental defects, suggesting that Siva may play a non-apoptotic role in development. Collectively, these studies reveal a key role for Siva in proper embryonic development.

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)

Derepression of sonic hedgehog signaling upon Gpr161 deletion unravels forebrain and ventricular abnormalities.

Inverse gradients of transcriptional repressors antagonize the transcriptional effector response to morphogens. However, the role of such inverse regulation might not manifest solely from lack of repressors. Sonic hedgehog (Shh) patterns the forebrain by being expressed ventrally; however, absence of antagonizing Gli3 repressor paradoxically cause insufficient pathway activation. Interestingly, lack of the primary cilia-localized G-protein-coupled receptor, Gpr161 increases Shh signaling in the mouse neural tube from coordinated lack of Gli3 repressor and Smoothened-independent activation. Here, by deleting Gpr161 in mouse neuroepithelial cells and radial glia at early mid-gestation we detected derepression of Shh signaling throughout forebrain, allowing determination of the pathophysiological consequences. Accumulation of cerebrospinal fluid (hydrocephalus) was apparent by birth, although usual causative defects in multiciliated ependymal cells or aqueduct were not seen. Rather, the ventricular surface was expanded (ventriculomegaly) during embryogenesis from radial glial overproliferation. Cortical phenotypes included polymicrogyria in the medial cingulate cortex, increased proliferation of intermediate progenitors and basal radial glia, and altered neocortical cytoarchitectonic structure with increased upper layer and decreased deep layer neurons. Finally, periventricular nodular heterotopia resulted from disrupted neuronal migration, while the radial glial scaffold was unaffected. Overall, suppression of Shh pathway during early mid-gestation prevents ventricular overgrowth, and regulates cortical gyration and neocortical/periventricular cytoarchitecture.

Zinc deficiency causes neural tube defects through attenuation of p53 ubiquitylation.

Micronutrition is essential for neural tube closure, and zinc deficiency is associated with human neural tube defects. Here, we modeled zinc deficiency in mouse embryos, and used live imaging and molecular studies to determine how zinc deficiency affects neural tube closure. Embryos cultured with the zinc chelator TPEN failed to close the neural tube and showed excess apoptosis. TPEN-induced p53 protein stabilization in vivo and in neuroepithelial cell cultures and apoptosis was dependent on p53. Mechanistically, zinc deficiency resulted in disrupted interaction between p53 and the zinc-dependent E3 ubiquitin ligase Mdm2, and greatly reduced p53 ubiquitylation. Overexpression of human CHIP, a zinc-independent E3 ubiquitin ligase that targets p53, relieved TPEN-induced p53 stabilization and reduced apoptosis. Expression of p53 pro-apoptotic target genes was upregulated by zinc deficiency. Correspondingly, embryos cultured with p53 transcriptional activity inhibitor pifithrin-α could overcome TPEN-induced apoptosis and failure of neural tube closure. Our studies indicate that zinc deficiency disrupts neural tube closure through decreased p53 ubiquitylation, increased p53 stabilization and excess apoptosis.

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.

Protein kinase C-alpha suppresses autophagy and induces neural tube defects via miR-129-2 in diabetic pregnancy.

Gene deletion-induced autophagy deficiency leads to neural tube defects (NTDs), similar to those in diabetic pregnancy. Here we report the key autophagy regulators modulated by diabetes in the murine developing neuroepithelium. Diabetes predominantly leads to exencephaly, induces neuroepithelial cell apoptosis and suppresses autophagy in the forebrain and midbrain of NTD embryos. Deleting the Prkca gene, which encodes PKCα, reverses diabetes-induced autophagy impairment, cellular organelle stress and apoptosis, leading to an NTD reduction. PKCα increases the expression of miR-129-2, which is a negative regulator of autophagy. miR-129-2 represses autophagy by directly targeting PGC-1α, a positive regulator for mitochondrial function, which is disturbed by maternal diabetes. PGC-1α supports neurulation by stimulating autophagy in neuroepithelial cells. These findings identify two negative autophagy regulators, PKCα and miR-129-2, which mediate the teratogenicity of hyperglycaemia leading to NTDs. We also reveal a function for PGC-1α in embryonic development through promoting autophagy and ameliorating hyperglycaemia-induced NTDs.

Cirugía precoz en la prevención de la sepsis del recién nacido con mielomeningocele / Precocious surgery in preventing the sepsis of newborn with meningomyelocele

El mielomeningocele es una malformación congénita por defecto del cierre del tubo neural, se produce en las primeras semanas de crecimiento intrauterino. Consiste en una masa quística que incluye tejido nervioso y meninges, acompañadas de una fusión incompleta de los arcos vertebrales. Produce severos daños neurales y puede asociarse a otras malformaciones. Su reparación, en las primeras horas de vida, es necesaria para evitar complicaciones que pueden comprometer la vida del niño o causar mayor discapacidad. Se reportó un caso de un recién nacido con diagnóstico de mielomeningocele fisurado, a nivel lumbar. Se intervino quirúrgicamente en las primeras 6 h de vida; se disecó el saco dural y se separaron las raíces, logrando el cierre completo de la duramadre. Se reparó la piel con afrontamiento de los bordes y adecuada cicatrización de la herida. Fue aplicada antibioticoterapia profiláctica con cefalosporina de tercera generación. El infante egresó a los 10 días de operado sin complicaciones neuroquirúgicas asociadas (AU).

Meningomyelocele is a congenital malformation by defect of neural tube closing, produced in the first weeks of intrauterine grow. It is a cystic mass that includes nervous tissues and meninges, together with an incomplete fusion of the vertebral arches. It produces severe neural damages and could be associated to other malformations. It is necessary to repair it during the first hours after birth to avoid complications that could compromise the childs life or cause more disability. The case of a new-born child diagnosed with fissured meningomyelocele at the lumbar level is presented. He was operated in the first six hours after birth; the dural sac was dissected and the roots separated, reaching the complete dura mater closure. The skin was repaired with edges affronting and adequate wound healing. Prophylactic antibiotic therapy with third generation cephalosporin was applied. The child was discharged 10 days alter the surgery without associated neurosurgical complications (AU).

Cirugía precoz en la prevención de la sepsis del recién nacido con mielomeningocele / Precocious surgery in preventing the sepsis of newborn with meningomyelocele

El mielomeningocele es una malformación congénita por defecto del cierre del tubo neural, se produce en las primeras semanas de crecimiento intrauterino. Consiste en una masa quística que incluye tejido nervioso y meninges, acompañadas de una fusión incompleta de los arcos vertebrales. Produce severos daños neurales y puede asociarse a otras malformaciones. Su reparación, en las primeras horas de vida, es necesaria para evitar complicaciones que pueden comprometer la vida del niño o causar mayor discapacidad. Se reportó un caso de un recién nacido con diagnóstico de mielomeningocele fisurado, a nivel lumbar. Se intervino quirúrgicamente en las primeras 6 h de vida; se disecó el saco dural y se separaron las raíces, logrando el cierre completo de la duramadre. Se reparó la piel con afrontamiento de los bordes y adecuada cicatrización de la herida. Fue aplicada antibioticoterapia profiláctica con cefalosporina de tercera generación. El infante egresó a los 10 días de operado sin complicaciones neuroquirúgicas asociadas (AU).

Meningomyelocele is a congenital malformation by defect of neural tube closing, produced in the first weeks of intrauterine grow. It is a cystic mass that includes nervous tissues and meninges, together with an incomplete fusion of the vertebral arches. It produces severe neural damages and could be associated to other malformations. It is necessary to repair it during the first hours after birth to avoid complications that could compromise the child’s life or cause more disability. The case of a new-born child diagnosed with fissured meningomyelocele at the lumbar level is presented. He was operated in the first six hours after birth; the dural sac was dissected and the roots separated, reaching the complete dura mater closure. The skin was repaired with edges affronting and adequate wound healing. Prophylactic antibiotic therapy with third generation cephalosporin was applied. The child was discharged 10 days alter the surgery without associated neurosurgical complications (AU).

Neural tube closure and embryonic metabolism.

Neural tube closure (NTC) is an embryonic process during formation of the mammalian central nervous system. Disruption of the dynamic, sequential events of NTC can cause neural tube defects (NTD) leading to spina bifida and anencephaly in the newborn. NTC is affected by inherent factors such as genetic mutation or if the mother is exposed to certain environmental factors such as intake of harmful chemicals, maternal infection, irradiation, malnutrition, and inadequate or excessive intake of specific nutrients. Although effects of these stress factors on NTC have been intensively studied, the metabolic state of a normally developing embryo remains unclear. State-of-the art mass spectrometry techniques have enabled detailed study of embryonic metabolite profiles and their distribution within tissues. This approach has demonstrated that glucose metabolism is altered during NTC stages involving chorioallantoic branching. An understanding of embryonic metabolic rewiring would help reveal the etiology of NTD caused by environmental factors.

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.

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.

Mechanics of neurulation: From classical to current perspectives on the physical mechanics that shape, fold, and form the neural tube.

Neural tube defects arise from mechanical failures in the process of neurulation. At the most fundamental level, formation of the neural tube relies on coordinated, complex tissue movements that mechanically transform the flat neural epithelium into a lumenized epithelial tube (Davidson, 2012). The nature of this mechanical transformation has mystified embryologists, geneticists, and clinicians for more than 100 years. Early embryologists pondered the physical mechanisms that guide this transformation. Detailed observations of cell and tissue movements as well as experimental embryological manipulations allowed researchers to generate and test elementary hypotheses of the intrinsic and extrinsic forces acting on the neural tissue. Current research has turned toward understanding the molecular mechanisms underlying neurulation. Genetic and molecular perturbation have identified a multitude of subcellular components that correlate with cell behaviors and tissue movements during neural tube formation. In this review, we focus on methods and conceptual frameworks that have been applied to the study of amphibian neurulation that can be used to determine how molecular and physical mechanisms are integrated and responsible for neurulation. We will describe how qualitative descriptions and quantitative measurements of strain, force generation, and tissue material properties as well as simulations can be used to understand how embryos use morphogenetic programs to drive neurulation. Birth Defects Research 109:153-168, 2017. © 2016 Wiley Periodicals, Inc.

Inositol, neural tube closure and the prevention of neural tube defects.

Susceptibility to neural tube defects (NTDs), such as anencephaly and spina bifida is influenced by genetic and environmental factors including maternal nutrition. Maternal periconceptional supplementation with folic acid significantly reduces the risk of an NTD-affected pregnancy, but does not prevent all NTDs, and "folic acid non-responsive" NTDs continue to occur. Similarly, among mouse models of NTDs, some are responsive to folic acid but others are not. Among nutritional factors, inositol deficiency causes cranial NTDs in mice while supplemental inositol prevents spinal and cranial NTDs in the curly tail (Grhl3 hypomorph) mouse, rodent models of hyperglycemia or induced diabetes, and in a folate-deficiency induced NTD model. NTDs also occur in mice lacking expression of certain inositol kinases. Inositol-containing phospholipids (phosphoinositides) and soluble inositol phosphates mediate a range of functions, including intracellular signaling, interaction with cytoskeletal proteins, and regulation of membrane identity in trafficking and cell division. Myo-inositol has been trialed in humans for a range of conditions and appears safe for use in human pregnancy. In pilot studies in Italy and the United Kingdom, women took inositol together with folic acid preconceptionally, after one or more previous NTD-affected pregnancies. In nonrandomized cohorts and a randomized double-blind study in the United Kingdom, no recurrent NTDs were observed among 52 pregnancies reported to date. Larger-scale fully powered trials are needed to determine whether supplementation with inositol and folic acid would more effectively prevent NTDs than folic acid alone. Birth Defects Research 109:68-80, 2017. © 2016 The Authors Birth Defects Research Published by Wiley Periodicals, Inc.