Perinatal outcomes of iatrogenic chorioamniotic separation following fetoscopic surgery: systematic review and meta-analysis

OBJECTIVE

To compare the perinatal outcomes between pregnancies with and those without iatrogenic chorioamniotic separation (iCAS) following fetoscopic intervention.

METHODS

We performed a search in PubMed, EMBASE, Scopus, Web of Science and Google Scholar from inception up to December 2020 for studies comparing perinatal outcomes between pregnancies that developed and those that did not develop iCAS after fetoscopic intervention for twin-to-twin transfusion syndrome (TTTS), open neural tube defect (ONTD) or congenital diaphragmatic hernia. A random-effects model was used to pool the mean differences (MD) or odds ratios (OR) and the corresponding 95% CI. The primary outcome was neonatal survival. Secondary outcomes included gestational age (GA) at intervention and at delivery, interval from intervention to delivery and incidence of preterm prelabor rupture of membranes (PPROM) and preterm delivery. The methodological quality of the included studies was evaluated using the Newcastle-Ottawa scale.

RESULTS

The search identified 348 records, of which seven studies (six on fetoscopic laser photocoagulation (FLP) for TTTS and one on fetoscopic repair for ONTD) assessed the perinatal outcomes of pregnancies that developed iCAS after fetoscopic intervention. Given that only one study reported on fetoscopic ONTD repair, the meta-analysis was limited to TTTS pregnancies and included six studies (total of 1881 pregnancies). Pregnancies that developed iCAS after FLP for TTTS, compared with those that did not, had significantly lower GA at the time of intervention (weeks) (MD, -1.07 (95% CI, -1.89 to -0.24); P = 0.01) and at delivery (weeks) (MD, -1.74 (95% CI, -3.13 to -0.34); P = 0.01) and significantly lower neonatal survival (OR, 0.41 (95% CI, 0.24-0.70); P = 0.001). In addition, development of iCAS after FLP for TTTS increased significantly the risk for PPROM < 34 weeks' gestation (OR, 3.98 (95% CI, 1.76-9.03); P < 0.001) and preterm delivery < 32 weeks (OR, 1.80 (95% CI, 1.16-2.80); P = 0.008).

CONCLUSIONS

iCAS is a common complication after FLP for TTTS. In patients undergoing FLP for TTTS, iCAS develops more often with earlier GA at intervention and is associated with earlier GA at delivery, higher risk of PPROM < 34 weeks' gestation and preterm delivery < 32 weeks and lower neonatal survival. Given the limitations of this meta-analysis and lack of literature reporting on other types of fetoscopic intervention, the presented findings should be interpreted with caution and should not be generalized to fetoscopic procedures used to treat other fetal conditions. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Okadaic Acid Exposure Induced Neural Tube Defects in Chicken (Gallus gallus) Embryos

Okadaic acid (OA) is an important liposoluble shellfish toxin distributed worldwide, and is mainly responsible for diarrheic shellfish poisoning in human beings. It has a variety of toxicities, including cytotoxicity, embryonic toxicity, neurotoxicity, and even genotoxicity. However, there is no direct evidence of its developmental toxicity in human offspring. In this study, using the chicken (Gallus gallus) embryo as the animal model, we investigated the effects of OA exposure on neurogenesis and the incidence of neural tube defects (NTDs). We found that OA exposure could cause NTDs and inhibit the neuronal differentiation. Immunofluorescent staining of pHI3 and c-Caspase3 demonstrated that OA exposure could promote cell proliferation and inhibit cell apoptosis on the developing neural tube. Besides, the down-regulation of Nrf2 and increase in reactive oxygen species (ROS) content and superoxide dismutase (SOD) activity in the OA-exposed chicken embryos indicated that OA could result in oxidative stress in early chick embryos, which might enhance the risk of the subsequent NTDs. The inhibition of bone morphogenetic protein 4 (BMP4) and Sonic hedgehog (Shh) expression in the dorsal neural tube suggested that OA could also affect the formation of dorsolateral hinge points, which might ultimately hinder the closure of the neural tube. Transcriptome and qPCR analysis showed the expression of lipopolysaccharide-binding protein (LBP), transcription factor AP-1 (JUN), proto-oncogene protein c-fos (FOS), and C-C motif chemokine 4 (CCL4) in the Toll-like receptor signaling pathway was significantly increased in the OA-exposed embryos, suggesting that the NTDs induced by OA might be associated with the Toll-like receptor signaling pathway. Taken together, our findings could advance the understanding of the embryo–fetal developmental toxicity of OA on human gestation.

Trend in ventricle size during pregnancy and its use for prediction of ventriculoperitoneal shunt in fetal open neural tube defect

OBJECTIVES

Fetal surgery for repair of open neural tube defect (ONTD) typically results in decreased need for a ventriculoperitoneal shunt (VPS). Our objectives were to determine the trend in ventricle size (VS) during pregnancy and whether VS and change in VS, as assessed by ultrasound, were predictive of the need for VPS in pregnancy with ONTD.

METHODS

This was a retrospective analysis of prospectively collected data of consecutive pregnancies with ONTD, evaluated in a single center from January 2012 to May 2018. Two groups were identified: the first consisted of pregnancies that underwent in-utero repair (IUR) and the second those that had postnatal repair (PNR). Penalized B splines were used to determine the trend in VS, across 2-week gestational-age (GA) epochs, between 24 and 36 weeks of gestation. VS at each GA epoch and the change in VS between each GA epoch were compared between the IUR and PNR groups. To determine whether VS at any GA was predictive of VPS, receiver-operating-characteristics (ROC) curves were used and the optimal cut-off at each GA epoch was identified. Univariate analysis and multiple logistic regression were used for further analysis.

RESULTS

ONTD was diagnosed in 110 fetuses, of whom 69 underwent IUR and 41 had PNR. Fetuses in the IUR group were more likely to have Chiari II malformation (100.0% vs 82.9%; P < 0.01), lower GA at delivery (34.9 ± 3.2 vs 37.1 ± 2.1 weeks; P < 0.01) and lower rates of VPS within the first year postpartum (36.2% vs 61.0%; P = 0.02) compared with the PNR group. In both groups, VS increased steadily with GA from the initial evaluation to delivery. In the IUR group, there was a significant change in VS between the 24 + 0 to 25 + 6-week and the 26 + 0 to 27 + 6-week epochs (2.3 (95% CI, 0.4-4.1) mm; P = 0.02). There was a positive trend in the change in VS at later GAs, but this was not significant. Although there was no significant change in VS in the PNR group before 30 weeks, there was a positive trend after that time. On multivariate analysis, each week of advancing GA was associated with a mean increase of 0.74 mm in VS (P < 0.0001) in both groups. VS was not associated with the level or type of lesion, but presence of Chiari II malformation was associated with a mean increase of 5.88 mm (P < 0.0001) in VS in both the IUR and PNR groups. VS was modestly predictive of need for VPS in both groups, with area under ROC curves between 0.68 and 0.76 at the different GA epochs. Change in VS between the first and last measurements was also modestly predictive of the need for VPS, with better performance in the PNR group.

CONCLUSIONS

VS increased with advancing GA in all fetuses with ONTD, although in the IUR group this increase occurred immediately after fetal surgery and in the PNR group it occurred after 30 weeks of gestation. In-utero surgery was associated with a decreased rate of VPS and was more predictive of need for VPS than was VS. Postnatal factors resulting in increased need for VPS in the PNR group need to be assessed further. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Deficiency of the oxidative stress-responsive kinase p70S6K1 restores autophagy and ameliorates neural tube defects in diabetic embryopathy

BACKGROUND

Autophagy is highly active in neuroepithelial cells of the developing neuroepithelium, and impairment of autophagy leads to neural tube defects. In this study, we have found that maternal diabetes suppresses autophagy that leads to neural tube defects and consequent cellular imbalance in the endoplasmic reticulum where critical events occur, leading to the induction of diabetic embryopathy. Because the mammalian target of rapamycin pathway suppresses autophagy, we hypothesized that 70 kDa ribosomal protein S6 kinase 1 (p70S6K1), a major downstream effector of mammalian target of rapamycin, mediates the inhibitory effect of maternal diabetes on autophagy in the developing neuroepithelium.

OBJECTIVE

We investigated whether p70S6K1 mediates the inhibitory effect of maternal diabetes on autophagy during neurulation. We also examined whether p70S6K1 deficiency restores autophagy and therefore relieves endoplasmic reticulum stress and inhibits maternal diabetes-induced apoptosis, which leads to reduction in neural tube defect incidence in diabetic embryopathy.

STUDY DESIGN

Female p70S6K1 heterogeneous knockout (p70S6K1+/-) mice were bred with male p70S6K1 heterogeneous knockout (p70S6K1+/-) mice to generate wild-type (WT), p70S6K1+/- and p70S6K1 knockout (p70S6K1-/-) embryos. Embryos at embryonic day 8.5 were harvested for the assessment of indices of autophagy, endoplasmic reticulum stress, and apoptosis. Neural tube defect incidence in embryos was determined at embryonic day 10.5. For in vitro studies, small interfering RNA knockdown of p70S6K1 in C17.2 mouse neural stem cells was used to determine the effect of p70S6K1 deficiency on autophagy impairment and endoplasmic reticulum stress under high glucose conditions.

RESULTS

Knockout of the Rps6kb1 gene, which encodes for p70S6K1, ameliorated maternal diabetes-induced NTDs and restored autophagosome formation in neuroepithelial cells suppressed by maternal diabetes. Maternal diabetes-suppressed conversion of LC3-I (microtubule-associated protein 1A/1B-light chain 3) to LC3-II, an index of autophagic activity, in neurulation stage embryos was abrogated in the absence of p70S6K1. p70S6K1 knockdown in neural stem cells also restored autophagosome formation and the conversion of LC3-I to LC3-II. The activation of the major unfolded protein response, indicated by phosphorylation of inositol-requiring enzyme 1 alpha, and protein kinase R-like endoplasmic reticulum kinase, and eukaryotic translation initiation factor 2α, and the increase of the endoplasmic reticulum stress marker, C/EBP homologous protein, were induced by maternal diabetes in vivo and high glucose in vitro. Unfolded protein response and endoplasmic reticulum stress induced by maternal diabetes or high glucose were reduced by Rps6kb1 deletion or p70S6K1 knockdown, respectively. Rps6kb1 knockout blocked maternal diabetes-induced caspase cleavage and neuroepithelial cell apoptosis. The superoxide dismutase mimetic Tempol abolished high glucose-induced p70S6K1 activation.

CONCLUSION

The study revealed the critical involvement of p70S6K1 in the pathogenesis of diabetic embryopathy.

Comparison of two fetoscopic open neural tube defect repair techniques: single- vs three-layer closure

OBJECTIVES

We reported previously on an exteriorized-uterus fetoscopic repair for open neural tube defect (ONTD) using a single-layer closure (SLC) technique. However, because SLC was associated with a high rate of cerebrospinal fluid (CSF) leakage at birth, we developed a three-layer closure (3LC) technique comprising a bovine collagen patch, a myofascial layer and a skin layer. The aims of this study were to compare SLC and 3LC in terms of intraoperative, postoperative and obstetric outcomes, as well as short-term neonatal neurologic and non-neurologic outcomes.

METHODS

This was a retrospective analysis of prospectively collected data, from 32 consecutive SLC controls and 18 consecutive 3LC cases, that underwent exteriorized-uterus two-port fetoscopic repair of ONTD at our center, between April 2014 and December 2018. All patients satisfied the Management of Myelomeningocele Study (MOMS) criteria. Obstetric, maternal, fetal and early neonatal outcomes were compared between the SLC and 3LC groups.

RESULTS

Maternal demographics and mean gestational age (GA) at fetal surgery (25.0 ± 0.7 vs 25.0 ± 0.5 weeks' gestation; P = 0.96), and at delivery (36.5 ± 3.5 vs 37.6 ± 3.0 weeks; P = 0.14), were similar between the SLC and 3LC groups, respectively. The rate of preterm prelabor rupture of membranes (PPROM) < 37 weeks (28% vs 29%; P = 0.9), mean GA at PPROM (32.3 ± 3.4 vs 32.7 ± 1.9 weeks; P = 0.83) and rate of vaginal delivery (50% vs 47%; P = 0.84) were similar for the SLC vs 3LC groups, respectively. In pregnancies that had SLC compared with those that had 3LC, there was a significantly higher incidence of CSF leakage at birth (8/32 (25%) vs 0/17 (0%); P = 0.02) and a significantly lower rate of reversal of hindbrain herniation at 6 weeks postoperatively (18/30 (60%) vs 14/15 (93%); P = 0.02). The rate of infants that met the MOMS criteria for shunt placement or died before 12 months of age (23/31 (74%) vs 7/12 (58%); P = 0.31) and those that required treatment for hydrocephalus by 12 months (15/32 (47%) vs 4/12 (33%); P = 0.42) were similar between the SLC and 3LC groups, respectively.

CONCLUSIONS

Compared to SLC, 3LC preserves the fetal and obstetric benefits of fetoscopic repair and shows improved rates of CSF leakage and reversal of hindbrain herniation at 6 weeks postoperatively. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

F-box protein FBXO30 mediates retinoic acid receptor γ ubiquitination and regulates BMP signaling in neural tube defects

Retinoic acid (RA), an active derivative of vitamin A, is critical for the neural system development. During the neural development, the RA/RA receptor (RAR) pathway suppresses BMP signaling-mediated proliferation and differentiation of neural progenitor cells. However, how the stability of RAR is regulated during neural system development and how BMP pathway genes expression in neural tissue from human fetuses affected with neural tube defects (NTDs) remain elusive. Here, we report that FBXO30 acts as an E3 ubiquitin ligase and targets RARγ for ubiquitination and proteasomal degradation. In this way, FBXO30 positively regulates BMP signaling in mammalian cells. Moreover, RA treatment leads to suppression of BMP signaling by reducing the level of FBXO30 in mammalian cells and in mouse embryos with NTDs. In samples from human NTDs with high levels of retinol, downregulation of BMP target genes was observed, along with aberrant FBXO30 levels. Collectively, our results demonstrate that RARγ levels are controlled by FBXO30-mediated ubiquitination and that FBXO30 is a key regulator of BMP signaling. Furthermore, we suggest a novel mechanism by which high-retinol levels affect the level of FBXO30, which antagonizes BMP signaling during early stage development.

Posterior axis formation requires Dlx5/Dlx6 expression at the neural plate border

Neural tube defects (NTDs), one of the most common birth defects in human, present a multifactorial etiology with a poorly defined genetic component. The Dlx5 and Dlx6 bigenic cluster encodes two evolutionary conserved homeodomain transcription factors, which are necessary for proper vertebrate development. It has been shown that Dlx5/6 genes are essential for anterior neural tube closure, however their role in the formation of the posterior structures has never been described. Here, we show that Dlx5/6 expression is required during vertebrate posterior axis formation. Dlx5 presents a similar expression pattern in neural plate border cells during posterior neurulation of zebrafish and mouse. Dlx5/6-inactivation in the mouse results in a phenotype reminiscent of NTDs characterized by open thoracic and lumbar vertebral arches and failure of epaxial muscle formation at the dorsal midline. The dlx5a/6a zebrafish morphants present posterior NTDs associated with abnormal delamination of neural crest cells showing altered expression of cell adhesion molecules and defects of motoneuronal development. Our findings provide new molecular leads to decipher the mechanisms of vertebrate posterior neurulation and might help to gather a better understanding of human congenital NTDs etiology.

Neural Tube Defects in Embryonic Life: Lessons Learned From 340 Early Pregnancy Failures

OBJECTIVES

The aim of this study was to evaluate the feasibility of sonographic assessment of the embryonic/fetal neural tube in nonviable pregnancies and to determine the defect incidence.

METHODS

Prospective analysis of transvaginally acquired 3-dimensional (3D) multiplanar and 3D surface-rendered volume sets of 340 cases of missed abortion between March 2010 and September 2015 was performed. Data regarding karyotype and postmortem examination as well as demographic features and the outcomes of subsequent pregnancies were evaluated.

RESULTS

In 223 cases, an embryo/fetus was detected and considered suitable for further evaluation: in 37 of 223 (16.6%) embryos/fetuses, a neural tube defect was present: 27 of 37 cephaloceles, 5 of 37 anencephalies/exencepahlies, 3 of 37 spina bifidas, 1 of 37 caudal regression syndrome, and 1 of 37 iniencephaly. Additional alterations were not observed. In 7 of 37 cases karyotyping was carried out and showed no aneuploidy. Eight subsequent pregnancies had a favorable outcome, with 1 ending in an intrauterine fetal death during the 22nd week of gestation. Maternal folic acid supplementation was provided for all subsequent pregnancies. No neural tube defects occurred.

CONCLUSIONS

Sonographic 3D evaluation of complete neural tube closure in embryonic/fetal demise is technically feasible and can be achieved in embryos with a crown-rump length greater than 8 mm. In 26 of 37 cases a defective closure site could be allocated to high-risk areas known for early embryonic demise. Regardless of the etiology of different neural tube defects, high-dose folic acid prophylaxis must be recommended in all cases. Sonographic evaluation of the neural tube, including 3D surface-rendered images, should be offered to every woman with a missed abortion because of the impact on subsequent pregnancies.

Molecular cytogenetic characterization of a duplication of 15q24.2-q26.2 associated with anencephaly and neural tube defect

OBJECTIVE

We present molecular cytogenetic characterization of a duplication of 15q24.2-q26.2 associated with anencephaly and neural tube defect (NTD).

CASE REPORT

A 35-year-old pregnant woman was found to have a fetus with anencephaly by prenatal ultrasound at 12 weeks of gestation. The pregnancy was subsequently terminated, and a malformed fetus was delivered with anencephaly. Cytogenetic analysis of the cultured placental tissues revealed a karyotype of 46,XX,dup(15) (q24.2q26.2). Parental karyotypes were normal. Array comparative genomic hybridization analysis of the placental tissues revealed a 20.36-Mb duplication of 15q24.2-q26.2 encompassing 100 Online Mendelian Inheritance of in Man (OMIM) genes including LINGO1, MTHFS, KIF7 and CHD2. Metaphase fluorescence in situ hybridization analysis using 15q25.1-specidic probe confirmed a duplication of 15q25.1. Polymorphic DNA marker analysis showed a maternal origin of the duplication.

CONCLUSION

A duplication of chromosome 15q24.2-q26.2 can be associated with NTD.

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.

Embryology of the craniocervical junction and posterior cranial fossa, part II: Embryogenesis of the hindbrain

Although pathology of the hindbrain and its derivatives can have life altering effects on a patient, a comprehensive review on its embryology is difficult to find in the peer-reviewed medical literature. Therefore, this review article, using standard search engines, seemed timely. The embryology of the hindbrain is complex and relies on a unique timing of various neurovascular and bony elements. Derailment of these developmental processes can lead to a wide range of malformations such as the Chiari malformations. Therefore, a good working knowledge of this embryology as outlined in this review of the hindbrain is important for those treating patients with involvement of this region of the central nervous system. Clin. Anat. 31:488-500, 2018. © 2018 Wiley Periodicals, Inc.

[Localization of gestational age reference table and its application in prenatal screening]

Objective: To establish a fetal biparietal diameter (BPD)-gestational age formula based on the data of pregnant women from Xiaoshan District of Hangzhou, and to evaluate its application in prenatal screening. Methods: Data of 3500 pregnant women with gestational age between 15 weeks and 19 weeks+6 receiving prenatal screening in Xiaoshan Hospital during May 2014 and May 2015 were collected. BPDs were used to establish a localized BPD-gestational age formula. The localized formula was used to evaluate the prenatal screening risks in 1759 pregnant women with irregular menstrual cycles or uncertain last menstrual period (LMP) in Xiaoshan District, and the results were compared with those calculated using formula in LifeCycle 4.0. Results: With localized formula, the total positive rate of Down syndrome, trisomy 18 syndrome and deformity of neural tube was decreased from 6.96% to 5.85% ( P<0.05), in which the positive rate of Down syndrome decreased ( P<0.05), that of deformity of neural tube increased ( P<0.05), and that of trisomy 18 syndrome remained the same ( P>0.05). The median MoMs of free-hCG β and α-fetoprotein calculated using localized formula were significantly different from those calculated using the formula in LifeCycle 4.0 (all P<0.05), and the former ones were more closer to 1. For women of fetus diagnosed with the above diseases, the positive rate calculated using localized formula was almost the same as that calculated using the formula in LifeCycle 4.0. Conclusion: BPD-gestational age formula should be localized based on the statistical analysis of the local population, which will help to reduce the false positive rate, and make the results more accurate and reliable in prenatal screening.

Fetuses with Neural Tube Defects: ethical approaches and the role of health care professionals in Turkish health care institutions

Neural tube defects (NTDs) are very serious malformations for the fetus, causing either low life expectancy or a chance of survival only with costly and difficult surgical interventions. In western countries the average prevalence is 1/1000-2000 and in Turkey it is 4/1000. The aim of the study was to characterize ethical approaches at institutional level to the fetus with an NTD and the mother, and the role of health care professionals in four major centers in Turkey. The authors chose perinatology units of four university hospitals and prepared questionnaires for the responsible professionals concerning their own and their institution’s ethical approaches to the fetus with an NTD and the mother. The investigation revealed that there were no institutional ethical frameworks or ethics committees available to professional teams in the units. The roles of the health care professionals and their individual decisions and approaches based on ethical principles are described. The ethical decision-making process concerning fetuses with NTDs, examples of institutional approaches to the topic and institutional frameworks, and the role of nurses and other health care professionals are all discussed, based on a literature review. The authors suggest that institutional ethical frameworks, ethics committees, professionals’ ethics education and multidisciplinary teamwork should be established for critical situations such as fetuses with an NTD.

High Glucose-Repressed CITED2 Expression Through miR-200b Triggers the Unfolded Protein Response and Endoplasmic Reticulum Stress

High glucose in vivo and in vitro induces neural tube defects (NTDs). CITED2 (CBP/p300-interacting transactivator with ED-rich tail 2) is essential for neural tube closure. We explored the regulatory mechanism underlying CITED2 expression and its relationship with miRNA and endoplasmic reticulum (ER) stress. miR-200b levels were increased by maternal diabetes or high glucose in vitro, and this increase was abrogated by transgenic overexpression of superoxide dismutase 1 (SOD1) or an SOD1 mimetic. CITED2 was the target of miR-200b and was downregulated by high glucose. Two miR-200b binding sites in the 3'-untranslated region of the CITED2 mRNA were required for inhibiting CITED2 expression. The miR-200b mimic and a CITED2 knockdown mimicked the stimulative effect of high glucose on unfolded protein response (UPR) and ER stress, whereas the miR-200b inhibitor and CITED2 overexpression abolished high glucose-induced UPR signaling, ER stress, and apoptosis. The ER stress inhibitor, 4-phenylbutyrate, blocked CITED2 knockdown-induced apoptosis. Furthermore, the miR-200b inhibitor reversed high glucose-induced CITED2 downregulation, ER stress, and NTDs in cultured embryos. Thus, we showed a novel function of miR-200b and CITED2 in high glucose-induced UPR and ER stress, suggesting that miR-200b and CITED2 are critical for ER homeostasis and NTD formation in the developing embryo.

Dominant negative FADD dissipates the proapoptotic signalosome of the unfolded protein response in diabetic embryopathy

Endoplasmic reticulum (ER) stress and caspase 8-dependent apoptosis are two interlinked causal events in maternal diabetes-induced neural tube defects (NTDs). The inositol-requiring enzyme 1α (IRE1α) signalosome mediates the proapoptotic effect of ER stress. Diabetes increases tumor necrosis factor receptor type 1R-associated death domain (TRADD) expression. Here, we revealed two new unfolded protein response (UPR) regulators, TRADD and Fas-associated protein with death domain (FADD). TRADD interacted with both the IRE1α-TRAF2-ASK1 complex and FADD. In vivo overexpression of a FADD dominant negative (FADD-DN) mutant lacking the death effector domain disrupted diabetes-induced IRE1α signalosome and suppressed ER stress and caspase 8-dependent apoptosis, leading to NTD prevention. FADD-DN abrogated ER stress markers and blocked the JNK1/2-ASK1 pathway. Diabetes-induced mitochondrial translocation of proapoptotic Bcl-2 members mitochondrial dysfunction and caspase cleavage were also alleviated by FADD-DN. In vitro TRADD overexpression triggered UPR and ER stress before manifestation of caspase 3 and caspase 8 cleavage and apoptosis. FADD-DN overexpression repressed high glucose- or TRADD overexpression-induced IRE1α phosphorylation, its downstream proapoptotic kinase activation and endonuclease activities, and apoptosis. FADD-DN also attenuated tunicamycin-induced UPR and ER stress. These findings suggest that TRADD participates in the IRE1α signalosome and induces UPR and ER stress and that the association between TRADD and FADD is essential for diabetes- or high glucose-induced UPR and ER stress.

Decoding the oxidative stress hypothesis in diabetic embryopathy through proapoptotic kinase signaling

Maternal diabetes-induced birth defects occur in 6-10% of babies born to mothers with pregestational diabetes, representing a significant maternal-fetal health problem. Currently, these congenital malformations represent a significant maternal-fetal medicine issue, but are likely to create an even greater public health threat as 3 million women of reproductive age (19-44 years) have diabetes in the United States alone, and this number is expected to double by 2030. Neural tube defects (NTDs) and congenital heart defects are the most common types of birth defects associated with maternal diabetes. Animal studies have revealed that embryos under hyperglycemic conditions exhibit high levels of oxidative stress resulting from enhanced production of reactive oxygen species and impaired antioxidant capability. Oxidative stress activates a set of proapoptotic kinase signaling intermediates leading to abnormal cell death in the embryonic neural tube, which causes NTD formation. Work in animal models also has revealed that maternal diabetes triggers a series of signaling intermediates: protein kinase C (PKC) isoforms, PKCα, βII and δ; apoptosis signal-regulating kinase 1; c-Jun-N-terminal kinase (JNK)1/2; caspase; and apoptosis. Specifically, maternal diabetes in rodent models activates the proapoptotic unfolded protein response and endoplasmic reticulum (ER) stress. A reciprocal causation between JNK1/2 activation and ER stress exists in diabetic embryopathy. Molecular studies further demonstrate that deletion of the genes for Prkc, Ask1, Jnk1, or Jnk2 abolishes maternal diabetes-induced neural progenitor apoptosis and ameliorates NTD formation. Similar preventive effects are also observed when apoptosis signal-regulating kinase 1, JNK1/2, or ER stress is inhibited. Cell membrane stabilizers and antioxidant supplements are also effective in prevention of diabetes-induced birth defects. Mechanistic studies have revealed important insights into our understanding the cause of diabetic embryopathy and have provided a basis for future interventions against birth defects or other pregnancy complications associated with maternal diabetes. The knowledge of a molecular pathway map identified in animal studies has created unique opportunities to identify molecular targets for therapeutic intervention.

Orally administered melatonin prevents lipopolysaccharide-induced neural tube defects in mice

Lipopolysaccharide (LPS) has been associated with adverse pregnant outcomes, including fetal demise, intra-uterine growth restriction (IUGR), neural tube defects (NTDs) and preterm delivery in rodent animals. Previous studies demonstrated that melatonin protected against LPS-induced fetal demise, IUGR and preterm delivery. The aim of the present study was to investigate the effects of melatonin on LPS-induced NTDs. All pregnant mice except controls were intraperitoneally injected with LPS (25 µg/kg) daily from gestational day (GD)8 to GD12. Some pregnant mice were orally administered with melatonin (MT, 50 mg/kg) before each LPS injection. A five-day LPS injection resulted in 27.5% of fetuses with anencephaly, exencephaly or encephalomeningocele. Additional experiment showed that maternal LPS exposure significantly down-regulated placental proton-coupled folate transporter (pcft) and disturbed folate transport from maternal circulation through the placentas into the fetus. Interestingly, melatonin significantly attenuated LPS-induced down-regulation of placental pcft. Moreover, melatonin markedly improved the transport of folate from maternal circulation through the placentas into the fetus. Correspondingly, orally administered melatonin reduced the incidence of LPS-induced anencephaly, exencephaly or encephalomeningocele. Taken together, these results suggest that orally administered melatonin prevents LPS-induced NTDs through alleviating LPS-induced disturbance of folate transport from maternal circulation through the placenta into the fetus.

Folic acid supplementation in pregnancy and implications in health and disease

Maternal exposure to dietary factors during pregnancy can influence embryonic development and may modulate the phenotype of offspring through epigenetic programming. Folate is critical for nucleotide synthesis, and preconceptional intake of dietary folic acid (FA) is credited with reduced incidences of neural tube defects in infants. While fortification of grains with FA resulted in a positive public-health outcome, concern has been raised for the need for further investigation of unintended consequences and potential health hazards arising from excessive FA intakes, especially following reports that FA may exert epigenetic effects. The objective of this article is to discuss the role of FA in human health and to review the benefits, concerns and epigenetic effects of maternal FA on the basis of recent findings that are important to design future studies.

Valproic acid substantially downregulated genes folr1, IGF2R, RGS2, COL6A3, EDNRB, KLF6, and pax-3, N-acetylcysteine alleviated most of the induced gene alterations in chicken embryo model

Valproic acid induced teratogenicity at genetic and somatic levels, the action mechanism is still unclear. We hypothesized that folate receptor gene (folr1) and others may be interacting to elicit neural tube defect (NTD), while N-acetylcysteine (NAC) may be beneficial for protection. In chicken embryo model, the experiment was conducted in two parts. The first part was carried out to test the optimum dose of VPA. The second part was conducted to test the protective effect of NAC at doses 10 and 20 mM. VPA induced dysvascularization, incomplete somite enclosure, histone deacetylase (HDAC) inhibition, folate deficiency, homocysteine accumulation, SOD inhibition, glutathione depletion, elevated MDA and hydrogen peroxide. NAC alleviated most of these adverse effects. The microarray analysis revealed 17 genes downregulated and four upregulated. The relevancy covered translation (23%), signal transduction (23%), transcription (16%), cell adhesion (16%), neural cell migration (8%), transport (7%), and organismal development (7%). The genes insulin-like growth factor 2 receptor gene (IGF2R), regulator of G-protein signaling 4 gene (RGS4), alpha 3 (VI) collagen gene (COL6A3), endothelin receptor type b gene (EDNRB), and Krüppel-like factor 6 gene (KLF6) substantially downregulated in reality were directly intermodulating and associated with NTD. VPA downregulated folr1 gene in a dose responsive manner without affecting pax-3 gene, which was ascribed to the metahypoxic state. Conclusively, VPA affects 21 genes: 17 downregulated and four upregulated. VPA dose responsively downregulates gene folr1 without affecting pax-3 gene. These adverse effects can be partially alleviated by N-acetylcysteine.

Cdon mutation and fetal ethanol exposure synergize to produce midline signaling defects and holoprosencephaly spectrum disorders in mice

Holoprosencephaly (HPE) is a remarkably common congenital anomaly characterized by failure to define the midline of the forebrain and midface. HPE is associated with heterozygous mutations in Sonic hedgehog (SHH) pathway components, but clinical presentation is extremely variable and many mutation carriers are unaffected. It has been proposed that these observations are best explained by a multiple-hit model, in which the penetrance and expressivity of an HPE mutation is enhanced by a second mutation or the presence of cooperating, but otherwise silent, modifier genes. Non-genetic risk factors are also implicated in HPE, and gene-environment interactions may provide an alternative multiple-hit model to purely genetic multiple-hit models; however, there is little evidence for this contention. We report here a mouse model in which there is dramatic synergy between mutation of a bona fide HPE gene (Cdon, which encodes a SHH co-receptor) and a suspected HPE teratogen, ethanol. Loss of Cdon and in utero ethanol exposure in 129S6 mice give little or no phenotype individually, but together produce defects in early midline patterning, inhibition of SHH signaling in the developing forebrain, and a broad spectrum of HPE phenotypes. Our findings argue that ethanol is indeed a risk factor for HPE, but genetically predisposed individuals, such as those with SHH pathway mutations, may be particularly susceptible. Furthermore, gene-environment interactions are likely to be important in the multifactorial etiology of HPE.

[Intracerebral neurenteric cysts in newborn infants]

INTRODUCTION

Intracranial neurenteric cysts are very infrequent congenital lesions. Within the nervous system, they are most commonly located in the rachis. Another frequent site is the craniocervical junction. Few cases of supratentorial location have been reported. A differential diagnosis is required to distinguish them from other cysts. They are not often diagnosed in the paediatric age. The clinical features they give rise to are due to the mass effect or episodes of chemical meningitis. Magnetic resonance imaging is the best diagnostic method although on many occasions they cannot be distinguished from arachnoid cysts. Treatment consists in surgery with complete resection of the membranes in order to prevent recurrences.

CASE REPORTS

We report two cases of infants who, in the last weeks of gestation, presented supratentorial intracerebral cystic lesions that resembled arachnoid cysts. A neonatal magnetic resonance scan confirmed the existence of such supratentorial cysts with septae inside them. After presenting an increase in the cranial perimeter, surgical treatment was undertaken with a neuronavigation-guided craniotomy and debridement of the cysts. The cysts contain mucus and have thick membranes. Pathological study results are consistent with a neurenteric cyst. One of the patients presented complete resolution after the intervention with good cerebral expansion. In the second case, there was persistence of an adjoining arachnoid cyst, in which placement of a cyst-peritoneal shunt was necessary with full resolution.

CONCLUSIONS

Most intracranial cysts are arachnoid cysts, but there are other cystic lesions that must be treated by surgical means so that they can be completely excised and sent for pathological analyses.

Murine dishevelled 3 functions in redundant pathways with dishevelled 1 and 2 in normal cardiac outflow tract, cochlea, and neural tube development

Dishevelled (Dvl) proteins are important signaling components of both the canonical β-catenin/Wnt pathway, which controls cell proliferation and patterning, and the planar cell polarity (PCP) pathway, which coordinates cell polarity within a sheet of cells and also directs convergent extension cell (CE) movements that produce narrowing and elongation of the tissue. Three mammalian Dvl genes have been identified and the developmental roles of Dvl1 and Dvl2 were previously determined. Here, we identify the functions of Dvl3 in development and provide evidence of functional redundancy among the three murine Dvls. Dvl3^−/− mice died perinatally with cardiac outflow tract abnormalities, including double outlet right ventricle and persistent truncus arteriosis. These mutants also displayed a misorientated stereocilia in the organ of Corti, a phenotype that was enhanced with the additional loss of a single allele of the PCP component Vangl2/Ltap (LtapLp/+). Although neurulation appeared normal in both Dvl3^−/− and LtapLp/+ mutants, Dvl3^+/−;LtapLp/+ combined mutants displayed incomplete neural tube closure. Importantly, we show that many of the roles of Dvl3 are also shared by Dvl1 and Dvl2. More severe phenotypes were observed in Dvl3 mutants with the deficiency of another Dvl, and increasing Dvl dosage genetically with Dvl transgenes demonstrated the ability of Dvls to compensate for each other to enable normal development. Interestingly, global canonical Wnt signaling appeared largely unaffected in the double Dvl mutants, suggesting that low Dvl levels are sufficient for functional canonical Wnt signals. In summary, we demonstrate that Dvl3 is required for cardiac outflow tract development and describe its importance in the PCP pathway during neurulation and cochlea development. Finally, we establish several developmental processes in which the three Dvls are functionally redundant.

Multi-gene families, comprising a set of very similar genes with shared nucleotide sequences, are common in mammals. Individual family members may be expressed in different places and perform separate functions. Alternatively, the genes may have redundant functions, but distinct dosage requirements. Mammals share three Dishevelled (Dvl) family members and while the roles of Dvl1 and Dvl2 have been described previously, the functions of Dvl3 have remained elusive. Here, we show that the lack of Dvl3 in mice affects the formation of the heart, neural tube, and inner ear. We further show that the defects in these tissues are much more severe when the mice are deficient in more than one Dvl family member, indicating redundant functions for these genes. Congenital heart disease affects approximately 75 in every 1,000 live human births, and approximately 30% of these diseases are due to disruptions in the outflow tract, the region affected in mice lacking Dvl genes. Neural tube defects, similar to those observed in the Dvl mutants, are also common in humans. The animal models described here provide useful tools to elucidate the genetic mechanisms that underlie these abnormalities and may provide novel ways of treating these disorders in the future.

Targeted disruption of Mib2 causes exencephaly with a variable penetrance

Mib1 and Mib2 ubiquitin ligases are very similar in their domain construction. They partake in the Notch signaling pathway by ubiquitinating the Notch receptors Delta and Jagged prior to endocytosis. We have created a targeted mutation of Mib2 and show that its phenotype is a variable penetrance, failure to close the cranial neural tube. The penetrance depends on the genetic background but it appears that Mib2 is not completely essential in mouse development.

Embryology of neural tube defects: information provided by associated malformations

OBJECTIVES

To get information about embryologic mechanisms of neural tube defects (NTD), by studying the associated malformations.

METHODS

Eighty three cases of NTD, seen at the prenatal diagnosis unit of Rennes University Hospital (France) between May 1999 and December 2002, were retrospectively studied. Cases with chromosomal anomalies (5/83), cases without available karyotype or pathologic examination were excluded. 24 spina bifida, and 27 cephalic forms (anencephalies, exencephalies, and encephaloceles) were thus analyzed.

RESULTS

Only 22/51 cases (43%) were strictly isolated NTD. Anomalies of tissues arising from neural crests were noted in 8/51 fetuses (16%), midline or lateralization anomalies in 12/51 (24%), and anomalies of mesoblastic tissues in 17/51 (33%). An already known syndrome was found in 4/51 cases (8%).

CONCLUSION

NDT are more extensive congenital damages that would suggest the restrictive terminology. That prompts to assess cautiously prenatal diagnosis of NTD, and to get detailed pathological examination after termination of pregnancy.

Intramedullary dermoid in a low lying conus tethered by a fatty filum - embryological implications

Intramedullary dermoids arising within the conus medullaris are rare. We report a rare association of an intramedullary dermoid cyst located in a low lying conus tethered by a thickened, fatty filum terminale and discuss the embryological implications of this association.

Modifier locus for exencephaly inCecr2mutant mice is syntenic to the 10q25.3 region associated with neural tube defects in humans

Neural tube defects (NTDs), the second most common birth defect in humans, are multifactorial with complex genetic and environmental causes, although the genetic factors are almost completely unknown. In mice, >100 single gene mutations cause NTDs; however, the penetrance in many of these single gene mutant lines is highly dependent on the genetic background. We previously reported that a homozygous Cecr2 mutation on a BALB/c background causes exencephaly at a frequency of 74% compared with 0% on an FVB/N background. We now report that a major genetic modifier on chromosome 19, mapped using whole genome linkage analysis, increases the relative risk of exencephaly by 3.74 times in homozygous BALB embryos vs. BALB/FVB heterozygotes. Scanning electron microscopy revealed that the modifier does not affect the location of neural tube closure site 2, a known murine susceptibility factor for exencephaly. Crossing the Sp ( Splotch) mutation in the Pax3 gene onto the FVB/N background for two generations indicated that this resistant strain also decreases the penetrance of spina bifida. The chromosome 19 modifier region corresponds to a linkage region on human chromosome 10q25.3 mapped in a whole genome scan of human NTD families. Since the FVB/N genetic background affects susceptibility to both exencephaly and spina bifida, the human homolog of the chromosome 19 modifier locus may be a better candidate for human NTD susceptibility factors than genes that when mutated actually cause NTDs in mice.

Genetic models of mammalian neural tube defects

Several mouse mutations disturb the embryonic process of neurulation, yielding neural tube defects. Analysis of the mutations offers the most feasible approach to understanding the aetiology and pathogenesis of human neural tube defects. Interactions between the non-allelic mutant genes and between several of the mutant genes and modifying genes in the genetic background modulate the frequency and severity of the defects that develop. Environmental factors interact with the genetic predisposition either to increase or to decrease the incidence of defects. The gene loci corresponding to two of the mutations, splotch (Sp) and extra toes (Xt), have been identified as those encoding the transcription factors Pax-3 and Gli3, respectively; their human homologues are associated with Waardenburg type I syndrome and Greig's cephalopolysyndactyly. Embryological analysis reveals that several of the mutations disturb the process of neural tube closure at the posterior neuropore (in the lumbosacral region), yielding spina bifida and/or tail defects. The different mutations appear to achieve this developmental end-point by different underlying mechanisms. In curly tail (ct), non-neural tissues proliferate abnormally slowly causing ventral curvature of the neuropore region and inhibiting neural tube closure. Neural tube defects can be prevented in cultured ct/ct embryos by experimentally correcting either the proliferative imbalance or the ventral curvature. In Sp the primary defect appears to reside in the neuroepithelium. A combination of genetic analysis, gene cloning and experimental embryology is revealing that neural tube defects in mice and, by implication, in humans are a developmentally heterogeneous group of malformations.

Loss of the Atp2c1 secretory pathway Ca(2+)-ATPase (SPCA1) in mice causes Golgi stress, apoptosis, and midgestational death in homozygous embryos and squamous cell tumors in adult heterozygotes

Loss of one copy of the human ATP2C1 gene, encoding SPCA1 (secretory pathway Ca(2+)-ATPase isoform 1), causes Hailey-Hailey disease, a skin disorder. We performed targeted mutagenesis of the Atp2c1 gene in mice to analyze the functions of this Golgi membrane Ca(2+) pump. Breeding of heterozygous mutants yielded a normal Mendelian ratio among embryos on gestation day 9.5; however, null mutant (Spca1(-/-)) embryos exhibited growth retardation and did not survive beyond gestation day 10.5. Spca1(-/-) embryos had an open rostral neural tube, but hematopoiesis and cardiovascular development were ostensibly normal. Golgi membranes of Spca1(-/-) embryos were dilated, had fewer stacked leaflets, and were expanded in amount, consistent with increased Golgi biogenesis. The number of Golgi-associated vesicles was also increased, and rough endoplasmic reticulum had fewer ribosomes. Coated pits, junctional complexes, desmosomes, and basement membranes appeared normal in mutant embryos, indicating that processing and trafficking of proteins in the secretory pathway was not massively impaired. However, apoptosis was increased, possibly the result of secretory pathway stress, and a large increase in cytoplasmic lipid was observed in mutant embryos, consistent with impaired handling of lipid by the Golgi. Adult heterozygous mice appeared normal and exhibited no evidence of Hailey-Hailey disease; however, aged heterozygotes had an increased incidence of squamous cell tumors of keratinized epithelial cells of the skin and esophagus. These data show that loss of the Golgi Ca(2+) pump causes Golgi stress, expansion of the Golgi, increased apoptosis, and embryonic lethality and demonstrates that SPCA1 haploinsufficiency causes a genetic predisposition to cancer.

Ambra1 regulates autophagy and development of the nervous system

Autophagy is a self-degradative process involved both in basal turnover of cellular components and in response to nutrient starvation or organelle damage in a wide range of eukaryotes. During autophagy, portions of the cytoplasm are sequestered by double-membraned vesicles called autophagosomes, and are degraded after fusion with lysosomes for subsequent recycling. In vertebrates, this process acts as a pro-survival or pro-death mechanism in different physiological and pathological conditions, such as neurodegeneration and cancer; however, the roles of autophagy during embryonic development are still largely uncharacterized. Beclin1 (Becn1; coiled-coil, myosin-like BCL2-interacting protein) is a principal regulator in autophagosome formation, and its deficiency results in early embryonic lethality. Here we show that Ambra1 (activating molecule in Beclin1-regulated autophagy), a large, previously unknown protein bearing a WD40 domain at its amino terminus, regulates autophagy and has a crucial role in embryogenesis. We found that Ambra1 is a positive regulator of the Becn1-dependent programme of autophagy, as revealed by its overexpression and by RNA interference experiments in vitro. Notably, Ambra1 functional deficiency in mouse embryos leads to severe neural tube defects associated with autophagy impairment, accumulation of ubiquitinated proteins, unbalanced cell proliferation and excessive apoptotic cell death. In addition to identifying a new and essential element regulating the autophagy programme, our results provide in vivo evidence supporting the existence of a complex interplay between autophagy, cell growth and cell death required for neural development in mammals.

Toward understanding the genetic basis of neural tube defects

Neural tube defects (NTDs) represent a common group of severe congenital malformations that result from failure of neural tube closure during early development. Their etiology is quite complex involving environmental and genetic factors and their underlying molecular and cellular pathogenic mechanisms remain poorly understood. Animal studies have recently demonstrated an essential role for the planar cell polarity pathway (PCP) in mediating a morphogenetic process called convergent extension during neural tube formation. Alterations in members of this pathway lead to NTDs in vertebrate models, representing novel and exciting candidates for human NTDs. Genetic studies in NTDs have focused mainly on folate-related genes based on the finding that perinatal folic acid supplementation reduces the risk of NTDs by 60-70%. A few variants in these genes have been found to be significantly associated with an increased risk for NTDs. The candidate gene approach investigating genes involved in neurulation has failed to identify major causative genes in the etiology of NTDs. Despite this history of generally negative findings, we are achieving a rapid and impressive progress in understanding the genetic basis of NTDs, based mainly on the powerful tool of animal models.

Aberrant differentiation of the axially condensed tail bud mesenchyme in human embryos with lumbosacral myeloschisis

Development of the posterior neural tube (PNT) in human embryos is a complicated process that involves both primary and secondary neurulation. Recently, we histologically examined 20 human embryos around the stage of posterior neuropore closure and found that the axially condensed mesenchyme (AM) intervened between the neural plate/tube and the notochord in the junctional region of the primary and secondary neural tubes. The AM appeared to be incorporated into the most ventral part of the primary neural tube, and no cavity was observed in the AM. In this study, we report three cases of human embryos with myeloschisis in which the open primary neural tube and the closed secondary neural tube overlap dorsoventrally. In all three cases, part of the closed neural tube was located ventrally to the open neural tube in the lumbosacral region. The open and closed neural tubes appeared to be part of the primary and the AM-derived secondary neural tubes, respectively. Thus, these findings suggest that, in those embryos with myeloschisis, the AM may not be incorporated into the ventral part of the primary neural tube but aberrantly differentiate into the secondary neural tube containing cavities, leading to dorsoventral overlapping of the primary and secondary neural tubes. The aberrant differentiation of the AM in embryos with lumbosacral myeloschisis suggests that the AM plays some roles in normal as well as abnormal development of the human posterior neural tube.

Abnormal folate metabolism in foetuses affected by neural tube defects

Folic acid supplementation can prevent many cases of neural tube defects (NTDs), whereas suboptimal maternal folate status is a risk factor, suggesting that folate metabolism is a key determinant of susceptibility to NTDs. Despite extensive genetic analysis of folate cycle enzymes, and quantification of metabolites in maternal blood, neither the protective mechanism nor the relationship between maternal folate status and susceptibility are understood in most cases. In order to investigate potential abnormalities in folate metabolism in the embryo itself, we derived primary fibroblastic cell lines from foetuses affected by NTDs and subjected them to the dU suppression test, a sensitive metabolic test of folate metabolism. Significantly, a subset of NTD cases exhibited low scores in this test, indicative of abnormalities in folate cycling that may be causally linked to the defect. Susceptibility to NTDs may be increased by suppression of the methylation cycle, which is interlinked with the folate cycle. However, reduced efficacy in the dU suppression test was not associated with altered abundance of the methylation cycle intermediates, s-adenosylmethionine and s-adenosylhomocysteine, suggesting that a methylation cycle defect is unlikely to be responsible for the observed abnormality of folate metabolism. Genotyping of samples for known polymorphisms in genes encoding folate-associated enzymes did not reveal any correlation between specific genotypes and the observed abnormalities in folate metabolism. These data suggest that as yet unrecognized genetic variants result in embryonic abnormalities of folate cycling that may be causally related to NTDs.

The Graded Response to Sonic Hedgehog Depends on Cilia Architecture

Several studies have linked cilia and Hedgehog signaling, but the precise roles of ciliary proteins in signal transduction remain enigmatic. Here we describe a mouse mutation, hennin (hnn), that causes coupled defects in cilia structure and Sonic hedgehog (Shh) signaling. The hnn mutant cilia are short with a specific defect in the structure of the ciliary axoneme, and the hnn neural tube shows a Shh-independent expansion of the domain of motor neuron progenitors. The hnn mutation is a null allele of Arl13b, a small GTPase of the Arf/Arl family, and the Arl13b protein is localized to cilia. Double mutant analysis indicates that Gli3 repressor activity is normal in hnn embryos, but Gli activators are constitutively active at low levels. Thus, normal structure of the ciliary axoneme is required for the cell to translate different levels of Shh ligand into differential regulation of the Gli transcription factors that implement Hedgehog signals.

Health literacy and patient understanding of screening tests for aneuploidy and neural tube defects

OBJECTIVE

To determine if health literacy is associated with patient understanding of prenatal screening tests for fetal aneuploidy and neural tube defects.

METHODS

We performed a prospective observational study on a cohort of English-speaking patients receiving prenatal care in two resident-staffed ambulatory clinics. Health literacy was measured using the Rapid Estimate of Adult Literacy in Medicine-7. Understanding of the prenatal screening tests was assessed using a modified Maternal Serum Screening Knowledge Questionnaire.

RESULTS

Over an 8-month period, 125 patients were approached, and 101 (81%) consented to the study. Thirty-eight (38%) women demonstrated low health literacy. Patients with low health literacy were more likely to demonstrate inadequate understanding when compared to those with adequate health literacy (97% versus 11%, respectively; P < 0.01). Similarly, patients with < 12th grade education were more likely to have inadequate understanding when compared to patients with > 12th grade education (53% versus 30%, respectively; P = 0.02). Health literacy is a more sensitive and specific predictor of inadequate understanding than education (sensitivity 84% versus 70%, respectively, P < 0.05; specificity 98% versus 47%, respectively, P < 0.05).

CONCLUSION

Patients with low health literacy are more likely to demonstrate inadequate understanding of these prenatal screening tests than women with adequate health literacy.

Prenatal diagnosis of fetal exencephaly associated with amniotic band sequence at 17 weeks of gestation by fetal magnetic resonance imaging

We report a fetus with exencephaly diagnosed by fetal magnetic resonance imaging (MRI) at 17 weeks of gestation. Fetal ultrasound performed at 13 and 17 weeks of gestation suggested occipital encephalocele. However, the fetal MRI done at 17 weeks of gestation showed exencephaly and suggested amniotic bands as the cause. By providing early and precise information regarding the abnormality and the possible etiology, the fetal MRI enabled us to provide the couple and their families with accurate information regarding the low recurrence risk of this condition.

Planar cell polarity, ciliogenesis and neural tube defects

Cilia are microtubule-based protrusions that are found on the surface of most vertebrate cells. Long studied by cell biologists, these organelles have recently caught the attention of developmental biologists and human geneticists. In this review, I will discuss recent findings suggesting a link between cilia and the planar cell polarity signaling cascade. In particular, I will focus on how this interaction may influence the process of neural tube closure and how these results may be relevant to our understanding of common human birth defects in which neural tube closure is compromised.

Integrity of the methylation cycle is essential for mammalian neural tube closure

BACKGROUND

Closure of the cranial neural tube during embryogenesis is a crucial process in development of the brain. Failure of this event results in the severe neural tube defect (NTD) exencephaly, the developmental forerunner of anencephaly.

METHODS

The requirement for methylation cycle function in cranial neural tube closure was tested by treatment of cultured mouse embryos with cycloleucine or ethionine, inhibitors of methionine adenosyl transferase. Embryonic phenotypes were investigated by histological analysis, and immunostaining was performed for markers of proliferation and apoptosis. Methylation cycle intermediates s-adenosylmethionine and s-adenosylhomocysteine were also quantitated by tandem mass spectrometry.

RESULTS

Ethionine and cycloleucine treatments significantly reduced the ratio of abundance of s-adenosylmethionine to s-adenosylhomocysteine and are, therefore, predicted to suppress the methylation cycle. Exposure to these inhibitors during the period of cranial neurulation caused a high incidence of exencephaly, in the absence of generalized toxicity, growth retardation, or developmental delay. Reduced neuroepithelial thickness and reduced density of cranial mesenchyme were detected in ethionine-treated but not cycloleucine-treated embryos that developed exencephaly. Reduced mesenchymal density is a potential cause of ethionine-induced exencephaly, although we could not detect a causative alteration in proliferation or apoptosis prior to failure of neural tube closure.

CONCLUSIONS

Adequate functioning of the methylation cycle is essential for cranial neural tube closure in the mouse, suggesting that suppression of the methylation cycle could also increase the risk of human NTDs. We hypothesize that inhibition of the methylation cycle causes NTDs due to disruption of crucial reactions involving methylation of DNA, proteins or other biomolecules.

Tissue, cellular and sub-cellular localization of the Vangl2 protein during embryonic development: effect of the Lp mutation

Loop-tail (Lp) mice show a very severe neural tube defect, craniorachischisis, which is caused by mis-sense mutations in the Vangl2 gene. The membrane protein Vangl2 belongs to a highly conserved group of proteins that regulate planar polarity in certain epithelia, and that are also important for convergent extension movements during gastrulation and neurulation. A specific anti-Vangl2 antiserum was produced and used to examine the tissue, cell type, and sub-cellular localization of Vangl2 during embryogenesis. Vangl2 protein is expressed at high levels in the neural tube and shows a dynamic expression profile during neurulation. After neural tube closure, robust Vangl2 staining is detected in several neural and neurosensory tissues, including cerebral cortex, dorsal root ganglia, olfactory epithelium, retina, mechanosensory hair cells of the cochlea, and optic nerve. Vangl2 is also expressed during organogenesis in a number of tubular epithelia, including the bronchial tree, intestinal crypt/villus axis, and renal tubular segments derived from ureteric bud and from metanephric mesenchyme. Examination of Vangl2 localization in the neural tubes and cochleas of the normal and Lp/Lp embryos shows disruption of normal membrane localization of Vangl2 in independent alleles at Lp (Lp, Lp(m1Jus)) as well as overall decrease in the expression level.

The chicken talpid3 gene encodes a novel protein essential for Hedgehog signaling

Talpid3 is a classical chicken mutant with abnormal limb patterning and malformations in other regions of the embryo known to depend on Hedgehog signaling. We combined the ease of manipulating chicken embryos with emerging knowledge of the chicken genome to reveal directly the basis of defective Hedgehog signal transduction in talpid3 embryos and to identify the talpid3 gene. We show in several regions of the embryo that the talpid3 phenotype is completely ligand independent and demonstrate for the first time that talpid3 is absolutely required for the function of both Gli repressor and activator in the intracellular Hedgehog pathway. We map the talpid3 locus to chromosome 5 and find a frameshift mutation in a KIAA0586 ortholog (ENSGALG00000012025), a gene not previously attributed with any known function. We show a direct causal link between KIAA0586 and the mutant phenotype by rescue experiments. KIAA0586 encodes a novel protein, apparently specific to vertebrates, that localizes to the cytoplasm. We show that Gli3 processing is abnormal in talpid3 mutant cells but that Gli3 can still translocate to the nucleus. These results suggest that the talpid3 protein operates in the cytoplasm to regulate the activity of both Gli repressor and activator proteins.

Extremely high prevalence of neural tube defects in a 4-county area in Shanxi Province, China

BACKGROUND

In the past, northern China's Shanxi Province has reported the highest incidence of neural tube defects (NTDs) in the world. However, little is known about the epidemiology of NTDs in this area in recent years.

METHODS

Data were collected from a population-based birth defects surveillance system in 4 counties that captures information on all live births, stillbirths of at least 20 weeks' gestation, and pregnancy terminations at any gestational age resulting from prenatal diagnosis of a birth defect. We also surveyed mothers of NTD case patients to determine their use of folic acid before and during early pregnancy.

RESULTS

During 2003, 160 NTD cases were identified among 11,534 births (NTD birth prevalence = 138.7/10,000 births). The rates of anencephaly, spina bifida and encephalocele were 65.9, 58.1, and 14.7 per 10,000, respectively, and a female predominance was observed among anencephaly cases (male-to-female relative risk [RR], 0.49; 95% confidence interval [CI], 0.30-0.79), but not among spina bifida (RR, 0.90; 95% CI, 0.55-1.45) and encephalocele (RR, 1.03; 95% CI, 0.40-2.69) cases. The percentages of pregnancy termination following prenatal diagnosis of anencephaly, spina bifida, and encephalocele were 50%, 41.8%, and 35.3%, respectively. NTD birth prevalence tended to be higher among mothers aged <20 or > or =30 years (P = .06) and was markedly associated with lower levels of maternal education (P < .001). Among 143 NTD mothers, only 6 (4.2%) used folic acid supplements during the periconceptional period.

CONCLUSIONS

The NTD birth prevalence rate in the study area is among the highest worldwide. Folic acid deficiency may be one important risk factor.

Effect of maternal exposure to homocystine on sodium valproate-induced neural tube defects in the mouse embryos

BACKGROUND

Neural tube defects (NTD) are mainly of multifactorial origin. Maternal treatment with valproic acid (VPA) during pregnancy induces NTD in susceptible fetuses. Elevated levels of homocysteine are observed in pregnancies with NTD. The mechanism by which homocysteine might cause NTD is unknown.

AIM OF THE STUDY

The aim of this study was to determine if homocystine would augment VPA-induced exencephaly in an experimental model.

METHODS

Groups of mice were injected (IP) on gestational day 8 (GD) with a single dose of 75 mg/kg of L: -Homocystine (HC) or a proportionate volume of saline, followed by a single dose of 600 mg/kg of VPA or an equal volume of saline. In a second experiment, mice were treated with a daily dose of 75 mg/kg of HC or an equal volume of saline (IP) from GD 5 and continued through GD 10. These animals had a single exposure to 600 mg/kg of VPA or saline (IP) on GD 8. All animals were killed by cervical dislocation on GD 18. Plasma homocysteine, folate and vitamin B12 were determined on GD 8 and GD 10 from single and multiple dose groups of mice, respectively, from additional experiments.

RESULTS

The VPA and HC+VPA induced significantly higher rates of embryonic resorption and intrauterine growth retardation (IUGR) than HC or saline alone. HC + VPA groups had significantly more numerous fetuses with severe IUGR than HC alone or VPA alone groups. Both single and multiple doses of HC augmented VPA-induced reduction in fetal body weight. Successive doses of HC did not augment the rate of IUGR more significantly than a single dose of HC. Incidence of exencephaly was significantly enhanced in the HC + VPA groups compared to that in the HC or VPA alone groups. HC alone was not teratogenic. Plasma homocysteine levels increased several fold both in HC and HC + VPA groups and the increase was not particularly more marked in multiple dose groups than in the single dose groups. VPA did not elevate homocysteine concentration. Both FA and vitamin B12 concentrations were reduced by VPA, HC and HC + VPA, but HC and VPA when combined did not produce an additive effect on vitamin levels.

CONCLUSION

These data indicate that HC and VPA interact in neurulation stage embryos, affect fundamental processes of closure of the neural tube and lead to enhanced incidence of NTD.

Excess methionine suppresses the methylation cycle and inhibits neural tube closure in mouse embryos

Suppression of one-carbon metabolism or insufficient methionine intake are suggested to increase risk of neural tube defects (NTD). Here, exogenous methionine unexpectedly caused frequent NTD in cultured mouse embryos. NTD were associated with reduced cranial mesenchyme cell density, which may result from a preceding reduction in proliferation. The abundance ratio of S-adenosylmethionine to S-adenosylhomocysteine was also decreased in treated embryos, suggesting methylation reactions may be suppressed. Such an effect is potentially causative as NTD were also observed when DNA methylation was specifically inhibited. Thus, reduced cranial mesenchyme density and impairment of critical methylation reactions may contribute to development of methionine-induced NTD.

Bromochloro-haloacetic acids: Effects on mouse embryos in vitro and QSAR considerations

The haloacetic acids (HAA) are a family of chemicals that are drinking water disinfection by-products. We previously reported that haloacetic acids, including several bromo- and chloro-HAAs, alter embryonic development when mouse conceptuses are directly exposed to these xenobiotics in whole embryo culture. Craniofacial dysmorphogenesis was observed in exposed embryos and a quantitative structure activity relationship (QSAR) for induction of cranial neural tube dysmorphogenesis was established for a series of 10 HAAs, which also included fluoro- and iodo-HAA representatives. In the current study, we evaluate the effects of exposing neurulation staged (3-6 somite pairs) CD-1 mouse conceptuses to bromochloro- (BCA), dibromochloro- (DBCA) and bromodichloro-acetic (BDCA) acids in whole embryo culture at concentrations ranging from 50 to 2500 microM. Morphological development was assessed after a 26 h exposure period. Exposure of conceptuses to these HAAs produced dysmorphogenesis, including prosencephalic and pharyngeal arch hypoplasia as well as eye and heart tube abnormalities. Benchmark concentrations for induction of neural tube dysmorphogenesis were 63, 500 and 536 microM for BCA, DBCA and BDCA, respectively. Our previously developed HAA QSAR accurately predicted placement of these three chemicals in the larger context of the previously tested di- and tri-HAAs, also correctly predicting that BCA would be more potent than DBCA and BDCA, and that the latter two HAAs would be near equi-potent. This study describes the concentration-dependent induction of dysmorphogenesis in whole embryo culture by three mixed chloro/bromo-HAAs and demonstrates the ability of the HAA QSAR to predict relative potencies within this family of xenobiotics.

Neurulation in the cranial region--normal and abnormal

Cranial neurulation is the embryonic process responsible for formation of the brain primordium. In the mouse embryo, cranial neurulation is a piecemeal process with several initiation sites and two neuropores. Variation in the pattern of cranial neurulation occurs in different mouse strains, and a simpler version of this morphogenetic scheme has been described in human embryos. Exencephaly is more common in females than in males, an unexplained phenomenon seen in both mice and humans. As the cranial neural tube closes, a critical morphogenetic event is the formation of dorsolateral bending points near the neural fold tips, which enables subsequent midline fusion of the neural folds. Many mutant and gene-targeted mouse strains develop cranial neural tube defects, and analysis of the underlying molecular defects identifies several requirements for normal dorsolateral bending. These include a functional actin cytoskeleton, emigration of the cranial neural crest, spatio-temporally regulated apoptosis, and a balance between cell proliferation and the onset of neuronal differentiation. A small number of mouse mutants exhibit craniorachischisis, a combined brain and spine neurulation defect. Recent studies show that disturbance of a single molecular signalling cascade, the planar cell polarity pathway, is implicated in mutants with this defect.

The mouse Ovol2 gene is required for cranial neural tube development

The Ovo gene family encodes a group of evolutionarily conserved transcription factors and includes members that reside downstream of key developmental signaling pathways such as Wg/Wnt and BMP/TGF-beta. In the current study, we explore the function of Ovol2, one of three Ovo paralogues in mice. We report that Ovol2 is expressed during early-mid embryogenesis, particularly in the inner cell mass at E3.5, in epiblast at E6.5, and at later stages in ectodermally derived tissues such as the rostral surface (epidermal) ectoderm. Embryos in which Ovol2 is ablated exhibit lethality by E10.5, prior to which they display severe defects including an open cranial neural tube. The neural defects are associated with improper Shh expression in the underlying rostral axial mesoderm and localized changes of neural marker expression along the dorsoventral axis, as well as with expanded cranial neural tissue and reduced cranial surface ectoderm culminating in a lateral shift of the neuroectoderm/surface ectoderm border. We propose that these defects reflect the involvement of Ovol2 in independent processes such as regionalized gene expression and neural/non-neural ectodermal patterning. Additionally, we present evidence that Ovol2 is required for efficient migration and survival of neural crest cells that arise at the neuroectoderm/surface ectoderm border, but not for their initial formation. Collectively, our studies indicate that Ovol2 is a key regulator of neural development and reveal a previously unexplored role for Ovo genes in mammalian embryogenesis.