Tube Defects In Humans Research Articles

Mycotoxins in Cereal-Based Products and Their Impacts on the Health of Humans, Livestock Animals and Pets.

Cereal grains are the most important food staples for human beings and livestock animals. They can be processed into various types of food and feed products such as bread, pasta, breakfast cereals, cake, snacks, beer, complete feed, and pet foods. However, cereal grains are vulnerable to the contamination of soil microorganisms, particularly molds. The toxigenic fungi/molds not only cause quality deterioration and grain loss, but also produce toxic secondary metabolites, mycotoxins, which can cause acute toxicity, death, and chronic diseases such as cancer, immunity suppression, growth impairment, and neural tube defects in humans, livestock animals and pets. To protect human beings and animals from these health risks, many countries have established/adopted regulations to limit exposure to mycotoxins. The purpose of this review is to update the evidence regarding the occurrence and co-occurrence of mycotoxins in cereal grains and cereal-derived food and feed products and their health impacts on human beings, livestock animals and pets. The effort for safe food and feed supplies including prevention technologies, detoxification technologies/methods and up-to-date regulation limits of frequently detected mycotoxins in cereal grains for food and feed in major cereal-producing countries are also provided. Some important areas worthy of further investigation are proposed.

A quest for genetic causes underlying signaling pathways associated with neural tube defects.

Neural tube defects (NTDs) are serious congenital deformities of the nervous system that occur owing to the failure of normal neural tube closures. Genetic and non-genetic factors contribute to the etiology of neural tube defects in humans, indicating the role of gene-gene and gene-environment interaction in the occurrence and recurrence risk of neural tube defects. Several lines of genetic studies on humans and animals demonstrated the role of aberrant genes in the developmental risk of neural tube defects and also provided an understanding of the cellular and morphological programs that occur during embryonic development. Other studies observed the effects of folate and supplementation of folic acid on neural tube defects. Hence, here we review what is known to date regarding altered genes associated with specific signaling pathways resulting in NTDs, as well as highlight the role of various genetic, and non-genetic factors and their interactions that contribute to NTDs. Additionally, we also shine a light on the role of folate and cell adhesion molecules (CAMs) in neural tube defects.

Paternal arsenic exposure increases risk of myelomeningocele among offspring in a highly-exposed population

Background: Neural tube defects, severe birth defects that occur when the neural plate fails to close in early gestation, continue to be a pressing public health concern, despite advances in prevention from folic acid-based strategies. Arsenic, a chemical naturally occurring in soils and drinking water, has been shown to induce neural tube defects in animal models and could contribute to neural tube defects in humans. We investigated the relationship between parental arsenic exposure and risk of myelomeningocele, a common and severe form of neural tube defect, in a case control study in Bangladesh. We also explored the interaction between arsenic levels and maternal serum folate. Methods: We analyzed arsenic in maternal and paternal toenail samples using inductively coupled plasma mass spectrometry. A total of 275 participants (153 cases and 122 controls) were included in the analysis. Results: On average, fathers of cases had higher levels of arsenic in toenails than fathers of controls. Maternal toenail arsenic levels were not significantly related to case status in the main effect model. In the paternal model, a 1-unit increase in the natural logarithm of toenail arsenic was significantly associated with 75% greater odds of being a case (adjusted odds ratios: 1.75) compared to being a control after adjusting for maternal serum folate level, parental age, child age, birth facility, and child sex. Results did not suggest an interaction between paternal arsenic and maternal serum folate. Conclusions: The findings from this study provide novel insight into the role of arsenic in neural tube defect risk in humans and add to the growing body of literature of the influence of paternal environmental factors on child health outcomes.

Differentiation of neural rosettes from human pluripotent stem cells in vitro is sequentially regulated on a molecular level and accomplished by the mechanism reminiscent of secondary neurulation

Development of neural tube has been extensively modeled in vitro using human pluripotent stem cells (hPSCs) that are able to form radially organized cellular structures called neural rosettes. While a great amount of research has been done using neural rosettes, studies have only inadequately addressed how rosettes are formed and what the molecular mechanisms and pathways involved in their formation are. Here we address this question by detailed analysis of the expression of pluripotency and differentiation-associated proteins during the early onset of differentiation of hPSCs towards neural rosettes. Additionally, we show that the BMP signaling is likely contributing to the formation of the complex cluster of neural rosettes and its inhibition leads to the altered expression of PAX6, SOX2 and SOX1 proteins and the rosette morphology. Finally, we provide evidence that the mechanism of neural rosettes formation in vitro is reminiscent of the process of secondary neurulation rather than that of primary neurulation in vivo. Since secondary neurulation is a largely unexplored process, its understanding will ultimately assist the development of methods to prevent caudal neural tube defects in humans.

Does arsenic increase the risk of neural tube defects among a highly exposed population? A new case–control study in Bangladesh

Neural tube defects are debilitating birth defects that occur when the developing neural plate fails to close in early gestation. Arsenic induces neural tube defects in animal models, but whether environmental arsenic exposure increases risk of neural tube defects in humans is unknown. We describe a new case-control study in Bangladesh, a country currently experiencing an epidemic of arsenic poisoning through contaminated drinking water. We plan to understand how arsenic influences risk of neural tube defects in humans through mechanisms that include disruption of maternal glucose and folate metabolism, as well as epigenetic effects. We also investigate whether sweat chloride concentration, a potential new biomarker for arsenic toxicity, can be used to identify women at higher risk for having a child affected by neural tube defect. We will collect dural tissue from cases, obtained at the time of surgical closure of the defect, and believe investigation of these samples will provide insight into the epigenetic mechanisms by which prenatal arsenic exposure affects the developing nervous system. These studies explore mechanisms by which arsenic may increase risk of neural tube defects in humans and use a unique population with high arsenic exposure to test hypotheses. If successful, these studies may assist countries with high arsenic exposure such as Bangladesh to identify populations at high risk of neural tube defects, as well as direct development of novel screening strategies for maternal risk.Birth Defects Research 109:92-98, 2017.© 2016 The Authors Birth Defects Research Published by Wiley Periodicals, Inc.

Mutations in the Motile Cilia Gene DNAAF1 Are Associated with Neural Tube Defects in Humans.

Neural tube defects (NTDs) are severe malformations of the central nervous system caused by complex genetic and environmental factors. Among genes involved in NTD, cilia-related genes have been well defined and found to be essential for the completion of neural tube closure (NTC). We have carried out next-generation sequencing on target genes in 373 NTDs and 222 healthy controls, and discovered eight disease-specific rare mutations in cilia-related gene DNAAF1. DNAAF1 plays a central role in cytoplasmic preassembly of distinct dynein-arm complexes, and is expressed in some key tissues involved in neural system development, such as neural tube, floor plate, embryonic node, and brain ependyma epithelial cells in zebrafish and mouse. Therefore, we evaluated the expression and functions of mutations in DNAAF1 in transfected cells to analyze the potential correlation of these mutants to NTDs in humans. One rare frameshift mutation (p.Gln341Argfs*10) resulted in significantly diminished DNAAF1 protein expression, compared to the wild type. Another mutation, p.Lys231Gln, disrupted cytoplasmic preassembly of the dynein-arm complexes in cellular assay. Furthermore, results from NanoString assay on mRNA from NTD samples indicated that DNAAF1 mutants altered the expression level of NTC-related genes. Altogether, these findings suggest that the rare mutations in DNAAF1 may contribute to the susceptibility for NTDs in humans.

Role of the planar cell polarity gene Protein tyrosine kinase 7 in neural tube defects in humans.

Neural tube defects (NTDs) are among the most common congenital defects affecting approximately 1 in 1000 live births in North America. Their etiology is complex including environmental and genetic factors. Defects in the planar cell polarity (PCP) signaling pathway have been strongly associated with NTDs in animal models and human cohorts. Protein tyrosine kinase 7 (Ptk7) was shown to cause a very severe form of NTDs called craniorachischisis in a mouse model and genetically interacts with a core PCP member Vangl2 where double heterozygotes suffer from spina bifida. In this study, we examined the role of PTK7 in human NTDs to determine whether variants at this gene predispose to these defects. We sequenced the coding region and the exon-intron junctions of PTK7 in a cohort of 473 patients affected with various forms of open and closed NTDs. Novel and rare variants(<1%) were genotyped in a cohort of 473 individuals. Their pathogenic effect was predicted in silico and functionally in an overexpression assay in a well-established zebrafish model. We identified in our cohort 6 rare variants, 3 of which were absent in public databases. One variant, p.Gly348Ser, acted as a hypermorph when overexpressed in the zebrafish model. We detected potentially pathogenic PTK7 variants in 1.1% of our NTD cohort. Our findings implicate PTK7 as a risk factor for NTDs and provide additional evidence for a pathogenic role of PCP signaling in these malformations.

Arsenic is associated with reduced effect of folic acid in myelomeningocele prevention: a case control study in Bangladesh.

BackgroundArsenic induces neural tube defects in several animal models, but its potential to cause neural tube defects in humans is unknown. Our objective was to investigate the associations between maternal arsenic exposure, periconceptional folic acid supplementation, and risk of posterior neural tube defect (myelomeningocele) among a highly exposed population in rural Bangladesh.MethodsWe performed a case–control study that recruited physician-confirmed cases from community health clinics served by Dhaka Community Hospital in Bangladesh, as well as local health facilities that treat children with myelomeningocele. Controls were selected from pregnancy registries in the same areas. Maternal arsenic exposure was estimated from drinking water samples taken from wells used during the first trimester of pregnancy. Periconceptional folic acid use was ascertained by self-report, and maternal folate status was further assessed by plasma folate levels measured at the time of the study visit.ResultsFifty-seven cases of myelomeningocele were identified along with 55 controls. A significant interaction was observed between drinking water inorganic arsenic and periconceptional folic acid use. As drinking water inorganic arsenic concentrations increased from 1 to 25 μg/L, the estimated protective effect of folic acid use declined (OR 0.22 to 1.03), and was not protective at higher concentrations of arsenic. No main effect of arsenic exposure on myelomeningocele risk was identified.ConclusionsOur study found a significant interaction between drinking water inorganic arsenic concentration from wells used during the first trimester of pregnancy and reported intake of periconceptional folic acid supplements. Results suggest that environmental arsenic exposure reduces the effectiveness of folic acid supplementation in preventing myelomeningocele.

Independent mutations at Arg181 and Arg274 of Vangl proteins that are associated with neural tube defects in humans decrease protein stability and impair membrane targeting.

In vertebrates, Vangl proteins play important roles during embryogenesis, including establishing planar polarity and coordinating convergent extension movements. In mice, homozygosity for mutations in the Vangl1 and Vangl2 genes or combined heterozygosity for Vangl1/Vangl2 mutations causes the very severe neural tube defect (NTD) craniorachischisis. Recently, a number of patient-specific VANGL1 and VANGL2 protein mutations have been identified in familial and sporadic cases of mild and severe forms of NTDs. The biochemical nature of pathological effects in these mutations remains unknown. Of interest are two arginine residues, R181 and R274, that are highly conserved in Vangl protein homologues and found to be independently mutated in VANGL1 (R181Q and R274Q) and VANGL2 (R177H and R270H) in human cases of NTDs. The cellular and biochemical properties of R181Q and R274Q were established in transfected MDCK kidney epithelial cells and compared to those of wild-type (WT) Vangl1. Compared to that of WT, these mutations displayed impaired targeting to the plasma membrane and were instead detected in an intracellular endomembrane compartment that was positive for the endoplasmic reticulum. R181Q and R274Q showed impaired stability with significant reductions in measured half-lives from >20 h for WT protein to 9 and 5 h, respectively. These mutations have a cellular and biochemical phenotype that is indistinguishable from that of Vangl mutations known to cause craniorachichisis in mice (Lp). These results strongly suggest that R181 and R274 play critical roles in Vangl protein function and that their mutations cause neural tube defects in humans.

Genome-Wide Association Mapping in Dogs Enables Identification of the Homeobox Gene, NKX2-8, as a Genetic Component of Neural Tube Defects in Humans

Neural tube defects (NTDs) is a general term for central nervous system malformations secondary to a failure of closure or development of the neural tube. The resulting pathologies may involve the brain, spinal cord and/or vertebral column, in addition to associated structures such as soft tissue or skin. The condition is reported among the more common birth defects in humans, leading to significant infant morbidity and mortality. The etiology remains poorly understood but genetic, nutritional, environmental factors, or a combination of these, are known to play a role in the development of NTDs. The variable conditions associated with NTDs occur naturally in dogs, and have been previously reported in the Weimaraner breed. Taking advantage of the strong linkage-disequilibrium within dog breeds we performed genome-wide association analysis and mapped a genomic region for spinal dysraphism, a presumed NTD, using 4 affected and 96 unaffected Weimaraners. The associated region on canine chromosome 8 (pgenome = 3.0×10−5), after 100,000 permutations, encodes 18 genes, including NKX2-8, a homeobox gene which is expressed in the developing neural tube. Sequencing NKX2-8 in affected Weimaraners revealed a G to AA frameshift mutation within exon 2 of the gene, resulting in a premature stop codon that is predicted to produce a truncated protein. The exons of NKX2-8 were sequenced in human patients with spina bifida and rare variants (rs61755040 and rs10135525) were found to be significantly over-represented (p = 0.036). This is the first documentation of a potential role for NKX2-8 in the etiology of NTDs, made possible by investigating the molecular basis of naturally occurring mutations in dogs.

Is LMNB1 a susceptibility gene for neural tube defects in humans?

BACKGROUNDLamins are intermediate filament proteins that form a major component of the nuclear lamina, a protein complex at the surface of the inner nuclear membrane. Numerous clinically diverse conditions, termed laminopathies, have been found to result from mutation of LMNA. In contrast, coding or loss of function mutations of LMNB1, encoding lamin B1, have not been identified in human disease. In mice, polymorphism in Lmnb1 has been shown to modify risk of neural tube defects (NTDs), malformations of the central nervous system that result from incomplete closure of the neural folds.METHODSMutation analysis by DNA sequencing was performed on all exons of LMNB1 in 239 samples from patients with NTDs from the United Kingdom, Sweden, and United States. Possible functional effects of missense variants were analyzed by bioinformatics prediction and fluorescence in photobleaching.RESULTSIn NTD patients, we identified two unique missense variants that were predicted to disrupt protein structure/function and represent putative contributory mutations. Fluorescence loss in photobleaching analysis showed that the A436T variant compromised stability of lamin B1 interaction within the lamina.CONCLUSIONThe genetic basis of human NTDs appears highly heterogenous with possible involvement of multiple predisposing genes. We hypothesize that rare variants of LMNB1 may contribute to susceptibility to NTDs. Birth Defects Research (Part A) 97:398–402, 2013. © 2013 Wiley Periodicals, Inc.

Lae1 regulates expression of multiple secondary metabolite gene clusters in Fusarium verticillioides

The filamentous fungus Fusarium verticillioides can cause disease of maize and is capable of producing fumonisins, a family of toxic secondary metabolites linked to esophageal cancer and neural tube defects in humans and lung edema in swine and leukoencephalomalacia in equines. The expression of fumonisin biosynthetic genes is influenced by broad-domain transcription factors (global regulators) and Fum21, a pathway-specific transcription factor. LaeA is a global regulator that in Aspergillus nidulans, affects the expression of multiple secondary metabolite gene clusters by modifying heterochromatin structure. Here, we employed gene deletion analysis to assess the effect of loss of a F. verticillioides laeA orthologue, LAE1, on genome-wide gene expression and secondary metabolite production. Loss of Lae1 resulted in reduced expression of gene clusters responsible for synthesis of the secondary metabolites bikaverin, fumonisins, fusaric acid and fusarins as well as two clusters for which the corresponding secondary metabolite is unknown. Analysis of secondary metabolites revealed that, in contrast to a previously described Fusarium fujikuroi lae1 mutant, bikaverin production is reduced. Fumonisin production is unchanged in the F. verticillioides lae1 mutant. Complementation of the F. verticillioides mutant resulted in increased fumonisin production.

Mutations in the planar cell polarity gene, Fuzzy, are associated with neural tube defects in humans

Neural tube defects (NTDs) are a heterogeneous group of common severe congenital anomalies which affect 1-2 infants per 1000 births. Most genetic and/or environmental factors that contribute to the pathogenesis of human NTDs are unknown. Recently, however, pathogenic mutations of VANGL1 and VANGL2 genes have been associated with some cases of human NTDs. Vangl genes encode proteins of the planar cell polarity (PCP) pathway that regulates cell behavior during early stages of neural tube formation. Homozygous disruption of PCP genes in mice results in a spectrum of NTDs, including defects that affect the entire neural axis (craniorachischisis), cranial NTDs (exencephaly) and spina bifida. In this paper, we report the dynamic expression of another PCP gene, Fuzzy, during neural tube formation in mice. We also identify non-synonymous Fuzzy amino acid substitutions in some patients with NTDs and demonstrate that several of these Fuzzy mutations affect formation of primary cilia and ciliary length or affect directional cell movement. Since Fuzzy knockout mice exhibit both NTDs and defective primary cilia and Fuzzy is expressed in the emerging neural tube, we propose that mutations in Fuzzy may account for a subset of NTDs in humans.

Determination of fumonisins in maize by HPLC with ultraviolet detection of o-phthaldialdehyde derivatives

Fumonisins are mycotoxins that are produced by various Fusarium species and occur naturally in maize and maize-based foods. Fumonisins are carcinogenic, causing liver cancer in rats, and are associated with oesophageal cancer and neural tube defects in humans. Analytical methods for individual fumonisin analogues in maize rely on reversed-phase high-performance liquid chromatographic (HPLC) separation after suitable extraction and clean-up. As fumonisins lack a useful chromophore or fluorophore, HPLC detection is achieved by suitable derivatization and sensitive, specific fluorescence detection. A widely used and validated method involves extract clean-up on strong anion exchange solid phase extraction cartridges and pre-column derivatization with o-phthaldialdehyde (OPA). However, many laboratories requiring infrequent fumonisin analysis are only equipped with HPLC with ultraviolet (UV) detection. A HPLC system equipped with both UV and fluorescence detectors connected in series was used to determine the extent to which UV offers an alternative to fluorescence detection in the above analytical method. Comparison of the detection systems using fumonisin standards indicated that fluorescence is about 20-times more sensitive than UV. Analysis of maize samples with differing fumonisin contamination levels indicated that, at fumonisin B1 levels above 1,000µg/kg, the two detection systems were comparable and gave repeatabilities equal or less than 10% on six replicate analyses. Although a sensitive fumonisin analysis requires fluorescence detection, UV may offer an alternative in certain circumstances.

Ascorbic acid reverses valproic acid-induced inhibition of hoxa2 and maintains glutathione homeostasis in mouse embryos in culture.

Valproic acid (VPA) has been shown to cause neural tube defects in humans and mice, but its mechanism of action has not been elucidated. We hypothesize that alterations in embryonic antioxidant status and Hoxa2 gene expression play an important role in VPA-induced teratogenesis. A whole embryo culture system was applied to explore the effects of VPA on total glutathione, on glutathione in its oxidized (GSSG) and reduced (GSH) forms [GSSG/GSH ratio] and on Hoxa2 expression in cultured CD-1 mouse embryos during their critical period of organogenesis. Our results show that VPA can (1) induce embryo malformations including neural tube defects, abnormal flexion, yolk sac circulation defects, somite defects, and craniofacial deformities such as fusion of the first and second arches, and (2) alter glutathione homeostasis of embryos through an increase in embryonic GSSG/GSH ratio and a decrease in total GSH content in embryos. Western blot analysis and quantitative real-time RT-PCR show that VPA can inhibit Hoxa2 expression in cultured embryos at both the protein and mRNA level, respectively. The presence of ascorbic acid in the culture media was effective in protecting embryos against oxidative stress induced by VPA and prevented VPA-induced inhibition of Hoxa2 gene expression. Hoxa2 null mutant embryos do not exhibit altered glutathione homeostasis, indicating that inhibition of Hoxa2 is downstream of VPA-induced oxidative stress. These results are first to suggest VPA may, in part, exert its teratogenicity through alteration of the embryonic antioxidant status and inhibition of Hoxa2 gene expression and that ascorbic acid can protect embryos from VPA-induced oxidative stress.

A PLP-Dependent Polyketide Chain Releasing Mechanism in the Biosynthesis of Mycotoxin Fumonisins inFusarium verticillioides

Fumonisins are polyketide-derived mycotoxins produced by several plant pathogenic fungi. The toxins cause several fatal diseases in domestic animals and are associated with esophageal cancer and neural tube defects in humans. Fumonisins contain a highly reduced, acyclic 18-carbon chain, which is synthesized by an iterative polyketide synthase (PKS). This PKS does not contain a thioesterase or cyclase domain that is found in other PKSs for the release of the covalently linked polyketide chain. In this study, we expressed the acyl carrier protein (ACP) of FUM1 and in vitro loaded acyl chains to the ACP from acyl-CoA using a promiscuous 4'-phosphopantetheinyl transferase. We then expressed FUM8, which is homologous to 2-oxoamine synthase genes, in yeast and showed that the enzyme is able to offload the acyl chains from ACP. Products resulted from the decarboxylative condensation between l-alanine and acyl-S-ACP were detected by GC-MS. The enzyme activity was dependent on pyridoxal 5'-phosphate (PLP), and C18-S-ACP was the preferred substrate. The results revealed a novel polyketide chain-releasing mechanism, in which a PLP-dependent enzyme catalyzes the termination and offloading of the polyketide chain as well as the introduction of a new carbon-carbon bond and an amino group to the chain. The mechanism is fundamentally different from the thioesterase/cyclase-catalyzed polyketide chain release found in bacterial and other fungal polyketide biosyntheses.

Biosynthesis of sphinganine-analog mycotoxins

Sphinganine-analog mycotoxins (SAMT) are polyketide-derived natural products produced by a number of plant pathogenic fungi and are among the most economically important mycotoxins. The toxins are structurally similar to sphinganine, a key intermediate in the biosynthesis of ceramides and sphingolipids, and competitive inhibitors for ceramide synthase. The inhibition of ceramide and sphingolipid biosynthesis is associated with several fatal diseases in domestic animals and esophageal cancer and neural tube defects in humans. SAMT contains a highly reduced, acyclic polyketide carbon backbone, which is assembled by a single module polyketide synthase. The biosynthesis of SAMT involves a unique polyketide chain-releasing mechanism, in which a pyridoxal 5'-phosphate-dependent enzyme catalyzes the termination, offloading and elongation of the polyketide chain. This leads to the introduction of a new carbon-carbon bond and an amino group to the polyketide chain. The mechanism is fundamentally different from the thioesterase/cyclase-catalyzed polyketide chain releasing found in bacterial and other fungal polyketide biosynthesis. Genetic data suggest that the ketosynthase domain of the polyketide synthase and the chain-releasing enzyme are important for controlling the final product structure. In addition, several post-polyketide modifications have to take place before SAMT become mature toxins.

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 variants in ZIC1, ZIC2, and ZIC3 are not major risk factors for neural tube defects in humans.

Neural tube defects (NTD) are congenital malformations arising from incomplete neural tube closure during early embryogenesis. Most NTD in humans show complex inheritance patterns, with both genetic and environmental factors involved in the etiology of this malformation. More than 120 mouse models for human NTD exist. NTD have been observed in mice deficient for the Zic family genes, Zic1, Zic2, and Zic3. We performed mutation analysis in the human orthologs of these genes using DNA material from a large panel of NTD patients. In ZIC2 we identified a deletion of one codon that encodes an alanine residue located in the amino terminal alanine stretch of the protein. The deletion was present in one patient, but not in 364 controls. That may suggest a role-albeit small-of this variant in the etiology of NTD in humans. Transmission disequilibrium testing of a frequent polymorphism in the ZIC2 gene (1059C > T, H353H) in parent-spina bifida aperta child triads showed no association with NTD. One silent polymorphism (858G > A, V286V) of unknown significance was identified in ZIC3. Neither mutations nor polymorphisms were found in the coding region or flanking sequences of ZIC1. Our data indicate that ZIC1, ZIC2, and ZIC3 are not major risk factors for NTD in humans.

Transcobalamin and methionine synthase reductase mutated polymorphisms aggravate the risk of neural tube defects in humans

The pathogenic mechanism of neural tube defects may involve genetic polymorphisms and nutritional factors related to homocysteine metabolism. We evaluated the association of polymorphisms of three genes affecting vitamin B12-dependent remethylation of homocysteine, transcobalamin ( TC), methionine synthase ( MTR) and MTR reductase ( MTRR), combined or not with methylenetetrahydrofolate reductase ( MTHFR), with the risk of having neural tube defect in 40 children with spina bifida and 58 matched controls from South Italy. MTR 2756 AG/GG, TC 777 CG/GG /MTHFR 677 CC and MTRR 66 GG /MTHFR 677 CC genotypes increased the risk with odds ratios of 2.6 ( P=0.046), 2.4 ( P=0.028) and 4.5 ( P=0.023), respectively. In contrast, MTHFR 677 TT was protective (odds ratio=0.11, P=0.009). In conclusion, genetic determinants affecting the cellular availability or MTRR-dependent reduction of B12 may increase the risk of spina bifida.