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Risk factors for neural tube defects: associations between uncoupling protein 2 polymorphisms and spina bifida.

BACKGROUND: Polymorphisms in the mitochondrial membrane transporter gene UCP2 are capable of affecting energy metabolism, body weight regulation, and possibly preventing the buildup of reactive oxygen species, all factors that could contribute to neural tube defect risk through maternal obesity and diabetes. METHODS: Genomic DNA was extracted from newborn screening blood spots obtained from infants with spina bifida and nonmalformed control infants. Genotype frequencies of two genetic variants in the UCP2 gene, an amino acid substitution of valine for alanine at codon 55 in exon 4, and a 45-base pair insertion/deletion in the 3' untranslated region of exon 8,were determined by restriction enzyme digestion of PCR amplification products. RESULTS: We found the frequency of the 3' untranslated region deletion homozygous genotype (256/256) as well as the A55V homozygous (Val/Val) genotype to be higher in SB infants than in controls (odds ratio [OR], 3.1; 95% confidence interval [CI], 0.9-10.4 and OR = 2.0; 95% CI = 0.3-11.1, respectively). Additionally, the frequency of the combined homozygous 256/256,+ / + genotype was higher in cases and resulted in more than a threefold higher spina bifida risk (OR = 3.6; 95% CI = 1.0-13.1). CONCLUSIONS: These data are the first to suggest that polymorphisms in the UCP2 gene may be genetic risk factors of spina bifida.

California↗

Effect of gestational age on screening for neural-tube defects by maternal plasma-A.F.P. measurement.

Maternal plasma or serum alpha-feto-protein (A.F.P.) concentrations were measured once between 8 and 22 weeks of gestation in each of sixty-two pregnancies which resulted in an infant with a neural-tube defect. Between 13 and 22 weeks of pregnancy twenty-two of the forty-one cases tested (54%) had A.F.P. values greater than three times the median value for unaffected pregnancies (which is equivalent to the 97th percentile of normal), and many of these values were very high indeed. However, before the 13th week of pregnancy only one of the twenty-one cases (5%) had an A.F.P. value more than three times the median for unaffected pregnancies, and this value was not very high. This indicates that in antenatal screening for anencephaly or spina bifida, A.F.P. should be measured in blood taken from the mother during the second trimester.

Anencephaly↗

Antenatal diagnosis of neural tube defects using a coated bead immunoassay for acetylcholinesterase in amniotic fluid.

The development and validation of a coated bead immunoassay for amniotic fluid acetylcholinesterase is outlined. The assay has good precision (between assay CV of 6.8% within the normal range), and is linear up to 250 arbitrary units/L. The clinical validity of this assay has been assessed using a panel of amniotic fluid samples from normal and abnormal pregnancies. At an assay cut off level of 200 arbitrary units/L, all cases of neural tube defect-affected pregnancies were identified and the number of false positives was very small. False positives resulted from severe blood staining of the amniotic fluid. Since the monoclonal antibody used recognises red cell membrane acetylcholinesterase and the stored amniotic fluids had been frozen and thawed a number of times, the extent of this problem needs to be further assessed using freshly collected samples. The performance of this assay was found to be superior to the differential inhibitor colorimetric method and close to that of the electrophoretic procedure. The quantitative nature of the assay and the independence from operator technique makes it a useful adjunct to the measurement of amniotic fluid AFP in the prenatal diagnosis of neural tube defects.

Acetylcholinesterase↗

Folate and cancer prevention: a new medical application of folate beyond hyperhomocysteinemia and neural tube defects.

Folate is an important cofactor in the transfer of one-carbon moieties and plays a key role in DNA synthesis, repair, and methylation. The role of folate has greatly evolved from the prevention of macrocytic anemia to the prevention of cardiovascular disease and neural tube defects. More recently, epidemiologic, animal, and clinical evidence suggests that folate may also play a role in cancer prevention. Two recently published large, prospective epidemiologic studies suggest that maintaining adequate levels of serum folate or moderately increasing folate intakes from dietary sources and vitamin supplements can significantly reduce the risk of pancreatic and breast cancer, respectively. This protective effect of folate appears to be operative in subjects at risk for developing these cancers, namely, male smokers for pancreatic cancer and women regularly consuming a moderate amount of alcohol for breast cancer. Because the expanding role of folate nutrition in cancer prevention has major public health implications, research is required to clearly elucidate the effect of folate on carcinogenesis.

Adolescent↗

Comparative physical and transcript maps of approximately 1 Mb around loop-tail, a gene for severe neural tube defects on distal mouse chromosome 1 and human chromosome 1q22-q23.

The homozygous loop-tail (Lp) mouse has a severe neural tube closure defect, analogous to the craniorachischisis phenotype seen in humans. Linkage analysis and physical mapping have previously localized the Lp locus to a region on mouse chromosome 1 defined by the markers D1Mit113-Tagln2. Here we report the construction of sequence-ready bacterial clone contigs encompassing the Lp critical region in both mouse and the orthologous human region (1q22-q23). Twenty-two genes, one EST, and one pseudogene have been identified using a combination of EST database screening, exon amplification, and genomic sequence analysis. The preliminary gene map is Cen-Estm33-AA693056-Ly9-Cd48-Slam-Cd84-Kiaa1215-Nhlh1-Kiaa0253-Copa-Pxf-H326-Pea15-Casq1-Atp1a4-Atp1a2-Estm34-Kcnj9-Kcnj10-Kiaa1355-Tagln2-Nesg1-Crp-Tel. The genes between Slam and Kiaa1355 are positional candidates for Lp. The comparative gene content and order are identical between mouse and human, indicating a high degree of conservation between the two species in this region. Together, the physical and transcript maps described here serve as resources for the identification of the Lp mutation and further define the conservation of this genomic region between mouse and human.

Adult↗

Fumonisins disrupt sphingolipid metabolism, folate transport, and neural tube development in embryo culture and in vivo: a potential risk factor for human neural tube defects among populations consuming fumonisin-contaminated maize.

Fumonisins are a family of toxic and carcinogenic mycotoxins produced by Fusarium verticillioides (formerly Fusarium moniliforme), a common fungal contaminant of maize. Fumonisins inhibit ceramide synthase, causing accumulation of bioactive intermediates of sphingolipid metabolism (sphinganine and other sphingoid bases and derivatives) as well as depletion of complex sphingolipids, which interferes with the function of some membrane proteins, including the folate-binding protein (human folate receptor alpha). Fumonisin causes neural tube and craniofacial defects in mouse embryos in culture. Many of these effects are prevented by supplemental folic acid. Recent studies in LMBc mice found that fumonisin exposure in utero increases the frequency of developmental defects and administration of folate or a complex sphingolipid is preventive. High incidences of neural tube defects (NTD) occur in some regions of the world where substantial consumption of fumonisins has been documented or plausibly suggested (Guatemala, South Africa, and China); furthermore, a recent study of NTD in border counties of Texas found a significant association between NTD and consumption of tortillas during the first trimester. Hence, we propose that fumonisins are potential risk factors for NTD, craniofacial anomalies, and other birth defects arising from neural crest cells because of their apparent interference with folate utilization.

Animals↗

Public drinking water contamination and birth outcomes.

The effects of public drinking water contamination on birth outcomes were evaluated in an area of northern New Jersey. After excluding plural births and chromosomal defects, 80,938 live births and 594 fetal deaths that occurred during the period 1985-1988 were studied. Information on birth outcome status and maternal risk factors was obtained from vital records and the New Jersey Birth Defects Registry. Monthly exposures during pregnancy were estimated for all births using tap water sample data. Odds ratios of > or = 1.50 were found for the following: total trihalomethanes with small for gestational age, central nervous system defects, oral cleft defects, and major cardiac defects; carbon tetrachloride with term low birth weight, small for gestational age, very low birth weight, total surveillance birth defects, central nervous system defects, neural tube defects, and oral cleft defects; trichloroethylene with central nervous system defects, neural tube defects, and oral cleft defects; tetrachloroethylene with oral cleft defects; total dichloroethylenes with central nervous system defects and oral cleft defects; benzene with neural tube defects and major cardiac defects; and 1,2-dichloroethane with major cardiac defects. Total trihalomethane levels > 100 ppb reduced birth weight among term births by 70.4 g. By itself, this study cannot resolve whether the drinking water contaminants caused the adverse birth outcomes; therefore, these findings should be followed up utilizing available drinking water contamination databases.

Bias↗

Triploid partial molar pregnancy and fetal neural tube defect detected through Down's syndrome screening.

A third case of triploid partial molar pregnancy with fetal neural tube and abdominal-wall defect, detected through maternal serum alphafetoprotein and hCG screening for Down's syndrome is reported. A 23-year-old woman had elevated serum alphafetoprotein and hCG levels at routine screening at the 16th week of gestation. Ultrasound examination suggested a fetal neural tube and abdominal-wall defect with thickened placenta. Amniocentesis was performed. A triploid karyotype (69 XXY) was confirmed with standard cytogenetic analysis. Fetal neural tube and abdominal wall defect was confirmed at the autopsy of the fetus. Placental histology was consistent with a hydatiform mole. When serum alphafetoprotein and hCG are elevated, during screening for Down's syndrome, the possibility of a partial molar pregnancy with fetal malformation should be added to the differential diagnosis.

Abdominal Muscles↗