Genetic variation in biotransformation enzymes,air pollution exposures,and risk of spina bifida

Spina bifida is a birth defect characterized by incomplete closure of the embryonic neural tube. Genetic factors as well as environmental factors have been observed to influence risks for spina bifida. Few studies have investigated possible gene‐environment interactions that could contribute to spina bifida risk. The aim of this study is to examine the interaction between gene variants in biotransformation enzyme pathways and ambient air pollution exposures and risk of spina bifida. We evaluated the role of air pollution exposure during pregnancy and gene variants of biotransformation enzymes from bloodspots and buccal cells in a California population‐based case‐control (86 cases of spina bifida and 208 non‐malformed controls) study. We considered race/ethnicity and folic acid vitamin use as potential effect modifiers and adjusted for those factors and smoking. We observed gene‐environment interactions between each of the five pollutants and several gene variants: NO (ABCC2), NO₂ (ABCC2, SLC01B1), PM₁₀ (ABCC2, CYP1A1, CYP2B6, CYP2C19, CYP2D6, NAT2, SLC01B1, SLC01B3), PM_2.5 (CYP1A1 and CYP1A2). These analyses show positive interactions between air pollution exposure during early pregnancy and gene variants associated with metabolizing enzymes. These exploratory results suggest that some individuals based on their genetic background may be more susceptible to the adverse effects of pollution.     

Degree of genetic homozygosity and distribution of AB0 blood types among patients with spina bifida occulta and spina bifida aperta

Introduction

Assuming that spina bifida (SB) is a genetically controlled disease, the aim of our study was to evaluate the degree of genetic homozygosity and the distribution of AB0 blood types among patients with SB occulta and SB aperta by the homozygously recessive characteristics (HRC) test.

Material and methods

Our study included an analysis of the presence, distribution and individual combination of 15 selected genetically controlled morpho-physiological traits in a sample of 100 patients with SB (SB occulta N = 50 and SB aperta N = 50) and a control group of individuals (N = 100).

Results

We found a statistically significant difference between the mean values for genetic homozygosity (SB 4.5 ±0.3; control 3.0 ±0.2, p < 0.001) and also differences in the presence of certain individual combinations of such traits. In 12 (80.0%) of the 15 observed characteristics, recessive homozygosity was expressed to a greater degree among the group of SB patients, while for 9 (60.0%) of the traits this level of difference was statistically significant (Σ_χ ² = 266.3, p < 0.001). There was no difference in average homozygosity of such genetic markers between groups of SB occulta and SB aperta patients, but the type of individual variation in the two studied groups significantly differed. In the group of patients with SB the frequency of 0 blood group was significantly increased while B blood group was significantly decreased.

Conclusions

Our results clearly show that there is a populational genetic difference in the degree of genetic homozygosity and variability between the group of patients with SB and individuals without clinical manifestations, indicating a possible genetic component in the aetiopathogenesis of spina bifida.     

Distribution of affected muscles and degree of neurogenic lesion in patients with spina bifida

Introduction

Patients with spina bifida in the lumbosacral region usually have various degrees of motor and sensory dysfunctions of the lower extremities and anal sphincter. The aim of our study was to evaluate the distribution and differences in frequencies of affected muscles, number of affected muscles and degree of neurogenic lesion between patients with spina bifida occulta (SBO) and spina bifida aperta (SBA).

Material and methods

In 100 patients with SB, 6 muscles in the lower limbs were separately analysed. Due to the number of affected muscles, we evaluated 5 groups of patients: with 1 affected muscle, 2 affected muscles, 3 affected muscles, 4 affected muscles and 5 affected muscles. Three degrees of neurogenic lesions were assessed: mild, moderate and severe.

Results

The tibialis anterior muscle was most frequently affected in SB patients. The outer anal sphincter was frequently affected in the group of SBA patients. Single muscle affection is frequent in the group of patients with SBO, while in the group of patients with SBA, 4 muscles were significantly frequently affected. The great majority of patients (45.46%) with affected outer anal sphincter (OAS) in the group of SBO were without affection of other muscles, while for the SBA group it was for every third patient. Mild neurogenic lesion was significantly frequent in SBO patients, while severe form was significantly frequent in SBA patients.

Conclusions

Patients with SBO usually present with mild to moderate clinical presentation, while multiple root involvement and severe degree of neurogenic lesion is associated more frequently with SBA.     

Evaluation of 64 candidate single nucleotide polymorphisms as risk factors for neural tube defects in a large Irish study population

Individual studies of the genetics of neural tube defects (NTDs) contain results on a small number of genes in each report. To identify genetic risk factors for NTDs, we evaluated potentially functional single nucleotide polymorphisms (SNPs) that are biologically plausible risk factors for NTDs but that have never been investigated for an association with NTDs, examined SNPs that previously showed no association with NTDs in published studies, and tried to confirm previously reported associations in folate‐related and non‐folate‐related genes. We investigated 64 SNPs in 34 genes for association with spina bifida in up to 558 case families (520 cases, 507 mothers, 457 fathers) and 994 controls in Ireland. Case‐control and mother‐control comparisons of genotype frequencies, tests of transmission disequilibrium, and log‐linear regression models were used to calculate effect estimates. Spina bifida was associated with over‐transmission of the LEPR (leptin receptor) rs1805134 minor C allele [genotype relative risk (GRR): 1.5; 95% confidence interval (CI): 1.0–2.1; P = 0.0264] and the COMT (catechol‐O‐methyltransferase) rs737865 major T allele (GRR: 1.4; 95% CI: 1.1–2.0; P = 0.0206). After correcting for multiple comparisons, these individual test P‐values exceeded 0.05. Consistent with previous reports, spina bifida was associated with MTHFR 677C>T, T (Brachyury) rs3127334, LEPR K109R, and PDGFRA promoter haplotype combinations. The associations between LEPR SNPs and spina bifida suggest a possible mechanism for the finding that obesity is a NTD risk factor. The association between a variant in COMT and spina bifida implicates methylation and epigenetics in NTDs. © 2010 Wiley‐Liss, Inc.     

Sib risks of anencephaly and spina bifida in British Columbia

The prevalence at birth of anencephaly or spina bifida cystica among sibs of individuals born in British Columbia with these defects was studied using routinely collected records of morbidity and mortality within the province. The population prevalence of these neural-tube defects in British Columbia is approximately 1.55 per thousand births, lower than in other areas where family studies have been carried out. A total of 1,028 affected individuals born in British Columbia during the period 1952–1970 was ascertained from health and vital documents collected on an ongoing basis by the Division of Vital Statistics of the British Columbia Ministry of Health. Information on the families of these cases was acquired using computer-linked groupings of British Columbia marriage, birth, and stillbirth records. The risk of affected individuals among the sibs was 2.4%, about 15 times the population prevalence at birth. The prevalence among subsequent sibs of the first affected individual in a family was 2.1%. There was no difference in risk when various factors that influence the population incidence of these conditions were considered. The risk of recurrence of either of these anomalies after two previously affected sibs was 4.8%, or double the risk after one affected sib. From these results and those of a recent New York survey of sib risks of neural-tube anomalies it would seem that the risk of anencephaly and spina bifida cystica to sibs of affected cases in North America is approximately half the risk in Great Britain, and it is this lower risk of 2% that should be used for genetic counseling in North America.     

Relationships among life stress, perceived family environment, and the psychological distress of spina bifida adolescents

Fifty-three teen-agers with spina bifida participated in a mail survey and completed measures of recent life events, perceived family environment, and psychological distress. Low levels of perceived family conflict and control served as life stress buffers in the prediction of distress, whereas a high level of perceived independence served as a life stress exacerbator. These interaction effects differ from those obtained for a normal sample of adolescents in the lone previous study (Burt, Cohen, & Bjorck, 1988) that reported comparable analyses. The results suggest that the process by which family environments moderate stress adjustment differs for able-bodied vs. spina bifida adolescents.     

Predictors of parenting behavior trajectories among families of young adolescents with and without spina bifida

OBJECTIVE: To evaluate the utility of familial and parental variables in predicting trajectories of parenting behaviors among families of young adolescents with and without spina bifida (SB). METHOD: Sixty-eight families with a child with SB and a demographically matched comparison group (CG) of 68 families of an able-bodied child participated. Observational and questionnaire assessments of parenting behavior were collected via home visits at three time points, as were reports of parent and family functioning. RESULTS: Family conflict was negatively associated with adaptive parenting behavior at Time 1 (T1), but positively associated with adaptive parenting change. Although the direction of this effect was the same across both groups, findings were more robust for the SB sample. Among fathers of children with SB, parenting stress was positively associated with adaptive parenting at T1 but negatively associated with adaptive parenting change. In contrast, within the CG, paternal parenting stress was negatively associated with adaptive parenting at T1 but showed no enduring negative effects in longitudinal analyses. CONCLUSIONS: Family conflict and parenting stress were significant predictors of parenting behaviors and longitudinal parenting change. Findings are interpreted within a developmental context such that variables associated with maladaptive (or adaptive) parenting in the short run, may facilitate adaptive (or maladaptive) parenting over time based on young adolescents' changing developmental needs.     

Possible X-linked anencephaly and spina bifida—report of a kindred

Causal heterogeneity of anencephaly and spina bifida has been demonstrated; in rare families the neural tube defect may be caused by a single gene. We report a family in which four cases of anencephaly or spina bifida may represent X-linked inheritance.     

A longitudinal study of pubertal timing,parent-child conflict,and cohesion in families of young adolescents with spina bifida

OBJECTIVE: To study longitudinal associations between perceived pubertal timing and family conflict and cohesion during the transition to adolescence in 68 families of children with spina bifida and 68 matched families with able-bodied children. Children were 8 or 9 years old at Time 1 and 10 or 11 years old at Time 2. METHODS: Family conflict and cohesion were assessed with observational data and maternal, paternal, and child reports on questionnaires. Perceived pubertal timing was assessed with maternal report. RESULTS: Consistent with the literature on typically developing young adolescents, prospective longitudinal analyses revealed that early maturity was associated with higher levels of conflict and decreases in cohesion in families with able-bodied children. Contrary to these findings, perceived pubertal timing had less of an impact (or the opposite impact) in families of children with spina bifida. Findings were robust across respondents and methods of data collection. CONCLUSIONS: Findings based on multimethod and multisource data suggest that familial response to developmental change differs across context (spina bifida vs. able-bodied). Possible reasons for differential responses to the adolescent transition are reviewed. Services are likely to be enhanced if health professionals routinely discuss adolescent developmental issues with parents and youths during clinic visits.     

Influencing clinical practice regarding the use of antiepileptic medications during pregnancy: Modeling the potential impact on the prevalences of spina bifida and cleft palate in the United States

Selected antiepileptic drugs (AEDs) increase the risk of birth defects. To assess the impact of influencing AED prescribing practices on spina bifida and cleft palate we searched the literature for estimates of the association between valproic acid or carbamazepine use during pregnancy and these defects and summarized the associations using meta-analyses. We estimated distributions of the prevalence of valproic acid and carbamazepine use among women of childbearing age based on analyses of four data sets. We estimated the attributable fractions and the number of children born with each defect that could be prevented annually in the United States if valproic acid and carbamazepine were not used during pregnancy. The summary odds ratio estimate for the association between valproic acid and spina bifida was 11.9 (95% uncertainty interval (UI): 4.0–21.2); for valproic acid and cleft palate 5.8 (95% UI: 3.3–9.5); for carbamazepine and spina bifida 3.6 (95% UI: 1.3–7.8); and for carbamazepine and cleft palate 2.4 (95% UI: 1.1–4.5) in the United States. Approximately 40 infants (95% UI: 10–100) with spina bifida and 35 infants (95% UI: 10–70) with cleft palate could be born without these defects each year if valproic acid were not used during pregnancy; 5 infants (95% UI: 0–15) with spina bifida and 5 infants (95% UI: 0–15) with cleft palate could be born without these defects each year if carbamazepine were not used during pregnancy. This modeling approach could be extended to other medications to estimate the impact of translating pharmacoepidemiologic data to evidence-based prenatal care practice. Published 2011 Wiley-Liss, Inc.     

Loss of RAD9B impairs early neural development and contributes to the risk for human spina bifida

DNA damage response (DDR) genes orchestrating the network of DNA repair, cell cycle control, are essential for the rapid proliferation of neural progenitor cells. To date, the potential association between specific DDR genes and the risk of human neural tube defects (NTDs) has not been investigated. Using whole‐genome sequencing and targeted sequencing, we identified significant enrichment of rare deleterious RAD9B variants in spina bifida cases compared to controls (8/409 vs. 0/298; p = .0241). Among the eight identified variants, the two frameshift mutants and p.Gln146Glu affected RAD9B nuclear localization. The two frameshift mutants also decreased the protein level of RAD9B. p.Ser354Gly, as well as the two frameshifts, affected the cell proliferation rate. Finally, p.Ser354Gly, p.Ser10Gly, p.Ile112Met, p.Gln146Glu, and the two frameshift variants showed a decreased ability for activating JNK phosphorylation. RAD9B knockdowns in human embryonic stem cells profoundly affected early differentiation through impairing PAX6 and OCT4 expression. RAD9B deficiency impeded in vitro formation of neural organoids, a 3D cell culture model for human neural development. Furthermore, the RNA‐seq data revealed that loss of RAD9B dysregulates cell adhesion genes during organoid formation. These results represent the first demonstration of a DDR gene as an NTD risk factor in humans.     

Longitudinal study of observed and perceived family influences on problem-focused coping behaviors of preadolescents with spina bifida

OBJECTIVE: To study coping socialization longitudinally by examining reported and observed family environment and parenting variables in relation to children's problem-focused coping in a sample of 68 families of preadolescents with spina bifida and 68 matched able-bodied comparison families. METHODS: Family environment and parenting variables were assessed with mother and father reports and observational measures. Children's problem-focused coping was self-reported. RESULTS: Prospective analyses revealed that maternal responsiveness, paternal responsiveness, and family cohesion predicted an increase in children's use of problem-focused coping strategies, while change in paternal responsiveness and maternal responsiveness and demandingness was related concurrently to change in coping. Few group (spina bifida vs. able-bodied) or gender differences with respect to parenting and family influences on children's coping behaviors were found. CONCLUSIONS: Multimethod findings suggest that the quality of parenting and family environment is associated with children's problem-focused coping behaviors. We discuss clinical implications.     

Observed and perceived dyadic and systemic functioning in families of preadolescents with spina bifida

OBJECTIVE: To examine dyadic and systemic family functioning across several domains (conflict, cohesion, and stress) in families of preadolescents with spina bifida in comparison to families of able-bodied preadolescents (8- and 9-year olds; n = 68 in each sample). METHODS: Mother-, father-, and child-reported questionnaire data and observational ratings of family behavior were employed. RESULTS: Findings revealed significant group and socioeconomic status (SES) differences, particularly for the observational family data. Compared to families of able-bodied children, families in the spina bifida sample were less cohesive and children from this sample were more passive during family interaction tasks. Additional analyses suggested that some of these significant associations between group status and family functioning were mediated by verbal IQ, indicating that a significant portion (42%-55%) of the overall group effect was due to variations in child cognitive functioning. Lower SES families demonstrated higher levels of observed mother-child conflict, less observed and perceived family cohesion, and more life events. Lower SES families from the spina bifida sample appear to be particularly at risk for lower levels of family cohesion. CONCLUSIONS: Findings for the spina bifida sample support a resilience-disruption view (Costigan, Floyd, Harter, & McClintock, 1997) of systemic functioning in families of children with pediatric conditions.     

CNS malformations in the kraków region. I. Birth prevalence and seasonal incidence during 1979–1981

The birth prevalence of CNS malformations in the region of Krakow from 1979 to 1981 was determined to be 1.26/1000 from records of all live- and still-birth deliveries. The frequency of anencephaly was 0.23/1,000; spina bifida and encephalocele, 0.70/1000; isolated hydrocephaly, 0.26/1,000; and other CNS anomalies, 0.06/1,000. The observed rates are below the median European level. Female preponderance was found among the probands with anencephaly, encephalomeningocele, and myelomeningocele. Cytogenetic examination of 35 newborns with CNS malformations documented normal karyotypes in all neonates. The analysis of seasonal distribution of proband's birthdate and of date of mother's last menstrual period showed no significant seasonal trend.     

Lack of association between mutations in the folate receptor-α gene and spina bifida

Defects of neural tube closure are among the most common of all human malformations. Epidemiological and genetic studies indicate that most of these defects are multifactorial in origin with genetic and environmental causes. Although periconceptional supplementation of the maternal diet with folic acid has been shown to reduce the recurrence and occurrence of neural tube defects (NTDs) by up to 70%, the underlying mechanism remains unknown. Folic acid enters cells of certain tissues via a receptor-mediated process known as potocytosis. The folate receptor alpha (FR-α) gene codes for the protein responsible for binding folate, which is the first, and only, folate-dependent step in folate transport. The FR-α exons, which code for mature protein and the intron-exon boundaries, were examined for mutations in three separate studies. Initial screening was performed by single-stranded conformational polymorphism (SSCP) analysis in a subset of 1,688 samples obtained from a population-based case-control study of NTDs in California. In the second study, the DNA sequence of exons 5 and 6 was determined in a group of 50 NTD affected individuals. The final experiment involved using dideoxy fingerprinting (ddF) to screen a population-based case-control sample of 219 individuals who were stratified into four sub-groups on the basis of folate intake and pregnancy outcome. No polymorphism was detected in any of the four exons examined. It is unlikely that the beneficial effects of maternal folate supplementation in preventing NTDs acts through a mechanism involving pharmacological correction of a variant form of folate receptor alpha. Am. J. Med. Genet. 76:310–317, 1998. © 1998 Wiley-Liss, Inc.     

Molecular genetic analysis of the gene encoding the trifunctional enzyme MTHFD (methylenetetrahydrofolate-dehydrogenase, methenyltetrahydrofolate-cyclohydrolase, formyltetrahydrofolate synthetase) in patients with neural tube defects

It is now well recognized that periconceptional folic acid or folic acid containing multivitamin supplementation reduces the risk of neural tube defects (NTDs). Recently we were able to show that homozygosity for a thermolabile variant of the enzyme methylenetetrahydrofolate reductase is associated with an increased risk for spina bifida in patients recruited from the Dutch population. However, this genetic risk factor could not account for all folic acid preventable NTDs. In an attempt to identify additional folate related enzymes that contribute to NTD etiology we now studied the methylenetetrahydrofolate dehydrogenase gene on chromosome 14q24 which encodes a single protein with three catalytic properties important in the folate metabolism. The cDNA sequence of 38 familial and 79 sporadic patients was screened for the presence of mutations by single strand conformation polymorphism (SSCP) analysis followed by sequencing. Two amino acid substitutions were identified. The first one (R293H) was detected in a patient with familial spina bifida and not in 300 control individuals. The mutation was inherited from the unaffected maternal grandmother and was also present in two younger brothers of the index patient, one of them displaying spina bifida occulta and the other being unaffected. The second change turned out to be an amino acid polymorphism (R653Q) that was present in both patients and controls with similar frequencies. Our results so far provide no evidence for a major role of the methylenetetrahydrofolate-dehydrogenase (MTHFD) gene in NTD etiology. However, the identification of a mutation in one family suggests that this gene can act as a risk factor for human NTD.     

Isolated and ventriculomegaly-associated cases of spina bifida in genetic counseling: Focus on fetal pathology

Cases of spina bifida alone and in association with ventriculomegaly represent important but different malformations according to clinical characteristics.     

Determination of independent risk factors and comparative analysis of diagnostic methods for immediate type latex allergy in spina bifida patients

Background Development of allergy to natural rubber latex in spina bifida patients is determined by several risk factors, such as age, number of interventions and atopic disease that are, however, interdependent. Furthermore, several diagnostic procedures have been analysed, but a comprehensive analysis of their diagnostic significance is lacking. Objective To determine the independent major risk factor(s) for development of natural rubber latex allergy and the most valuable diagnostic procedure. Methods In aselectively collected spina bifida patients, we correlated existing natural rubber latex allergy with age, sex, atopy and the number of hospitalizations and of surgical interventions in appropriately matched subgroups. Allergy to natural rubber latex was established by application of a latex glove fragment on the skin. Skin-prick tests with glove eluate, a natural latex extract and a commercial latex extract were carried out as were specific IgE measurements by radioimmuno assay (RAST-CAP). The results of the latex application test are compared with the other diagnostic methods. Results Out of 74 fully evaluated patients, 17 had a positive application test. The number of surgical interventions correlates strongly with the presence of natural rubber latex allergy (P < 0.0002), independent of age, sex and presence of atopy. Skin-prick tests with unstandardized allergens made from known high allergenic latex gloves represent the most sensitive diagnostic method, with the highest negative predictive value and a specificity of 0.95. RAST-CAP was the next best method with a specificity of 0.93, a sensitivity of 0.89 and a negative predictive value of 0.97. Conclusion The number of surgical interventions is the major independent determining factor for allergy to natural rubber latex in spina bifida patients. Unstandardized skin-prick tests are the most sensitive and specific diagnostic tool, but RAST-CAP is almost equally performant and therefore a valid alternative.     

Secular trends in congenital anomaly‐related fetal and infant mortality in Canada, 1985–1996

Prenatal diagnosis of major congenital anomalies and subsequent termination of affected pregnancies has been widely available as part of routine obstetric care in recent years. In this study, vital statistical data on stillbirths, live births, and infant deaths were used to examine secular trends in gestational age‐specific and category‐specific fetal and infant mortality due to congenital anomalies in Canada (excluding Ontario and Newfoundland) from 1985–1996. Comparisons of the rates between 1985–1987 and 1994–1996 were made using relative risks and 95% confidence intervals (CI). The overall fetal mortality rate due to congenital anomalies increased significantly, from 68.0 per 100,000 total births in 1985–1987 to 78.6 per 100,000 total births in 1994–1996, while the overall infant mortality rate due to congenital anomalies decreased significantly over the same period, from 2.47 to 1.79 per 1,000 live births. The fetal death rate due to congenital anomalies at 20–21 weeks of gestation increased approximately five‐fold (relative risk [RR] = 4.83, 95% CI = 3.28–7.11) from 4.5 to 21.5 per 100,000 fetuses at risk, while the rate at 37–41 weeks decreased by 30% (RR = 0.70, 95% CI = 0.50–0.97). Fetal death rates among pregnancies at 20–25 weeks of gestation increased in all categories of congenital anomaly except anencephaly and respiratory system anomalies. Congenital anomaly‐related fetal and infant deaths have increased at early gestation but declined at later gestation in Canada. These changes suggest an increase in prenatal diagnosis and selective termination of pregnancies with congenital anomalies in recent years. © 2001 Wiley‐Liss, Inc.