NEIGHBORHOOD-LEVEL SOCIOECONOMIC POSITION DURING EARLY PREGNANCY AND THE RISK OF GASTROSCHISIS

Background: Studies have shown that pregnant women in low socioeconomic neighborhoods are at a higher risk of adverse pregnancy outcomes, including birth defects. However, few studies have explored this association with gastroschisis. Using data from the National Birth Defects Prevention Study (NBDPS), we investigated the association between neighborhood-level socioeconomic position (nSEP) during early pregnancy and the risk of gastroschisis, and evaluated whether nSEP modifies the associations between maternal age at conception and pre-pregnancy body mass index (BMI) and gastroschisis. Methods: We analyzed data from singleton case infants diagnosed with gastroschisis and singleton non-malformed control infants delivered between 1997 and 2011. To characterize nSEP, two principal component analysis (PCA)-derived indices were constructed including the Neighborhood Deprivation Index (NDI) and a Neighborhood-level Socioeconomic Position Index (nSEPI). Maternal neighborhood was defined as the self-reported address mothers lived at the longest between one month prior to conception to the third month of pregnancy. Generalized estimating equations were used to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs), and relative excess risks due to interaction (RERI) were calculated to assess modification by nSEP on the additive scale. Results: Mothers in moderate (NDI aOR: 1.25; 95% CI: 1.05, 1.49 and nSEPI aOR: 1.25; 95% CI: 1.04, 1.49) or low SEP neighborhoods (NDI aOR; 1.27; 95% CI: 1.05 1.54 and nSEPI aOR: 1.32, 95% CI: 1.09, 1.61) were more likely to deliver an infant with gastroschisis compared with mothers in high SEP neighborhoods. Residing in low SEP neighborhoods sub-additively modified the association between maternal age at conception and gastroschisis. Young mothers (< 20 years) in high SEP neighborhoods had double the risk of having an infant with gastroschisis (aOR: 6.55; 95% CI: 4.59, 9.35) compared with young mothers in low SEP neighborhoods (aOR: 3.13, 95% CI: 2.59, 3.78). However, nSEP did not modify the association between pre-pregnancy BMI and gastroschisis. Regardless of nSEP, young maternal age at conception and normal or underweight BMI were consistently associated with elevated odds of gastroschisis. Conclusions: Future studies of nSEP should consider examining potential mechanisms through which contextual factors may influence individual-level characteristics and/or its association with gastroschisis.Doctor of Philosoph

Homologous Recombination and Translesion DNA Synthesis Play Critical Roles on Tolerating DNA Damage Caused by Trace Levels of Hexavalent Chromium

Contamination of potentially carcinogenic hexavalent chromium (Cr(VI)) in the drinking water is a major public health concern worldwide. However, little information is available regarding the biological effects of a nanomoler amount of Cr(VI). Here, we investigated the genotoxic effects of Cr(VI) at nanomoler levels and their repair pathways. We found that DNA damage response analyzed based on differential toxicity of isogenic cells deficient in various DNA repair proteins is observed after a three-day incubation with K2CrO4 in REV1-deficient DT40 cells at 19.2 μg/L or higher as well as in TK6 cells deficient in polymerase delta subunit 3 (POLD3) at 9.8 μg/L or higher. The genotoxicity of Cr(VI) decreased ~3000 times when the incubation time was reduced from three days to ten minutes. TK mutation rate also significantly decreased from 6 day to 1 day exposure to Cr(VI). The DNA damage response analysis suggest that DNA repair pathways, including the homologous recombination and REV1- and POLD3-mediated error-prone translesion synthesis pathways, are critical for the cells to tolerate to DNA damage caused by trace amount of Cr(VI)

Homologous Recombination and Translesion DNA Synthesis Play Critical Roles on Tolerating DNA Damage Caused by Trace Levels of Hexavalent Chromium

Contamination of potentially carcinogenic hexavalent chromium (Cr(VI)) in the drinking water is a major public health concern worldwide. However, little information is available regarding the biological effects of a nanomoler amount of Cr(VI). Here, we investigated the genotoxic effects of Cr(VI) at nanomoler levels and their repair pathways. We found that DNA damage response analyzed based on differential toxicity of isogenic cells deficient in various DNA repair proteins is observed after a three-day incubation with K2CrO4 in REV1-deficient DT40 cells at 19.2 μg/L or higher as well as in TK6 cells deficient in polymerase delta subunit 3 (POLD3) at 9.8 μg/L or higher. The genotoxicity of Cr(VI) decreased ~3000 times when the incubation time was reduced from three days to ten minutes. TK mutation rate also significantly decreased from 6 day to 1 day exposure to Cr(VI). The DNA damage response analysis suggest that DNA repair pathways, including the homologous recombination and REV1- and POLD3-mediated error-prone translesion synthesis pathways, are critical for the cells to tolerate to DNA damage caused by trace amount of Cr(VI)

Long noncoding RNA expression in the cervix mid-pregnancy is associated with the length of gestation at delivery

<p>Infants born preterm are at increased risk of multiple morbidities and mortality. Why some women deliver preterm remains poorly understood. Prior studies have shown that cervical microRNA expression and DNA methylation are associated with the length of gestation. However, no study has examined the role of long noncoding RNAs (lncRNAs) in the cervix during pregnancy. To determine whether expression of lncRNAs is associated with length of gestation at delivery, we analyzed RNA from cervical swabs obtained from 78 women during pregnancy (mean 15.5, SD 5.0, weeks of gestation) who were participating in the Spontaneous Prematurity and Epigenetics of the Cervix (SPEC) Study in Boston, MA, USA. We used a PCR-based platform and found that 9 lncRNAs were expressed in at least 50% of the participants. Of these, a doubling of the expression of <i>TUG1, TINCR</i>, and <i>FALEC</i> was associated with shorter lengths of gestation at delivery [2.8 (95% CI: 0.31, 5.2); 3.3 (0.22, 6.3); and 4.5 (7.3, 1.6) days shorter respectively]. Of the lncRNAs analyzed, none was statistically associated with preterm birth, but expression of <i>FALEC</i> was 2.6-fold higher in women who delivered preterm vs. term (<i>P </i>= 0.051). These findings demonstrate that lncRNAs can be measured in cervical samples obtained during pregnancy and are associated with subsequent length of gestation at delivery. Further, this study supports future work to replicate these findings in other cohorts and perform mechanistic studies to determine the role of lncRNAs in the cervix during pregnancy.</p

K₂CrO₄ reduces the viability of human cells deficient in certain DNA repair pathways at Cr(VI) levels detected in U.S. city water.

<p>HeLa cells (A) and TK6 cells (B) transiently or stably knocked down with shRNA against <i>RAD54</i>, <i>BRCA1</i>, or <i>POLD3</i> were exposed to K₂CrO₄ for ~3 days to determine their survival rate. (C) Point of departure analysis of TK6 indicated significant differences (p<0.0001) for TK6 control (log10(BMD) = 1.53, exponential model) vs. <i>POLD3</i> shRNA knock down (log10(BMD) = 0.99 (9.8 μg/L), polynomial model). The black arrow indicates the maximum contaminant levels (MCL) set by the U.S. EPA. The open arrow shows the highest Cr(VI) levels detected in US city water.</p

K₂CrO₄ reduces viability of human cells as well as DT40 cells deficient in certain DNA repair pathways at the maximum contaminant levels (MCL) set by the U.S. EPA.

<p>Various human cells (A) and DT40 parental cells and their mutant cells (B) deficient in <i>REV1</i>, <i>BRCA1</i>, or <i>RAD54</i> were exposed to K₂CrO₄ for ~3 days to determine their survival rates. Survival data were log-transformed giving approximate normality using Prism 5. Each LC₅₀ value was then calculated. The black arrow indicates the maximum contaminant levels (MCL) set by the U.S. EPA, while the open arrow shows the highest Cr(VI) levels detected in U.S. city water (12.9 μg/L). (C) Point-of-departure analysis showed a significant difference (p<0.0001) in DT40 (log10(BMD) = 1.98 by the Hill model) vs. <i>REV1</i>-deficient cells (log10(BMD) = 1.28 (19.2 μg/L) by the Hill model). (D) DT40 cell-based DNA damage response analysis was performed for K₂CrO₄ using a series of DT40 mutants. Relative LC₅₀ values were normalized according to the LC₅₀ value of the parental (wild type) DT40 cells. Error bars represent standard deviation from at least three independent experiments. Student’s t-test was used to test for significance in mean LC₅₀ values between DT40 parental cells and each mutant. Columns shaded in gray indicate significant differences (p<0.05) between parental DT40 cells and each mutant. Columns shaded in black show the cell lines (<i>REV1</i>, <i>RAD54</i>, <i>POLD3</i>, and <i>BRCA1</i> mutants) that are markedly sensitive to K₂CrO₄. (p<0.05 for all four cell lines after Bonferroni adjustment for 32 tests).</p

The genotoxicity of K₂CrO₄ in human and DT40 cells is drastically decreased when K₂CrO₄ incubation time is reduced.

<p>(A) <i>REV1</i> ko DT40 cells were incubated with K₂CrO₄ for 10 min to 8 hours followed by extensive washing. The cells were further cultivated for 3 days in fresh medium without addition of K₂CrO₄ to determine cell survival. (B) The exposure times (hours) were multiplicatively inversed followed by log transformation (x-axis). LC₅₀ data for each exposure time were log transformed (y-axis). Linear regression analysis was performed to determine the relationship between exposure time and LC₅₀ values (p<0.0001). (C) TK6 <i>POLD3</i> knock-down cells and TK6 mock shRNA-treated cells were incubated with K₂CrO₄ for 10 min followed by extensive washing. The cells were further cultivated for 3 days in fresh medium without addition of K₂CrO₄ to determine cell survival. The survival curves were compared between 10-min and 3-day exposure groups (p<0.0001). The green arrow indicates the Cr(VI) concentration (172,000 μg/L) that causes an increase in oral cancer, a finding that was previously shown in an NTP rodent study [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0167503#pone.0167503.ref007" target="_blank">7</a>].</p