Yuanyuan Li

Tissue-specific distribution of aberrant DNA methylation associated with maternal low-folate status in human neural tube defects

This study compares the density and tissue-specific distribution of 5-methyl cytosine (5mC) in genomic DNA from human fetuses with or without neural tube defects (NTD) and examines whether low maternal serum folate is a possible correlate and/or risk factor for NTD. The results demonstrate significant hypomethylation of brain genomic DNA in NTD fetuses relative to controls (P<.01), as well as relative hypermethylation of skin and heart in NTD fetuses. In normal fetuses, the level of 5mC in liver genomic DNA decreased from fetal week 18 to 28 and increased over the same developmental period in kidney genomic DNA, but these trends were absent in genomic DNA from NTD fetuses. Mean maternal serum folate was significantly lower in NTD fetuses than in controls (P<.01), and maternal serum folate correlated with density of 5mC in genomic brain DNA from NTD fetuses (r=0.610). The results indicate that aberrant DNA methylation in NTD may be due to maternal folate deficiency and may be involved in the pathogenesis of NTD in humans.

MicroRNAs: potential regulators involved in human anencephaly.

MicroRNAs (miRNAs) are posttranscriptional regulators of messenger RNA activity. Neural tube defects (NTDs) are severe congenital anomalies that substantially impact an infants morbidity and mortality. The miRNAs are known to be dynamically regulated during neurodevelopment; their role in human NTDs, however, is still unknown. In this study, we show the presence of a specific miRNA expression profile from tissues of fetuses with anencephaly, one of the most severe forms of NTDs. Furthermore, we map the target genes of these miRNAs in the human genome. In comparison to healthy human fetal brain tissues, tissues from fetuses with anencephaly exhibited 97 down-regulated and 116 up-regulated miRNAs. The microarray findings were extended using real-time qRT-PCR for nine miRNAs. Specifically, of these validated miRNAs, miR-126, miR-198, and miR-451 were up-regulated, while miR-9, miR-212, miR-124, miR-138, and miR-103/107 were down-regulated in the tissues of fetuses with anencephaly. A bioinformatic analysis showed 881 potential target genes that are regulated by the validated miRNAs. Seventy-nine of these potential genes are involved in a protein interaction network. There were 6 co-occurrence annotations within the GOSlim process and 7 co-occurrence annotations within the GOSlim function found by GeneCodis 2.0. Our results suggest that miRNA dysregulation is possibly involved in the pathogenesis of anencephaly.

Association between MTR A2756G and MTRR A66G polymorphisms and maternal risk for neural tube defects: A meta-analysis

BACKGROUNDnMethionine synthase (MTR) and methionine synthase reductase (MTRR) genes have been considered to be implicated in the development of neural tube defects (NTDs). However, the results are inconsistent. Accordingly, we conducted a meta-analysis to further investigate such an association.nnnMETHODSnPublished literature from PubMed and Embase databases was retrieved. All studies evaluating the association between MTR A2756G or MTRR A66G polymorphism and maternal risk for NTDs were included. Pooled odds ratio (OR) with 95% confidence interval (CI) was calculated using the fixed- or random-effects model.nnnRESULTSnA total of 11 studies (1005 cases and 2098 controls) on MTR A2756G polymorphism and 10 studies (1211 cases and 2003 controls) on MTRR A66G polymorphism were included. Overall, this meta-analysis revealed no significant association between maternal MTR A2756G polymorphism and NTD susceptibility in either genetic model. A significant association between MTRR A66G polymorphism and maternal risk for NTDs was observed for GG vs. AA (OR=1.31, 95% CI 1.03-1.67) among Caucasians.nnnCONCLUSIONnThe present meta-analysis indicated that MTRR A66G polymorphism, but not MTR A2756G, is significantly associated with maternal risk for NTDs in Caucasians.

Association of genomic instability, and the methylation status of imprinted genes and mismatch-repair genes, with neural tube defects

We studied the genomic instability and methylation status of the mismatch-repair (MMR) genes hMLH1 and hMSH2, and the imprinted genes H19/IGF2, in fetuses with neural tube defects (NTDs) to explore the pathogenesis of the disease. Microsatellite instability (MSI) was observed in 23 of 50 NTD patients. Five NTD patients showed high-degree MSI (MSI-H) and 18 showed low-degree MSI (MSI-L). The frequencies of mutated microsatellite loci were 3/50 (6%) for BatT-25, 10/50 (20%) for Bat-26, 3/50 (6%) for Bat34C4, 6/50 (12%) for D2S123, 4/50 (8%) for D2S119, and 3/50 (6%) for D3S1611. The promoter regions of the hMLH1 and hMSH2 genes were unmethylated in NTD patients, as determined by methylation-specific PCR. The hMLH1 and hMSH2 promoter methylation patterns, the methylation levels of H19 DMR1, and IGF2 DMR0 were detected by bisulfite sequencing PCR, sub-cloning, and sequencing. The hMSH2 promoter sequence was unmethylated, and the hMLH1 promoter showed a specific methylation pattern at two CpG sites. The methylation levels of H19 DMR1 in the NTD and control groups are 73.3%±15.9 and 58.3%±11.2, respectively. The methylation level of the NTD group was higher than that of the control group (Students t-test, P<0.05). There is no significant difference in IGF2 DMR0 methylation level between the two groups. All of the results presented here suggest that genomic instability, the MMR system, and hyper-methylation of the H19 DMR1 may be correlated with the occurrence of NTDs.

Mechanism of folate deficiency-induced apoptosis in mouse embryonic stem cells: Cell cycle arrest/apoptosis in G1/G0 mediated by microRNA-302a and tumor suppressor gene Lats2.

Deficiencies in maternal diet, such as inadequate intake of folate, can inhibit normal development and lead to developmental defects. MicroRNAs (miRNAs) may play a role in mediating the effects of folate deficiency in the growing mammalian embryo, although conclusive evidences to support that possibility are not yet available. The goal of the present study was to investigate whether and how folate deprivation alters the properties of mouse embryonic stem cells (mESCs) in culture. For this purpose, mESCs were cultured in folate-deficient or complete culture medium. The results show that folate-deficient mESCs have a significantly higher rate of apoptosis, accumulate in G0/G1 and fail to proliferate. Expression profiling revealed several miRs and many mRNAs are differently expressed in folate-deficient cells. RT-PCR data confirmed differential expressions of 12 miRNAs in folate-deficient cells. Furthermore, bioinformatics analyses and in vitro studies suggested that miR-302a plays a critical role in mediating the effects of folate on cell proliferation and cell cycle-specific apoptosis by targeting Lats2 gene. Together, these results suggest that the effects of folate deficiency on mammalian development may be mediated by miRNAs that regulate proliferation and/or cell cycle progression in ESCs.

Cystathionine beta-synthase 844ins68 polymorphism is unrelated to susceptibility to neural tube defects.

OBJECTIVEnCystathionine beta-synthase (CBS) 844ins68 polymorphism has been implicated in the development of neural tube defects (NTDs). However, the results of different studies are inconsistent. Thus, we conducted a meta-analysis to further investigate this association.nnnMETHODSnPublished studies were retrieved from PubMed, Embase, China National Knowledge Infrastructure, and Wanfang Data. Studies that evaluated the association between CBS 844ins68 polymorphism and NTD risk among mothers, children, or fathers were included. The pooled odds ratios with 95% confidence interval were calculated using a fixed effects model or a random effects model.nnnRESULTSnA total of eight studies on mothers (641 cases and 1145 controls), eight studies on children (852 cases and 1912 controls), and five studies (263 cases and 1562 controls) on fathers were included. The meta-analysis revealed no significant association between CBS 844ins68 polymorphism and NTD risk among mothers, children, and fathers under either genetic model.nnnCONCLUSIONnThe present meta-analysis indicates that CBS 844ins68 polymorphism is not a good predictor of risk for NTDs.

Meta-analyses on the association of MTR A2756G and MTRR A66G polymorphisms with neural tube defect risks in Caucasian children

Abstract Objective: Methionine synthase (MTR) and MTR reductase (MTRR) genes have been considered to be implicated in the development of neural tube defects (NTDs). The associations between MTR A2756G and MTRR A66G polymorphisms and NTD risk in children have been investigated in many studies. However, results are inconsistent. Accordingly, we conducted meta-analyses to further investigate such associations. Methods: Published literatures were obtained from PubMed and Embase databases. All studies evaluating the association between MTR A2756G or MTRR A66G polymorphism and infant NTDs were included. Pooled odds ratio with a 95% confidence interval was calculated using fixed or random-effects model. Results: A total of 13 studies (1298 cases and 2237 controls) on MTR A2756G polymorphism and 10 studies (1358 cases and 2169 controls) on MTRR A66G polymorphism were included. Meta-analyses reveal no significant association of MTR A2756G and MTRR A66G polymorphisms with risk for NTDs in Caucasian children in either the genetic model or allele model. Conclusions: The present meta-analyses indicate that MTR A2756G and MTRR A66G polymorphism are not associated with NTD risks in Caucasian children.

Association between Long Interspersed Nuclear Element-1 Methylation and Relative Telomere Length in Wilms Tumor

Background:DNA hypomethylation of long interspersed nuclear elements-1 (LINEs-1) occurs during carcinogenesis, whereas information addressing LINE-1 methylation in Wilms tumor (WT) is limited. The main purpose of our study was to quantify LINE-1 methylation levels and evaluate their relationship with relative telomere length (TL) in WT. Methods:We investigated LINE-1 methylation and relative TL using bisulfite-polymerase chain reaction (PCR) pyrosequencing and quantitative PCR, respectively, in 20 WT tissues, 10 normal kidney tissues and a WT cell line. Significant changes were analyzed by t-tests. Results:LINE-1 methylation levels were significantly lower (P < 0.05) and relative TLs were significantly shorter (P < 0.05) in WT compared with normal kidney. There was a significant positive relationship between LINE-1 methylation and relative TL in WT (r = 0.671, P = 0.001). LINE-1 Methylation levels were significantly associated with global DNA methylation (r = 0.332, P < 0.01). In addition, relative TL was shortened and LINE-1 methylation was decreased in a WT cell line treated with the hypomethylating agent 5-aza-2′-deoxycytidine compared with untreated WT cell line. Conclusion:These results suggest that LINE-1 hypomethylation is common and may be linked to telomere shortening in WT.

Distribution of dystrophin gene deletions in a Chinese population

Objective To describe the deletion patterns and distribution characteristics of the dystrophin gene in a Chinese population of patients with Duchenne muscular dystrophy (DMD) or Becker muscular dystrophy (BMD). Methods Patients with DMD/BMD were recruited. Deletions in 19 exons of the dystrophin gene were evaluated using accurate multiplex polymerase chain reaction (PCR). Result Multiplex PCR identified deletions in 238/401 (59.4%) patients with DMD/BMD. Of these, 196 (82.4%) were in the distal hotspot, 32 (13.4%) were in the proximal hotspot, five (2.1%) were in both regions and five (2.1%) were in neither hotspot. Deletions were classified into 54 patterns. Exon 49 was the most frequently deleted. The reading frame rule was upheld for 91.9% of cases. Conclusion Accurate multiplex PCR for 19 exons is an effective diagnostic tool.

Association between serum soluble tumor necrosis factor-α receptors and early childhood obesity.

This study aimed to characterize the inflammatory cytokine profiles and further validate the significantly different cytokines in the serum obtained from obese children aged 36-48 months. Four obese children and four lean controls were randomly selected for inflammatory cytokine array assay, in which two cytokines [soluble tumor necrosis factor-α receptors (sTNFRs) 1 and 2] were found to be significantly different. Both cytokines (sTNFR1 and sTNFR2) were then further validated through enzyme-linked immunosorbent assay (ELISA) in 61 obese children and 52 lean children. ELISA results revealed that serum sTNFR1 level in obese children significantly increased (p = 0.003), whereas sTNFR2 did not change significantly (p = 0.069). Stratified analysis by gender showed that only obese girls presented increased sTNFR1 (p = 0.005) and sTNFR2 (p = 0.049) levels. We conclude that serum sTNFR1 is elevated in early childhood obesity. Moreover, serum sTNFR1 and sTNFR2 are associated with obese girls but not obese boys, thereby suggesting that serum sTNFRs in early childhood obesity may be sex related.