title: Association of genomic instability, and the methylation status of imprinted genes and mismatch-repair genes, with neural tube defects.
abstract: 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 (Student's 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.
authors.affiliation: Department of Biochemistry, Capital Institute of Pediatrics, Beijing, China.
authors.forename: Zhuo
authors.initials: Z
authors.lastname: Liu
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Wang
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Li
authors.forename: Shengrong
authors.initials: S
authors.lastname: Ouyang
authors.forename: Huibo
authors.initials: H
authors.lastname: Chang
authors.forename: Ting
authors.initials: T
authors.lastname: Zhang
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Zheng
authors.forename: Jianxin
authors.initials: J
authors.lastname: Wu
mesh_terms: D020137:Base Pair Mismatch; D019175:DNA Methylation; D053843:DNA Mismatch Repair; D005260:Female; D018392:Genomic Imprinting; D042822:Genomic Instability / Q000235:genetics*; D006801:Humans; D007223:Infant; D008297:Male; D018895:Microsatellite Repeats; D009436:Neural Tube Defects / Q000235:genetics*