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Objective: To investigate global DNA methylation and DNA methyhransferases participation in the mechanism of cleft palate induced by maternal exposure to 2,3,7,8-tetrachlrodibenzo-p-dioxin (TCDD)in mice., Methods: 40 pregnant C57BL/6J mice were randomly divided into 2 groups: the control group(n =20) and TCDD-exposure group(n =20).On gestation day 10.5 (GD10.5),the mice in TCDD-group were orally administrated with TCDD 28 μg/kg, while the mice in the control group received equivalent corn oil. The pregnant mice were sacrificed on GD13.5,GD14.5,GD15.5,GD16.5,GD17.5,fetal palates were collected for analysis. Global DNA methylation levels were detected by Methylamp TM Global DNA Methylation Quantification Ultra Kit through an ELISA-like reaction. The expression levels of DNA methyltransferases were examined by quantitative real-time PC R(q-PCR).IBM SPSS 20.0 software was applied for statistical analysis. Kolmogorov-Smirnov test was used for normal distribution check, and the distribution was normal. Independent t-test was carried out among two groups. P ＜ 0.05 was considered statistically significant., Results: The global DNA methylation level in TCDD-exposure group was significantly higher than that in control group on GD13.5 (49.52％ ±4.03％ vs 33.42％ ± 6.78％,P ＜ 0.01),while lower on GD14.5 (24.10％ ±2.29％ vs 30.12％ ±3.92％,P ＜0.05) and on GD16.5 (32.77％ ±0.98％ vs 36.45％ ± 3.27％,P ＜ 0.05).The expression level of Dnmt1 mRNA in TCDD-exposure group was higher than that in control group on GD13.5(1.28±0.11 vs 1.01 ±0.10,P＜0.05) and on GD16.5(1.04 ±0.05 vs 0.81 ±0.01,P ＜0.01).The expression level of Dnmt3a mRNA in TCDD-exposure group was higher than that in control group on GD13.5 (1.15 ±0.17 vs 0.81 ±0.02,P ＜0.05)and on GD16.5 (1.11 ± 0.06 vs 0.96 ± 0.06,P ＜ 0.05).The expression level of Dnmt3b mRNA in TCDD-exposure group was higher than that in control group on GD14.5(0.97 ±0.06 vs 0.72 ±0.06,P ＜0.01)., Conclusions: It is supposed that complicated mechanisms are exist to regulate global DNA methylation levels in palatal tissue of fetal mice. The significant increased DNA methylation level on GD13.5 resulting from up-expression of Dnmt1 and Dnmt3a may be one of the epigenetic mechanisms which cause palate malformation in fetal mice induced by maternal exposure to TCDD.

Background: Diabetic nephropathy is a complex disease with poor outcomes, and our current treatment measures are limited. It is urgent to search for novel therapeutic targets. Recently, a mesangium-predominant gene, megsin, has emerged as a participant in mesangial cell proliferation and/or mesangial matrix expansion. This study investigated the effect of megsin down-regulation on the progression of diabetic nephropathy., Methods: Streptozotocin (STZ)-induced diabetic CD-1 mice after uninephrectomy received a pBAsi mU6 Neo megsin siRNA plasmid for 12 weeks and were compared with age-matched nondiabetic mice. In vitro mouse mesangial cells were transfected with pBAsi mU6 Neo megsin siRNA plasmid using Lipofectamine 2000 reagent and further cultured in DMEM containing high glucose for up to 48 hours. All of the cells were collected for protein extraction and the supernatant for type IV collagen measurement. The expression of megsin, matrix metalloproteinase-2 (MMP-2), tissue inhibitor of metalloproteases-2 (TIMP-2) and p27(Kip1) was determined by Western blotting., Results: The megsin siRNA plasmid alleviated proteinuria and glomerular type IV collagen accumulation 12 weeks after the STZ injection, down-regulated renal cell proliferation and normalized the imbalance between MMP-2 and TIMP-2. Also, in vitro experiments showed that the glomerular mesangial cellular proliferation and type IV collagen production induced by high glucose were relieved after the transfection of megsin siRNA plasmid. The level of p27(kip1) was down-regulated in transfected mesangial cells significantly., Conclusions: The study suggests that the down-regulation of megsin might exert beneficial effects on the diabetic kidney partly through down-regulation of p27(kip1) level and that megsin may serve as a novel therapeutic target in the management of diabetic nephropathy.