[The role of insulin-like growth factor-2 gene differentially methylated regions in TCDD-induced malformation].
OBJECTIVE
To study the effects of 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) on the development of fetal rats and to explore the relationship between TCDD-induced abnormal development in rats and the expression and the methylation of insulin-like growth factor 2 gene (Igf2).


METHODS
A single dose of 10 microg/kg TCDD was given to gestation day (GD) 10 pregnant rats by gavage. On GD20, the fetuses were taken out and examined. The crown-rump length, the body weight and the placental weight were measured. The expression of Igf2 in liver was detected by real-time quantitative reverse transcription (RT-PCR) and Western blot. The methylation of Igf2 differentially methylated regions (DMRs) in liver was analyzed by a methylation-sensitive restriction enzyme Hpa II PCR assay and a bisulfite-modified DNA sequencing procedure.


RESULTS
In the treatment group, 12.2% of the fetuses were either dead or absorbed, and 11.6% of them were malformed. For the live fetuses, their crown-rump length, body weight and placental weight were significantly lower than those of the control group. The relative amount of Igf2 mRNA in the treated livers and the control livers was 0.77 +/- 0.11 and 0.27+/- 0.15, respectively. The number was significantly higher in the treatment group than in the control group (P < 0.01). Western blot also showed a remarkable up regulation of Igf2 protein in liver after treatment. The two groups showed no difference in the methylation status of Igf2 DMR1 in liver. The DMR2 Igf2 was significantly hypomethylated in the treated livers than in the control livers.


CONCLUSIONS
Exposure to TCDD in pregnancy can lead fetal rats to death, absorption, malformation and intrauterine growth retardation (IUGR). The TCDD led abnormal development in rats may be associated with the hypomethylated DMR2 of Igf2 and the up regulation of Igf2 in liver.
Wang
Jun
J
Department of Medical Genetics, China Medical University, Shenyang, Liaoning, 110001 PR China.
Zhao
Yan-yan
YY
Liu
Hong
H
Li
Ying-hui
YH
Li
Guang-yu
GY
Sun
Kai-lai
KL
Guo
Lei
L
D000818:Animals; D015153:Blotting, Western; D019175:DNA Methylation; D005260:Female; D005317:Fetal Growth Retardation / Q000139:chemically induced / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D007335:Insulin-Like Growth Factor II / Q000235:genetics* / Q000378:metabolism; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity*; D011247:Pregnancy; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D007335:Insulin-Like Growth Factor II