Effects Of Fluoride On Germ Cell Structure And DNA Methylation Of Early Fertilization Embryos In Mice

During the process of mammalian genetic modification of regulation, DNA methylation is an important way. In the whole development process of the embryo, DNA methylation has experienced a dynamic reprogramming within the scope of the whole genome. Imprinted gene main function is to play the role of the growth of embryos and its development, embryo imprinting function disorder leads to abnormal embryonic development and even death. Tissue damage and reproductive toxicity caused by fluorosis is currently a hot research topic. DNA methylation status plays an important role in maintaining normal levels of methylation. The adverse effect of fluoride on embryonic development and its teratogenic and carcinogenic effects on the reproductive system have certain association with DNA methylation. Fluoride and its compound has significant genetic toxicity, but the specific mechanism is unclear. This study was conducted to investigate the effects of fluoride on cell ultrastructure changes of mouse hypothalamus, pituitary, testis, and genomic DNA methylation and imprinting gene DNA methylation in mouse early embryos. The epigenetics is introduced to study the reproductive toxicity of fluoride. Main results were as following:1. Results of effects of fluoride on cell ultrastructure changes of mouse hypothalamus, pituitary and testis showed that damages with different degrees in the treatment group were observed in these organs under the optical microscope and transmission electron microscope. High fluorine group had severe damage.2. The effects of fluoride on DNA methylation of early fertilization embryos were observed through early pregnant mice. To understand the effects, female mice were fed with fluorine-containing water for 2 days, then DNA methylation of the imprinted genes and retrotransposon LINE1 gene in the embryo were examined using BSP and COBRA techniques. The concentration of fluoride was not enough to interfere with the stability of the whole genome DNA methylation, only the imprinted gene H19 was more sensitive to its influence.3. Effects of male mice intake of fluoride on DNA methylation in the early fertilization embryos was examined. Results showed that DNA methylation level of H19 in the treatment group(44.38%±5.77%) was significantly reduced than that in control group(10.71.% ±3.54%); DNA methylation level of Kv DMR1 in the treatment group(63.89.%±11.72%) was significantly reduced than that in control group(5.48.%±0.32%) too. Same situation was also seen in DNA methylation level of Peg3 between the treatment group(95.89%±17.72%) and the control group(4.08%±0.43%). The difference of DNA methylation level of LINE1 between the treatment group and the control group was not seen. This results suggested that DNA methylation of the imprinted genes(HI9, Peg3, Kv DMR1) increased significantly, while the difference of DNA methylation of the LINE1 gene was not seen.