br Materials and Methods br Results br

Materials and Methods
Results
Discussion In our study, we were surprised to find that the transmission is limited to F1 generation. One possible explanation for the limited transmission for enhancement of LTP is that the phenotype ends at a younger age in the offspring of FSs rats than in their parents, such that it is no longer present and thus not transferable to offspring by the time the F1 generation are old enough to reproduce (Arai et al., 2009). But the phenomenon described here is clearly distinct from the studies described above. In our study, the enhancement in F0 generation maintained for at least 360days, within which the susceptibility of F2 generation were tested. Defining why the effect ends in F1 generation will require further experimentation. Traditional research on the combined effects of the environment and genetics on individual variation in disease risk highlighted the importance of genotype in human diseases. However, it is now becoming clear that a full understanding of environmental interactions with the genome will require epigenetic mechanisms (Anway & Skinner, 2006). Epigenetic changes encompass both DNA and orthopoxvirus variola modification, the most extensively studied is DNA methylation, which changes the chromatin packaging of DNA and finally inhibits gene expression (Feinberg, 2007). Our results showed that increased DNMT1 expression were induced by FSs. DNMT1 has preferential activity for hemimethylated DNA and is traditionally considered as a maintenance methyltransferase in DNA replication (Siedlecki & Zielenkiewicz, 2006). The increased DNMT1 may maintain the hyper-methylation status to the adult. Indeed, both of the seizure susceptibility and DNMT1expression in these two generations can be reversed by DNA methylation inhibitor. With the results presented here, we now found the existence of FSs induced changes in DNA methylation across one generation. Thus, our finding raises the intriguing speculation that some interventions, such as treatment with DNMT inhibitor, might be proved useful as therapeutic strategies for reversing persisting effects of FSs on both generations with enhancement in susceptibility. Notably, we found that enhanced susceptibility was passed on to the next generation through the mother, suggesting that the parents may differently influence the gene expression of offspring (Badcock & Crespi, 2008), which is consistent with the finding that transgenerational transmission of DNA methylation was through the mother. This phenomenon also exists in enriched environment induced enhancement of LTP (Arai et al., 2009). A possible explanation is that this transgenerational transmission of enhanced seizure susceptibility induced by FSs may be due to cytoplasmic inheritance, in which mitochondrial DNA played an important role (Luo et al., 2013). With regard to clinical significance, patients with epilepsy need to be asked not only whether they have relatives who suffer from epilepsy, but also whether patient\'s mother had experienced complex febrile convulsions. Therefore, these findings may affect the subsequent evaluation of patients with epilepsy.
Author Contributions D.C.W., B.F., and Y.J.D. performed most of the experiments, acquired most of the data presented, and performed the statistical analyses. Y.J.D., Y.S.T., and B.C. performed western blots and RT-PCR. C.L.X., S.W., K.W., S.H.Z., and B.Y.L. assisted with statistical analyses and in vivo electrophysiological recordings. D.C.W. and Z.C. designed experiments and co-wrote the manuscript. Z.C. supervised the research. All authors discussed the results and implications and commented on the manuscript at all stages.
Completing Financial Interests
Acknowledgements and Funding Sources This work was funded by the National Natural Science Foundation of China (91332202, 81630098, 81521062, and 81503045) and the Fundamental Research Funds for the Central Universities (2016QNA7015). We thank Dr. FD Shi (Tianjin Medical University General Hospital, China) and Dr. C Chen (Louisiana State University Health New Orleans Sciences Center, USA) for helpful discussions, and we are grateful to Dr. IC Bruce for reading the manuscript.