During germ cell development in mouse de novo Dnmts
During germ cell development in mouse, de novo Dnmts regulate the genomic imprinting and silence of repeat elements. Dnmt3A methylated H19, Dlk1/Gtl2, and Sine B1, whereas Dnmt3B methylated microsatellite repeat elements, the two Dnmts co-methylatedRasgrf1, IAP, and Line1 repeat elements (Lucifero et al., 2007). Also, Dnmt3L−/− leads to meiotic catastrophe via retrotransposon reactivation in male germ Maraviroc (Bourchis and Bestor, 2004). To address the role of dnmt3 in meiotic progression, this study focused on the meiotic gene regulation. Msh4, a homologue of the bacterial mismatch repair protein MutS, forms a heterodimer with Msh5 to stabilize branched DNA structures, thus playing an important role in homologous pairing and recombination at leptotene and zygotene stages, which occurs one stage before chromosome synapsis at the pachytene stage (Kneitz et al., 2000; Snowden et al., 2004) and initiates presynaptic alignment (Storlazzi et al., 2010). Epigenetic modifications seem to allow an organism to respond to different environment and physiological disorder through changes in gene expression (Jaenisch and Bird, 2003). In this paper, we found that msh4 increased abnormally and dnmt3 decreased in sterile triploid when compared with fertile diploid and allotetraploid. Moreover, when E2 treatment increased the dnmt3 expression, the expression of msh4 decreased. We also detected the variation of DNA methylation level of the first exon of msh4. Based on these results, we proposed that msh4 expression is regulated by dnmt3, which is correlated with sterility regulation. E2 treatment in 3n fish increased whole genomic DNA methylation level, which is consistent with the phenomenon in stickleback (Aniagu et al., 2008). As related to the exact gene, E2 treatment increased the exon CGI methylation level, and decreased the expression of msh4. This similar effect of E2 on msh4 has been reported in mammals (Singh et al., 2012).
In conclusion, our studies identified the dnmt3 gene sequence and characterized the role of this gene in regulating reproductive fertility in fish. Dnmt3 was under E2 control and its regulation in meiotic pachytene impairment of oocytes in 3n fish might be correlated with the exon CGI methylation and gene expression of msh4. Our results elucidated the epigenetic mechanism of dnmt3 regulating sterility in female 3n fish for the first time, and played a significant role in reproductive biology in theory and in aquaculture breeding in practice.
Acknowledgements Our work was supported in whole or part by the National Natural Science Foundation of China, China (31402297, 31430088, 31702328); the Earmarked fund for China Agriculture Research System, China (CARS-45); Natural Science Foundation of Hunan Province, China Grants (2018JJ3338); Hunan Provincial Natural Science and Technology Major Project, China (2017NK1031); Cooperative Innovation Center of Engineering and New Products for Developmental Biology of Hunan Province, China (20134486).
Introduction DNA methyltransferase (MTase) is a primary epigenetic modification enzyme that catalyzes the DNA methylation by transferring a methyl group to the target adenine or cytosine residue from donor S-adenosyl-L-methionine (SAM) , , , . It plays an essential role in regulating gene expression and maintaining genomic stability , , . Abnormal DNA MTase activity is strongly associated with tumorigenesis by silencing transcription of gene expression and inactivating tumor suppressor gene , . Also, studies show that DNA MTase activity is directly linked with DNA methylation level, and the DNA methylation level can evince the abnormality much earlier than other signs of malignancy . DNA MTase has thus been considered as a promising biomarker for cancer diagnosis and a potential therapeutic target for cancer therapy , , , . DNA MTase activity detection in a sensitive and specific way should contribute to resolving its related function in cancer initiation and exploring its possible application in cancer theranostics.