Multiple superovulations alter histone modifications in mouse early embryos

Abstract

It is demonstrated that repeated superovulation has deleterious effects on mouse ovaries and cumulus cells. However, little is known about the effects of repeated superovulation on early embryos. Epigenetic reprogramming is an important event in early embryonic development and could be easily disrupted by the environment. Thus, we speculated that multiple superovulations may have adverse effects on histone modifications in the early embryos. Female CD1 mice were randomly divided into four groups: (a) spontaneous estrus cycle (R0); (b) with once superovulation (R1); (c) with three times superovulation at a 7-day interval (R3) and (d) with five times superovulation at a 7-day interval (R5). We found that repeated superovulation remarkably decreased the fertilization rate. With the increase of superovulation times, the rate of early embryo development was decreased. The expression of Oct4, Sox2 and Nanog was also affected by superovulation in blastocysts. The immunofluorescence results showed that the acetylation level of histone 4 at lysine 12 (H4K12ac) was significantly reduced by repeated superovulation in mouse early embryos (P < 0.01). Acetylation level of histone 4 at lysine 16 (H4K16ac) was also significantly reduced in pronuclei and blastocyst along with the increase of superovulation times (P < 0.01). H3K9me2 and H3K27me3 were significantly increased in four-cell embryos and blastocysts. We further found that repeated superovulation treatment increased the mRNA level of histone deacetylases Hdac1, Hdac2 and histone methyltransferase G9a, but decreased the expression level of histone demethylase-encoding genes Kdm6a and Kdm6b in early embryos. In a word, multiple superovulations alter histone modifications in early embryos.

Dynamics of Known Long Non-Coding RNAs during the Maternal-to-Zygotic Transition in Rabbit

“…For instance, a study showed that combined PMSG and HCG did not alter the fertility ability of ovulated egg and the proportion of offspring obtained from 2-cell embryo transfer in rats [ 48 ]. While other study concluded that the ability of fertilized oocyte developing to embryo decreased after multiple gonadotropic stimulation [ 49 ]. Embryo development is mainly characterized by epigenetic re-programming.…”

“…Embryo development is mainly characterized by epigenetic re-programming. Gonadotropic stimulation can downregulate the acetylation level of histone 4 at lysine 12 (H4K12ac) in the early embryos [ 49 ]. Although superovulation causes average global DNA methylation changes of embryos in mice, additional experiment is needed to verify the result since they did not have repetitive samples [ 50 ].…”

A comparison study of superovulation strategies for C57BL/6J and B6D2F1 mice in CRISPR-Cas9 mediated genome editing

“…We compared the outcomes of using superovulated zygotes either from natural mating or IVF for producing GM mice by CRISPR-Cas9 technology. C57BL/6J mice were administrated with eCG-hCG or IAS-hCG and the mouse embryo development, which may result in the introduction of DNA methylation errors (Marshall and Rivera 2018;Tang et al 2019;Yu et al 2019). It is also reported that higher genome and Grb10 (an imprinted gene) methylation, and variable mRNA expression were observed during superovulation, together with reduced blastocyst cell numbers (Chen et al 2018).…”

Ovulation induction is associated with altered growth but with preservation of normal metabolic function in murine offspring

“…Although the agouti mouse is sensitive to environmental factors, the fact that we did not find differences in coat color after superovulation does not rule out the possibility that additional DNA methylation changes exist or that other imprinted loci might show abnormal methylation. For example, it has been shown that multiple rounds of superovulation may result in histone modifications of developing embryos (40). In addition, superovulation has been shown to alter imprinting marks in oocytes and embryos in a dose-dependent manner (10) because of abnormal methylation maintenance during preimplantation development (9).…”