(CPP-CARM1) on the Cloned Mouse Embryonic Development
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www.nature.com/scientificreports OPEN The efect of cell penetrating peptide-conjugated coactivator-associated arginine Received: 23 May 2018 Accepted: 28 October 2018 methyltransferase 1 (CPP-CARM1) Published: xx xx xxxx on the cloned mouse embryonic development Jae-Il Bang 1, Eun-Hye Lee2, Ah Reum Lee1, Jin Il Lee 3, Seo Hye Choi1, Dong-Won Seol1, Chang-Hwan Park2 & Dong Ryul Lee 1,4 Abnormalities in gene expression that negatively afect embryonic development are frequently observed in cloned embryos generated by somatic cell nuclear transfer (SCNT). In the present study, we successfully produced a cell-penetrating peptide (CPP)-conjugated with coactivator-associated arginine methyltransferase 1 (CARM1) protein from mammalian cells and confrmed introduction into donor somatic cells and cloned 8-cell embryos within 3 hours after addition to culture medium. In addition, H3R17 dimethylation and embryonic development up to the blastocyst stage were increased in the group treated with exogenous CPP-CARM1 protein compared with the untreated group (control). Interestingly, the number of total cells and trophectoderm in blastocysts as well as implantation rate were signifcantly increased in the CPP-CARM1 protein-treated group. However, the cell number of inner cell mass (ICM) was not changed compared with the control group; similarly, expression of pluripotency-related genes Oct4 and Nanog (ICM markers) was not signifcantly diferent between groups. On the other hand, expression of the implantation-related gene Cdx2 (trophectoderm marker) was transiently increased after treatment with CPP-CARM1 protein. On the basis of these results, we conclude that supplementation with exogenous CPP-CARM1 protein improves embryonic development of cloned embryos through regulation of histone methylation and gene expression. In addition, our results suggest that CPP-CARM1 protein may be a useful tool for strengthening implantation of mammalian embryos. Somatic cell nuclear transfer (SCNT) is the process by which the cytoplasm of a recipient oocyte reprograms a nucleus from a diferentiated somatic donor cell, resulting in the production of cloned embryos with the genetic information of the donor cell. Tis technique was frst described for the embryonic development of Xenopus in a report by Gurdon1. Subsequent research has confrmed that fully diferentiated somatic cells are capable of cell-fate switching through reprogramming1. Since the study of Gurdon, SCNT technology has successfully pro- duced animals from cloned embryos of various species of mammals2–4. However, poor quality of developmental patterns attributable to reduced cell number and altered gene expression were frequently observed in most cloned embryos compared with in vivo- and in vitro-fertilized embryos5. To overcome this problem, researchers have sought to produce improved cloned embryos through supplementation of the culture medium with chemical reagents6–8 and growth factors9,10. 1Department of Biomedical Science, CHA University, Seongnam, 13488, Korea. 2Graduate School of Biomedical Science and Engineering, Hanyang University, Seoul, 04763, Korea. 3Fertility Center of CHA Gangnam Medical Center, College of Medicine, CHA University, Seoul, 06135, Korea. 4CHA Stem Cell Institute, CHA University, Seongnam, 13488, Korea. Jae-Il Bang and Eun-Hye Lee contributed equally. Correspondence and requests for materials should be addressed to C.-H.P. (email: [email protected]) or D.R.L. (email: [email protected]) SCIENTIFIC REPORTS | (2018) 8:16721 | DOI:10.1038/s41598-018-35077-0 1 www.nature.com/scientificreports/ A number of epigenetic strategies for manipulating embryonic development without changing gene sequences have recently been investigated11–13, some of which have been applied to the production of cloned embryos14,15. Previous studies reported that application of the histone modifying enzymes, lysine (K)-specifc demethylase 4D (KDM4D) to cloned mouse embryos overcame epigenetic barriers to embryo development at the 2-cell stage through elimination of H3K9 methylation of donor somatic cells; treatment of human embryos with the KDM4A isoform acted through a similar mechanism to overcome barriers at the 4- to 8-cell stage14,15. One histone mod- ifying enzyme, coactivator-associated arginine methyltransferase 1 (CARM1), also known as protein arginine N-methyltransferase 4 (PRMT4), act in conjunction with other transcription factors, such as P53, NFkB, LEF1/ TCF4 and TIF1a, to control gene expression16–18. CARM1 has also been shown to directly methylate histone 3 at arginine 2, 17 and 26 to control gene expression. Zernicka-Goetz and colleagues reported that endogenous CARM1 is involved in determining the fate of cells in 2-cell-stage embryos by inducing histone H3Arg26 (H3R26) dimethylation13. In embryonic stem cell (ESC) studies, CARM1 was shown to enhance the pluripotency of stem cells by increasing the expressions of Oct4 (octamer-binding transcription factor 4), Sox2 (SRY box 2), and Nanog (Nanog homeobox) genes19. In addition, increasing dimethylated H3R17 (H3R17me2) in human mesenchymal stem cells (MSCs) by treatment with CARM1 was shown to improve the expression of stemness-related genes and enhance diferentiation-efciency into mesodermal lineage cells20. However, the efect of treatment with exogenous CARM1 protein on pre- or post-implantation embryonic development has still not been well studied. For epigenetic modifcation of an oocyte or embryo, mRNA, small interfering RNA (siRNA), or protein are typically injected into the cytoplasm through micromanipulation. However, this procedure is technically demanding and is likely to cause physical damage to the cloned embryo14,15. To avoid those limitations, many researchers have sought more facile and efective techniques for delivering verifed factors into cells and embryos. It was recently reported that induced pluripotent cells (iPSCs) could be generated by introducing transcription factors fused with a cell-penetrating peptide (CPP)21,22. Lim and colleagues also identifed a new form of CPP, obtained from human papillomavirus L1 capsid protein (LDP12), and confrmed its ability to deliver a fusion protein of enhanced green fuorescence protein and MAP1LC3 (EGFP-LC3) into mouse blastocysts23. In our previously reports, the cell number of inner cell mass (ICM) and expression of the Oct4 gene were positively regulated in fresh and cryopreserved embryos afer treatment with CPP-conjugated estrogen-related receptor β (CPP-ESRRB) during in vitro cultivation24,25. In the present study, we provide the frst demonstration that exog- enous supplementation with a novel CPP-conjugated CARM1 improves the normally poor embryonic develop- ment of cloned mouse embryos through regulation of gene expression. Results Construction of novel CPP-conjugated DsRed2 and CARM1 expression vectors. Expression vec- tors designed to produce recombinant CPP-CARM1 and CPP-DsRed2 (internal control) proteins are shown in Fig. 1A. To enable efcient delivery of recombinant proteins, we fused a CPP (KRK) sequence to the C-terminus of each protein; purifcation was facilitated by incorporating a FLAG- and His6-tag at the C-terminal end of DsRed2- and CARM1-constructs (Fig. 1A). Te purifed recombinant proteins were confrmed by Western blot analysis using an anti-FLAG antibody. Te size of CPP-DsRed2 and CPP-CARM1 proteins were approximately 30 and 70 kDa, respectively (Figs 1B and S1). Te concentration of purifed CPP-proteins was determined (Fig. S2) and adjusted to 20 µg/mL. Delivery of CPP-DsRed2 and CPP-CARM1 proteins into somatic cells and manipulated embryos. In a preliminary experiment, we examined the delivery of CPP-DsRed2 and CPP-CARM1 proteins into mouse cumulus cells (donor nuclei for nuclear transfer) and embryos by adding these proteins to culture medium at a 1:5 ratio (fnal concentration to 4 µg/mL). As shown in Fig. 1C, these proteins were frst detected in all cumulus cells afer 3 hours, but no morphological changes were observed in treated or untreated cells. We next analyzed the efect of CPP-conjugated protein treatment of nuclear donor cells (cumulus cells) on the development of SCNT mouse embryos. Cloned embryos obtained using CPP-CARM1-treated donor cells (CARM1-DSCNT group) showed an increase in 2-cell formation rate compared with that for CPP-DsRed2-treated donor cells (DsRed2-DSCNT group) (85.7 ± 1.3 vs. 77.8 ± 2.5, p < 0.05), but further development revealed no signifcant diference in blastocyst formation rate between the two groups (Table S2). In our preliminary study, we injected the Carm1 mRNA into cloned mouse embryos afer chemical activation (at 1-cell stage) and investigated their embryonic development. Te developmental rate to 2-cell stage was increased in the Carm1 mRNA-injected group compared to Sham injection group (p < 0.05), but blastocyst development of the Carm1 mRNA-injected group was not diferent to that of the SCNT group and sham injection group, respectively (Table S3, p > 0.05). In addition, from the previously reports, overexpression of CARM1 in 4-cell embryo is involved in determination of the fate in embryonic blastomeres and of cell polarity in the development of preimplantation embryo13,26. So, in the present study, we have investigated the efect of CARM1-treatment on the cloned mouse embryonic develop- ment at the 8-cell stage (afer decision of embryonic fate). Improved development of cloned embryos after supplementation with CPP-CARM1 pro- tein. To avoid changes of embryonic cell fate determined by endogenous CARM1 expression