title: Spatiotemporal dynamics of OCT4 protein localization during preimplantation development in mice.
abstract: Spatiotemporal expression of transcription factors is crucial for genomic reprogramming. Pou5f1 (Oct4) is an essential transcription factor for reprogramming. A recent study reported that OCT4A, which is crucial for establishment and maintenance of pluripotent cells, is expressed in oocytes, but maternal OCT4A is dispensable for totipotency induction. Whereas another study reported that OCT4B, which is not related to pluripotency, is predominantly expressed instead of OCT4A during early preimplantation phases in mice. To determine the expression states of OCT4 in murine preimplantation embryos, we conducted in-depth expression and functional analyses. We found that pluripotency-related OCT4 mainly localizes to the cytoplasm in early preimplantation phases, with no major nuclear localization until the 8-16-cell stage despite high expression in both oocytes and early embryos. RNA-sequencing analysis using oocytes and early preimplantation embryos could not identify the splice variants creating alternative forms of OCT4 protein. Forced expression of OCT4 in zygotes by the injection of polyadenylated mRNA clearly showed nuclear localization of OCT4 protein around 3-5-fold greater than physiological levels and impaired developmental competency in a dose-dependent manner. Embryos with modest overexpression of OCT4 could develop to the 16-cell stage; however, more than 50% of the embryos were arrested at this stage, similar to the results for OCT4 depletion. In contrast, extensive overexpression of OCT4 resulted in complete arrest at the 2-cell stage accompanied by downregulation of zygotically activated genes and repetitive elements related to the totipotent state. These results demonstrated that OCT4 protein localization was spatiotemporally altered during preimplantation development, and strict control of Oct4 protein levels was essential for proper totipotential reprogramming.
authors: Center for Regenerative MedicineNational Research Institute for Child Health and Development, Setagaya, Tokyo, Japan.
authors: Atsushi
authors: A
authors: Fukuda
authors: Center for Regenerative MedicineNational Research Institute for Child Health and Development, Setagaya, Tokyo, Japan.
authors: Atsushi
authors: A
authors: Mitani
authors: Department of Molecular GeneticsKitasato University Graduate School of Medical Sciences, Minami, Sagamihara, Kanagawa, Japan.
authors: Toshiyuki
authors: T
authors: Miyashita
authors: NODAI Genome Research CenterTokyo University of Agriculture, Setagaya-ku, Tokyo, Japan.
authors: Hisato
authors: H
authors: Kobayashi
authors: Center for Regenerative MedicineNational Research Institute for Child Health and Development, Setagaya, Tokyo, Japan.
authors: Akihiro
authors: A
authors: Umezawa
authors: Center for Regenerative MedicineNational Research Institute for Child Health and Development, Setagaya, Tokyo, Japan Department of Stem Cell ResearchFukushima Medical University, 1 Hikarigaoka, Fukushima City, Fukushima, Japan akutsu-h@ncchd.go.jp.
authors: Hidenori
authors: H
authors: Akutsu
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000166:cytology* / Q000378:metabolism; D004622:Embryo, Mammalian / Q000166:cytology* / Q000378:metabolism; D047108:Embryonic Development / Q000235:genetics*; D053595:Embryonic Stem Cells / Q000166:cytology* / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D008297:Male; D051379:Mice; D050814:Octamer Transcription Factor-3 / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D011247:Pregnancy; D062211:Spatio-Temporal Analysis
chemical_list: D050814:Octamer Transcription Factor-3; C494174:Pou5f1 protein, mouse