title: Nuclear reprogramming by interphase cytoplasm of two-cell mouse embryos.
abstract: Successful mammalian cloning using somatic cell nuclear transfer (SCNT) into unfertilized, metaphase II (MII)-arrested oocytes attests to the cytoplasmic presence of reprogramming factors capable of inducing totipotency in somatic cell nuclei. However, these poorly defined maternal factors presumably decline sharply after fertilization, as the cytoplasm of pronuclear-stage zygotes is reportedly inactive. Recent evidence suggests that zygotic cytoplasm, if maintained at metaphase, can also support derivation of embryonic stem (ES) cells after SCNT, albeit at low efficiency. This led to the conclusion that critical oocyte reprogramming factors present in the metaphase but not in the interphase cytoplasm are 'trapped' inside the nucleus during interphase and effectively removed during enucleation. Here we investigated the presence of reprogramming activity in the cytoplasm of interphase two-cell mouse embryos (I2C). First, the presence of candidate reprogramming factors was documented in both intact and enucleated metaphase and interphase zygotes and two-cell embryos. Consequently, enucleation did not provide a likely explanation for the inability of interphase cytoplasm to induce reprogramming. Second, when we carefully synchronized the cell cycle stage between the transplanted nucleus (ES cell, fetal fibroblast or terminally differentiated cumulus cell) and the recipient I2C cytoplasm, the reconstructed SCNT embryos developed into blastocysts and ES cells capable of contributing to traditional germline and tetraploid chimaeras. Last, direct transfer of cloned embryos, reconstructed with ES cell nuclei, into recipients resulted in live offspring. Thus, the cytoplasm of I2C supports efficient reprogramming, with cell cycle synchronization between the donor nucleus and recipient cytoplasm as the most critical parameter determining success. The ability to use interphase cytoplasm in SCNT could aid efforts to generate autologous human ES cells for regenerative applications, as donated or discarded embryos are more accessible than unfertilized MII oocytes.
authors.affiliation: Division of Reproductive and Developmental Sciences, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006, USA.
authors.forename: Eunju
authors.initials: E
authors.lastname: Kang
authors.affiliation: Max Planck Institute for Molecular Biomedicine, Münster 48149, Germany.
authors.forename: Guangming
authors.initials: G
authors.lastname: Wu
authors.affiliation: Division of Reproductive and Developmental Sciences, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Ma
authors.affiliation: Division of Reproductive and Developmental Sciences, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.affiliation: Division of Reproductive and Developmental Sciences, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006, USA.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Tippner-Hedges
authors.affiliation: 1] Division of Reproductive and Developmental Sciences, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006, USA [2] South Miyagi Medical Center, Miyagi 989-1253, Japan.
authors.forename: Masahito
authors.initials: M
authors.lastname: Tachibana
authors.affiliation: Division of Reproductive and Developmental Sciences, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006, USA.
authors.forename: Michelle
authors.initials: M
authors.lastname: Sparman
authors.affiliation: Division of Reproductive and Developmental Sciences, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006, USA.
authors.forename: Don P
authors.initials: DP
authors.lastname: Wolf
authors.affiliation: Max Planck Institute for Molecular Biomedicine, Münster 48149, Germany.
authors.forename: Hans R
authors.initials: HR
authors.lastname: Schöler
authors.affiliation: Division of Reproductive and Developmental Sciences, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006, USA.
authors.forename: Shoukhrat
authors.initials: S
authors.lastname: Mitalipov
mesh_terms: D000818:Animals; D002452:Cell Count; D065150:Cellular Reprogramming; D019976:Cloning, Organism; D003593:Cytoplasm / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000166:cytology*; D053595:Embryonic Stem Cells / Q000166:cytology*; D005260:Female; D057026:Induced Pluripotent Stem Cells / Q000166:cytology*; D007399:Interphase; D008297:Male; D008677:Metaphase; D051379:Mice; D053652:Nuclear Transfer Techniques