title: Reconstruction of mouse oocytes by germinal vesicle transfer: maturity of host oocyte cytoplasm determines meiosis.
abstract: We evaluated the maturational competence of mouse oocytes reconstructed by the transfer and electrofusion of germinal vesicles (GV) into anuclear cytoplasts of GV stage oocytes (both auto- and hetero-transfers), metaphase II stage oocytes or zygotes. Following in-vitro culture, the maturation rates of the reconstructed oocytes to metaphase II did not significantly differ between auto- and hetero-transfers (40/70 versus 95/144 respectively); these rates also did not differ from those of control oocytes (57/97) which were matured in vitro without micromanipulation and electrofusion. In contrast, when a GV was transferred into an enucleated metaphase II oocyte or a zygote, only a few reconstructed oocytes underwent germinal vesicle breakdown (5/30 and 2/21 respectively); moreover, none reached metaphase II stage. Cytogenetic and immunofluorescence analyses were conducted on hetero-GV oocytes that extruded a first polar body. Each oocyte showed two groups of chromosomes, one in the cytoplast and one in the polar body, as well as a bipolar spindle with twenty univalent chromosomes. Our findings suggest that oocytes reconstructed by GV transfer into a cytoplast of the same developmental stage mature normally in vitro through metaphase II. Such oocytes may be a useful research model to elucidate the cytoplasmic and nuclear mechanisms regulating meiosis and the relationships between meiotic errors and age-related changes in the oocyte.
authors.affiliation: Department of Obstetrics and Gynecology, New York University Medical Center, 660 First Avenue, Fifth Floor, New York, NY 10016, USA.
authors.forename: H
authors.initials: H
authors.lastname: Liu
authors.forename: C W
authors.initials: CW
authors.lastname: Wang
authors.forename: J A
authors.initials: JA
authors.lastname: Grifo
authors.forename: L C
authors.initials: LC
authors.lastname: Krey
authors.forename: J
authors.initials: J
authors.lastname: Zhang
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000008:administration & dosage; D000818:Animals; D002467:Cell Nucleus / Q000502:physiology; D003593:Cytoplasm / Q000502:physiology*; D005260:Female; D008540:Meiosis; D008677:Metaphase; D051379:Mice; D053652:Nuclear Transfer Techniques; D009865:Oocytes / Q000648:ultrastructure*; D013997:Time Factors; D015053:Zygote / Q000648:ultrastructure
chemical_list: D015056:1-Methyl-3-isobutylxanthine