title: Merotelic attachments allow alignment and stabilization of chromatids in meiosis II oocytes.
abstract: The chromosome segregation process in human oocytes is highly error-prone, generating meiosis II (MII) oocytes with unbalanced chromatids that contribute to aneuploidy in offspring. This raises questions regarding the mechanism for transmission of chromatids and how chromatids evade the error correction mechanisms in MII oocytes. Here, we analyse the behaviour of chromatids in mouse MII oocytes. We find that chromatids align at the spindle equator at the metaphase stage of MII and that their presence does not obstruct entry into the anaphase stage. The alignment process is mediated by merotelic (bi-directional) microtubule-kinetochore attachments, revealing a multi-domain organization of the kinetochore of mammalian meiotic chromosomes. Our results suggest that biorientation of chromatids stabilize microtubule attachments at the kinetochores in a tension-dependent manner. Our results also suggest that merotelic attachments contribute to chromosome mis-segregation in wild-type MII oocytes. Thus, merotely is an important promoter of aneuploidy in mammalian oocytes.
authors.affiliation: Department of Cell and Molecular Biology, Karolinska Institutet, Berzelius väg 35, 171 77 Stockholm, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Kouznetsova
authors.affiliation: Department of Cell and Molecular Biology, Karolinska Institutet, Berzelius väg 35, 171 77 Stockholm, Sweden.
authors.forename: Abrahan
authors.initials: A
authors.lastname: Hernández-Hernández
authors.affiliation: Department of Cell and Molecular Biology, Karolinska Institutet, Berzelius väg 35, 171 77 Stockholm, Sweden.
authors.forename: Christer
authors.initials: C
authors.lastname: Höög
mesh_terms: D000705:Anaphase / Q000502:physiology; D000818:Animals; D018797:Cell Cycle Proteins; D002842:Chromatids / Q000502:physiology*; D020090:Chromosome Segregation / Q000502:physiology; D004268:DNA-Binding Proteins; D005260:Female; D018386:Kinetochores / Q000502:physiology*; D008540:Meiosis / Q000502:physiology*; D008677:Metaphase / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008870:Microtubules / Q000502:physiology*; D023421:Models, Animal; D009687:Nuclear Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D008941:Spindle Apparatus / Q000502:physiology
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C490062:Sycp3 protein, mouse