title: Dynamic assembly of brambleberry mediates nuclear envelope fusion during early development.
abstract: To accommodate the large cells following zygote formation, early blastomeres employ modified cell divisions. Karyomeres are one such modification, mitotic intermediates wherein individual chromatin masses are surrounded by nuclear envelope; the karyomeres then fuse to form a single mononucleus. We identified brambleberry, a maternal-effect zebrafish mutant that disrupts karyomere fusion, resulting in formation of multiple micronuclei. As karyomeres form, Brambleberry protein localizes to the nuclear envelope, with prominent puncta evident near karyomere-karyomere interfaces corresponding to membrane fusion sites. brambleberry corresponds to an unannotated gene with similarity to Kar5p, a protein that participates in nuclear fusion in yeast. We also demonstrate that Brambleberry is required for pronuclear fusion following fertilization in zebrafish. Our studies provide insight into the machinery required for karyomere fusion and suggest that specialized proteins are necessary for proper nuclear division in large dividing blastomeres.
authors.affiliation: Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, 1211 BRB II/III, 421 Curie Boulevard, Philadelphia, PA 19104-6058, USA.
authors.forename: Elliott W
authors.initials: EW
authors.lastname: Abrams
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
authors.forename: Florence L
authors.initials: FL
authors.lastname: Marlow
authors.forename: Lee
authors.initials: L
authors.lastname: Kapp
authors.forename: Sumei
authors.initials: S
authors.lastname: Lu
authors.forename: Mary C
authors.initials: MC
authors.lastname: Mullins
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001757:Blastomeres / Q000378:metabolism; D002453:Cell Cycle; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism*; D005260:Female; D006801:Humans; D007313:Insecta / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D008297:Male; D008322:Mammals / Q000196:embryology / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D009685:Nuclear Envelope / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D016415:Sequence Alignment; D008941:Spindle Apparatus / Q000378:metabolism; D015027:Zebrafish / Q000196:embryology* / Q000378:metabolism; D029961:Zebrafish Proteins / Q000378:metabolism*; D015053:Zygote / Q000166:cytology / Q000378:metabolism
chemical_list: C109412:KAR5 protein, S cerevisiae; D008565:Membrane Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D029961:Zebrafish Proteins; C575716:p22atuz protein, zebrafish