title: The endoplasmic reticulum is partitioned asymmetrically during mitosis before cell fate selection in proneuronal cells in the earlyDrosophilaembryo.
abstract: Asymmetric cell division is the primary mechanism to generate cellular diversity, and it relies on the correct partitioning of cell fate determinants. However, the mechanism by which these determinants are delivered and positioned is poorly understood, and the upstream signal to initiate asymmetric cell division is unknown. Here we report that the endoplasmic reticulum (ER) is asymmetrically partitioned during mitosis in epithelial cells just before delamination and selection of a proneural cell fate in the earlyDrosophilaembryo. At the start of gastrulation, the ER divides asymmetrically into a population of asynchronously dividing cells at the anterior end of the embryo. We found that this asymmetric division of the ER depends on the highly conserved ER membrane protein Jagunal (Jagn). RNA inhibition ofjagnjust before the start of gastrulation disrupts this asymmetric division of the ER. In addition,jagn-deficient embryos display defects in apical-basal spindle orientation in delaminated embryonic neuroblasts. Our results describe a model in which an organelle is partitioned asymmetrically in an otherwise symmetrically dividing cell population just upstream of cell fate determination and updates previous models of spindle-based selection of cell fate during mitosis.
authors.affiliation: Department of Biology, San Francisco State University, San Francisco, CA 94132.
authors.forename: Anthony S
authors.initials: AS
authors.lastname: Eritano
authors.affiliation: Department of Biology, San Francisco State University, San Francisco, CA 94132.
authors.forename: Arturo
authors.initials: A
authors.lastname: Altamirano
authors.affiliation: Department of Biology, San Francisco State University, San Francisco, CA 94132.
authors.forename: Sarah
authors.initials: S
authors.lastname: Beyeler
authors.affiliation: Department of Biology, San Francisco State University, San Francisco, CA 94132.
authors.forename: Norma
authors.initials: N
authors.lastname: Gaytan
authors.affiliation: Department of Biology, San Francisco State University, San Francisco, CA 94132.
authors.forename: Mark
authors.initials: M
authors.lastname: Velasquez
authors.affiliation: Department of Biology, San Francisco State University, San Francisco, CA 94132 riggs@sfsu.edu.
authors.forename: Blake
authors.initials: B
authors.lastname: Riggs
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000502:physiology*; D016764:Cell Polarity / Q000502:physiology; D004330:Drosophila / Q000196:embryology / Q000378:metabolism; D029721:Drosophila Proteins / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D008938:Mitosis / Q000502:physiology; D009474:Neurons / Q000378:metabolism*; D008941:Spindle Apparatus / Q000378:metabolism; D013234:Stem Cells / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D029721:Drosophila Proteins