title: Progressive sheet-to-tubule transformation is a general mechanism for endoplasmic reticulum partitioning in dividing mammalian cells.
abstract: The endoplasmic reticulum (ER) is both structurally and functionally complex, consisting of a dynamic network of interconnected sheets and tubules. To achieve a more comprehensive view of ER organization in interphase and mitotic cells and to address a discrepancy in the field (i.e., whether ER sheets persist, or are transformed to tubules, during mitosis), we analyzed the ER in four different mammalian cell lines using live-cell imaging, high-resolution electron microscopy, and three dimensional electron microscopy. In interphase cells, we found great variation in network organization and sheet structures among different cell lines. In mitotic cells, we show that the ER undergoes both spatial reorganization and structural transformation of sheets toward more fenestrated and tubular forms. However, the extent of spatial reorganization and sheet-to-tubule transformation varies among cell lines. Fenestration and tubulation of the ER correlates with a reduced number of membrane-bound ribosomes.
authors.affiliation: Electron Microscopy Unit, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland.
authors.forename: Maija
authors.initials: M
authors.lastname: Puhka
authors.forename: Merja
authors.initials: M
authors.lastname: Joensuu
authors.forename: Helena
authors.initials: H
authors.lastname: Vihinen
authors.forename: Ilya
authors.initials: I
authors.lastname: Belevich
authors.forename: Eija
authors.initials: E
authors.lastname: Jokitalo
mesh_terms: D000818:Animals; D016466:CHO Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D006224:Cricetinae; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure*; D006801:Humans; D008938:Mitosis; D008954:Models, Biological; D012270:Ribosomes / Q000378:metabolism; D059008:Time-Lapse Imaging; D014709:Vero Cells