title: Correlated light and electron microscopy observations of the uterine epithelial cell actin cytoskeleton using fluorescently labeled resin-embedded sections.
abstract: In order to perform correlative light and electron microscopy (CLEM) more precisely, we have modified existing specimen preparation protocols allowing fluorescence retention within embedded and sectioned tissue, facilitating direct observation across length scales. We detail a protocol which provides a precise correlation accuracy using accessible techniques in biological specimen preparation. By combining a pre-embedding uranyl acetate staining step with the progressive lowering of temperature (PLT) technique, a methacrylate embedded tissue specimen is ultrathin sectioned and mounted onto a TEM finder grid for immediate viewing in the confocal and electron microscope. In this study, the protocol is applied to rat uterine epithelial cells in vivo during early pregnancy. Correlative overlay data was used to track changes in filamentous actin that occurs in these cells from fertilization (Day 1) to implantation on Day 6 as part of the plasma membrane transformation, a process essential in the development of uterine receptivity in the rat. CLEM confirmed that the actin cytoskeleton is disrupted as apical microvilli are progressively lost toward implantation, and revealed the thick and continuous terminal web is replaced by a thinner and irregular actin band, with individually distinguishable filaments connecting actin meshworks which correspond with remaining plasma membrane protrusions.
authors.affiliation: School of Medical Sciences (Discipline of Anatomy and Histology)-The Bosch Institute, The University of Sydney, NSW 2006, Australia. Electronic address: chad.moore@sydney.edu.au.
authors.forename: Chad L
authors.initials: CL
authors.lastname: Moore
authors.affiliation: School of Medical Sciences (Discipline of Anatomy and Histology)-The Bosch Institute, The University of Sydney, NSW 2006, Australia.
authors.forename: Delfine
authors.initials: D
authors.lastname: Cheng
authors.affiliation: School of Medical Sciences (Discipline of Anatomy and Histology)-The Bosch Institute, The University of Sydney, NSW 2006, Australia.
authors.forename: Gerald J
authors.initials: GJ
authors.lastname: Shami
authors.affiliation: School of Medical Sciences (Discipline of Anatomy and Histology)-The Bosch Institute, The University of Sydney, NSW 2006, Australia.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Murphy
mesh_terms: D008841:Actin Cytoskeleton / Q000648:ultrastructure*; D000818:Animals; D004847:Epithelial Cells / Q000648:ultrastructure*; D005260:Female; D016591:Histocytological Preparation Techniques / Q000379:methods*; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission / Q000379:methods; D008856:Microscopy, Fluorescence / Q000379:methods; D011247:Pregnancy; D051381:Rats; D013194:Staining and Labeling / Q000379:methods; D014599:Uterus / Q000166:cytology / Q000502:physiology / Q000648:ultrastructure*
keywords: Actin; Confocal microscopy; Correlative microscopy; Cytoskeleton; Transmission electron microscopy; Uterine epithelium