The Complex Dynamic Network of Microtubule and Microfilament Cytasters of the Leech Zygote

• Published in: Developmental biology 2000-12, Vol.228 (1), p.136-149
• Main Authors: Cantillana, Viviana, Urrutia, Milena, Ubilla, Andrea, Fernández, Juan
• Format: Article
• Language: English
• Subjects: Actin Cytoskeleton - drug effects; Actin Cytoskeleton - metabolism; Actin Cytoskeleton - ultrastructure; Actins - metabolism; Adenylyl Imidodiphosphate - pharmacology; Animals; Biological Transport - drug effects; Centrosome - drug effects; Centrosome - metabolism; Centrosome - ultrastructure; cytasters; cytoskeleton assembly; cytoskeleton dynamics; cytoskeleton organization centers; Immunohistochemistry; Interphase - drug effects; leech zygote; Leeches - cytology; Leeches - drug effects; Leeches - metabolism; Leeches - ultrastructure; Meiosis - drug effects; Microinjections; Microscopy, Electron; Microscopy, Fluorescence; Microscopy, Video; Microtubule-Organizing Center - drug effects; Microtubule-Organizing Center - metabolism; Microtubule-Organizing Center - ultrastructure; Microtubules - drug effects; Microtubules - metabolism; Microtubules - ultrastructure; mitochondria transport; Movement - drug effects; ooplasmic segregation; Organelles - drug effects; Organelles - metabolism; Organelles - ultrastructure; Paclitaxel - pharmacology; Theromyzon trizonare; Tubulin - metabolism; Zygote - cytology; Zygote - drug effects; Zygote - metabolism; Zygote - ultrastructure; zygote cytoskeleton
• ISSN: 0012-1606; 1095-564X
• DOI: 10.1006/dbio.2000.9931

The organization of the cytoskeleton in the early first interphase zygote and its involvement in organelle redistribution were studied in the glossiphoniid leech Theromyzon trizonare by confocal and electron microscopy, immunofluorescence, and time-lapse video imaging after microinjection of labeled tubulin and/or actin and loading with a mitotracker. The cytoskeleton consists of an inner or endoplasmic and an outer or ectoplasmic domain. The inner domain consists of a monaster whose fibers retract from the zygote periphery by the end of the early first interphase. The outer domain is built upon a network of microtubules and microfilaments cytasters. Short pulses of microinjected labeled actin or tubulin and Taxol treatment demonstrate that cytasters are centers of microtubule and microfilament nucleation. Immunostaining with anti-centrophilin, anti-BX-63, and anti-AH-6 indicates that the network of cytasters includes centrosomal antigens. Cytasters move in an orderly fashion at speeds of 0.5–2 μm/min, in an energy-dependent process retarded and finally blocked by the ATP analogue AMP–PNP and high concentrations of Taxol. Colliding cytasters fuse and form larger cytoskeletal nucleation centers. The leech zygote is a highly compartmentalized cell whose cytasters function as articulated components of a very dynamic cytoskeletal system engaged in bulk transportation of organelles during ooplasmic segregation.