title: Microtubule-associated protein 9 (Map9/Asap) is required for the early steps of zebrafish development.
abstract: Microtubules are structural components of the cell cytoskeleton and key factors for mitosis and ciliogenesis in eukaryotes. The regulation of MT dynamics requires non-motor MAPs. We previously showed that, in human cells in culture, MAP9 (also named ASAP) is involved in MT dynamics and is essential for mitotic spindle formation and mitosis progression. Indeed, misexpression of MAP9 leads to severe mitotic defects and cell death. Here, we investigated the in vivo role of map9 during zebrafish development. Map9 is expressed mainly as a maternal gene. Within cells, Map9 is associated with the MT network of the mitotic spindle and with centrosomes. Morpholino-mediated depletion of map9 leads to early development arrest before completion of epiboly. Map9 localizes to the MT array of the YSL. This MT network is destroyed in Map9-depleted embryos, and injection of anti-map9 morpholinos directly in the nascent YSL leads to arrest of epiboly/gastrulation. Finally, map9 knockdown deregulates the expression of genes involved in endodermal differentiation, dorso-ventral and left-right patterning, and other MT-based functions. At low morpholino doses, the surviving embryos show dramatic developmental defects, spindle and mitotic defects, and increased apoptosis. Our findings suggest that map9 is a crucial factor in early zebrafish development by regulating different MT-based processes.
authors.affiliation: Institute of Human Genetics; UPR 1142; CNRS; Montpellier, France; Université de Montpellier 1; Montpellier, France.
authors.forename: Laura
authors.initials: L
authors.lastname: Fontenille
authors.affiliation: Institute of Human Genetics; UPR 1142; CNRS; Montpellier, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Rouquier
authors.affiliation: Dynamique des Interactions Membranaires Normales et Pathologiques; UMR 5235; CNRS; Universités de Montpellier 1&2; Montpellier, France.
authors.forename: Georges
authors.initials: G
authors.lastname: Lutfalla
authors.affiliation: Institute of Human Genetics; UPR 1142; CNRS; Montpellier, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Giorgi
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008938:Mitosis / Q000502:physiology; D015398:Signal Transduction; D008941:Spindle Apparatus / Q000378:metabolism; D015027:Zebrafish / Q000196:embryology / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D008869:Microtubule-Associated Proteins; D029961:Zebrafish Proteins; C000597202:microtubule-associated protein 9, zebrafish
keywords: development; epiboly; gastrulation; knockdown; microtubule-associated protein; microtubules; mitosis; yolk syncytial layer; zebrafish