Heterotrimeric kinesin-II is required for the assembly of motile 9+2 ciliary axonemes on sea urchin embryos.
Heterotrimeric kinesin-II is a plus end- directed microtubule (MT) motor protein consisting of distinct heterodimerized motor subunits associated with an accessory subunit. To probe the intracellular transport functions of kinesin-II, we microinjected fertilized sea urchin eggs with an anti-kinesin-II monoclonal antibody, and we observed a dramatic inhibition of ciliogenesis at the blastula stage characterized by the assembly of short, paralyzed, 9+0 ciliary axonemes that lack central pair MTs. Control embryos show no such defect and form swimming blastulae with normal, motile, 9+2 cilia that contain kinesin-II as detected by Western blotting. Injection of anti-kinesin-II into one blastomere of a two-cell embryo leads to the development of chimeric blastulae covered on one side with short, paralyzed cilia, and on the other with normal, beating cilia. We observed a unimodal length distribution of short cilia on anti-kinesin-II-injected embryos corresponding to the first mode of the trimodal distribution of ciliary lengths observed for control embryos. This short mode may represent a default ciliary assembly intermediate. We hypothesize that kinesin-II functions during ciliogenesis to deliver ciliary components that are required for elongation of the assembly intermediate and for formation of stable central pair MTs. Thus, kinesin-II plays a critical role in embryonic development by supporting the maturation of nascent cilia to generate long motile organelles capable of producing the propulsive forces required for swimming and feeding.
Morris
R L
RL
Section of Molecular and Cellular Biology, University of California, Davis, California 95616, USA.
Scholey
J M
JM
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001755:Blastocyst / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure; D002135:Calcium-Binding Proteins / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000502:physiology*; D002453:Cell Cycle; D002678:Chimera; D002875:Chromosomes / Q000502:physiology* / Q000648:ultrastructure; D002923:Cilia / Q000502:physiology* / Q000648:ultrastructure; D004625:Embryo, Nonmammalian / Q000502:physiology*; D016547:Kinesins / Q000502:physiology; D008854:Microscopy, Electron; D009068:Movement; D009124:Muscle Proteins / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000502:physiology*; D012617:Sea Urchins / Q000196:embryology
D000906:Antibodies; D002135:Calcium-Binding Proteins; D009124:Muscle Proteins; C074152:kinesin-II; D016547:Kinesins