Growth cone pathfinding and filopodial dynamics are mediated separately by Cdc42 activation.
Although evidence exists that activation of the Rho family GTPase Cdc42 affects axonal development, its specific roles within a growth cone are not well delineated. To evaluate the model that Cdc42 activation regulates growth cone navigation by promoting filopodial activity, we adopted a live analysis strategy that uses transgenic Drosophila lines in which neurons coexpressed constitutively active Cdc42 (Cdc42(V12)) and membrane-targeted green fluorescent protein. We found that growth cones that displayed pathfinding defects exhibited little change in their filopodial activity, whereas others without pathfinding defects exhibited an similar50% increase in their filopodial activity. Moreover, effector loop mutations that were added to the constitutively active Cdc42 (Cdc42(V12C40) and Cdc42(V12A37)) exerted little influence over filopodial activity caused by Cdc42 activation but suppressed the pathfinding defects of the growth cones. Together, these data suggest that Cdc42 controls filopodial activity in axonal growth cones independently of its effects on their pathfinding.
Kim
Michael D
MD
Department of Cell and Structural Biology, University of Illinois, Urbana, Illinois 61801, USA.
Kolodziej
Peter
P
Chiba
Akira
A
D019943:Amino Acid Substitution; D000818:Animals; D030801:Animals, Genetically Modified; D001369:Axons / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D002478:Cells, Cultured; D004330:Drosophila; D004625:Embryo, Nonmammalian / Q000294:innervation; D015870:Gene Expression; D049452:Green Fluorescent Proteins; D020439:Growth Cones / Q000187:drug effects / Q000378:metabolism*; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008164:Luminescent Proteins / Q000096:biosynthesis / Q000235:genetics; D018715:Microscopy, Video; D009046:Motor Neurons / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D016297:Mutagenesis, Site-Directed; D009475:Neurons, Afferent / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D011554:Pseudopodia / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D019076:Transgenes; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology
D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins; D020764:cdc42 GTP-Binding Protein