RESUMO
Rho family GTPases are thought to regulate actin-dependent processes, but their functions in vivo are still poorly understood. We have investigated the function of a new, widely expressed Rho family member in C. elegans by analyzing mutations in the endogenous gene. Activated and null alleles all inhibit cell migration, demonstrating that this protein is required for cell migration in vivo. Only a small subset of the migrations inhibited by activating mutations are inhibited by null mutations, suggesting that considerable functional redundancy exists within this system. Our findings support this conclusion and show that mig-2 functions redundantly with another pathway to regulate nuclear migration. Surprisingly, activated alleles also cause misguided axon growth, suggesting that Rho family GTPases may couple guidance cues to process outgrowth.
Assuntos
Axônios/fisiologia , Caenorhabditis elegans/genética , Movimento Celular/fisiologia , GTP Fosfo-Hidrolases/genética , Proteínas de Ligação ao GTP/genética , Neurônios/citologia , Alelos , Animais , Animais Geneticamente Modificados , Axônios/química , Caenorhabditis elegans/química , Caenorhabditis elegans/citologia , Membrana Celular/química , Clonagem Molecular , GTP Fosfo-Hidrolases/análise , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Helminto/genética , Dados de Sequência Molecular , Mutação/fisiologia , Neurônios/química , Neurônios/ultraestrutura , Homologia de Sequência de AminoácidosRESUMO
An assay employing patterned laminin substrata was used to screen for compounds that disrupt neurite guidance. One molecule, pertussis toxin, caused neurites to wander from patterns that normally guided them, yet had no significant effect on rates of neurite outgrowth. Wandering was greatest on patterns requiring frequent guidance (e.g., laminin stripes with periodic gaps). Surprisingly, the B oligomer of pertussis toxin, which lacks the subunit that inactivates G proteins, was equipotent at disrupting neurite guidance. Pertussis toxin probably acts by binding cell surface carbohydrates, since neurites lacking complex-type N-linked oligosaccharides were insensitive to the effects of the toxin. The B oligomer also blocked growth cone collapse induced by a brain membrane-derived factor; such factors are thought to act as repulsive guidance cues in vivo. That a single reagent can inhibit neuronal responses to both attractive and repulsive guidance cues suggests that such cues may share signaling pathways.
