Cytoskeletal dynamics in growth-cone steering

Abstract

Interactions between dynamic microtubules and actin filaments are essential to a wide range of cell biological processes including cell division, motility and morphogenesis. In neuronal growth cones, interactions between microtubules and actin filaments in filopodia are necessary for growth cones to make a turn. Growth-cone turning is a fundamental behaviour during axon guidance, as correct navigation of the growth cone through the embryo is required for it to locate an appropriate synaptic partner. Microtubule-actin filament interactions also occur in the transition zone and central domain of the growth cone, where actin arcs exert compressive forces to corral microtubules into the core of the growth cone and thereby facilitate microtubule bundling, a requirement for axon formation. We now have a fairly comprehensive understanding of the dynamic behaviour of the cytoskeleton in growth cones, and the stage is set for discovering the molecular machinery that enables microtubule-actin filament coupling in growth cones, as well as the intracellular signalling pathways that regulate these interactions. Furthermore, recent experiments suggest that microtubule-actin filament interactions might also be important for the formation of dendritic spines from filopodia in mature neurons. Therefore, the mechanisms coupling microtubules to actin filaments in growth-cone turning and dendritic-spine maturation might be conserved.

The Microtubule Plus-End Tracking Proteins SPR1 and EB1b Interact to Maintain Polar Cell Elongation and Directional Organ Growth in Arabidopsis

“…+TIPs in animals have been shown to facilitate mitotic spindle formation/function as well as to regulate brain and muscle development, cell differentiation, cell migration including protrusion shape, and cell polarity (Barth et al, 2008;Jaworski et al, 2008;Geraldo and Gordon-Weeks, 2009;Minc et al, 2009;Morrison, 2009;Zhang et al, 2009;Brüning-Richardson et al, 2011;Gierke and Wittmann, 2012;Schober et al, 2012). EB1b and SPR1 are two +TIPs found to regulate directional organ growth in the model plant Arabidopsis (Nakajima et al, 2004;Sedbrook et al, 2004;Bisgrove et al, 2008).…”

Hts, the Drosophila homologue of adducin, physically interacts with the transmembrane receptor golden goal to guide photoreceptor axons

“…The barbed ends of the F-Actin bundles point distally, so that F-Actin assembly takes place at the very tip of the filopodium. This produces a force on the F-Actin bundle that moves the bundle rearwards (retrograde flow) and a force on the plasma membrane that extends the filopodium (Geraldo and Gordon-Weeks, 2009). Actin assembly and retrograde flow are regulated independently (Mallavarapu and Mitchison, 1999).…”

“…Actin assembly and retrograde flow are regulated independently (Mallavarapu and Mitchison, 1999). F-Actin capping proteins influence the rate of Actin assembly (Pollard and Cooper, 1986;Mallavarapu and Mitchison, 1999), whereas the rate of retrograde F-Actin flow has been suggested to be regulated by a ''clutch'' that links the cytoskeleton via transmembrane proteins to the extracellular matrix and thereby countervails the retrograde F-Actin flow (Suter and Forscher, 2000;Bard et al, 2008;Chan and Odde, 2008;Geraldo and Gordon-Weeks, 2009). …”

Neuron Subpopulations with Different Elongation Rates and DCC Dynamics Exhibit Distinct Responses to Isolated Netrin-1 Treatment

“…3 Biochemical guidance cues can be either substrate-bound or soluble, affecting the axons either locally or over long distances. [4][5] The major guidance cue families are Slits and Semaphorins (repellent), Ephrins (attractant) and Netrins. 4 Netrin-1, the best characterized member of the Netrins family, acts not only as a guidance molecule but also as a growth factor.…”