effect. Actin stabilizing proteins are also involved and are essential for continued protrusion of filopodia and lamellipodia in the presence of attractive cues, while actin destabilizing proteins are involved in the presence of a repulsive cue. A similar process is involved with microtubules. In the presence of an attractive cue on one side of the growth cone, specific microtubules are targeted on that side by microtubule stabilizing proteins, resulting in growth cone turning in the direction of the positive stimulus. With repulsive cues, the opposite is true: microtubule stabilization is favored on the opposite side of the growth cone as the negative stimulus resulting in the growth cone turning away from the repellent. This process coupled with actin-associated processes result in the overall directed growth of an axon. Growth cone receptors detect the presence of axon guidance molecules such as Netrin, Slit, Ephrins, and Semaphorins. It has more recently been shown that cell fate determinants such as Wnt or Shh can also act as guidance cues. The same guidance cue can act as an attractant or a repellent, depending on context. A prime example of this is Netrin-1, which signals attraction through the DCC receptor and repulsion through the Unc-5 receptor. Furthermore, it has been discovered that these same molecules are involved in guiding vessel growth. Axon guidance directs the initial wiring of the nervous system and is also important in axonal regeneration following an injury. References Developmental neuroscience Actin-based structures