Axon Guidance Mechanisms and Assays

What is retrograde tracing in axon guidance?

A method involving the injection of a dye (RD) into a limb, allowing for the retrograde diffusion of the dye along axons to analyze which neurons are labeled in the spinal cord.

What does retrograde tracing reveal about neurons in the spinal cord?

Injection of RD in the ventral limb labels medial neurons, while injection in the dorsal limb labels lateral neurons.

What role does Sema-3F play in axon guidance?

Sema-3F is rich in the dorsal region and repels neurons; if removed or if the nrp-1 receptor is absent, neurons are not repelled and can cross into the dorsal region.

What are the functions of Netrin in axon guidance?

Netrin is a guidance cue that binds to DCC (attraction) and Unc-5 (repulsion) receptors; if Netrin binds to DCC, it is attractive, while binding to Unc-5 is repulsive.

What is the purpose of the growth cone turning assay?

To test the guidance effect on neurons in culture by inserting a pipette at a 45° angle with a concentration gradient and observing the growth cone's movement.

What is the role of Slits in axon guidance?

Slits act as guidance cues by binding to Robo receptors.

How do morphogens function in later stages of development regarding axon guidance?

Morphogens act as guidance cues that influence the direction of axon growth.

What is a co-culture assay in the context of axon guidance?

An experimental setup where a dish with an explant of neurons is placed next to cells releasing guidance cues (like Writ) to compare against an explant alone (control).

What are the general mechanisms of growth cone turning?

1) Asymmetric receptor signaling and regulation at the plasma membrane, including trafficking of receptors via exocytosis and endocytosis. 2) Generation of second messengers and signal transduction cascades.

What is the significance of second messengers in growth cone turning?

Second messengers play a crucial role in integrating signals that can switch the response of the growth cone between attractive and repulsive.