The proper function of the nervous system relays in the balanced activity of excitatory and inhibitory signals. The formation of the circuits, substrate of such activity is the result of a complex process in which neuronal migration plays a central role. In the cerebral cortex, pyramidal neurons (excitatory) and interneurons (inhibitory) originate form different sources and have distinct –radial and tangential respectively- migratory routes.

Cell migration results from the repetition of a cycle that starts with the elongation of the leading process. This is followed by the movement of the nucleus inside the process and the retraction of the trailing process. Neurons have been often described with a bipolar morphology during migration, although there are exceptions to this rule. Cortical GABAergic interneurons represent the most significant example of migrating neurons with multiple processes. The question that arises in relation to the branched morphology of interneurons is how the cell uses the two leading processes that explore a wide prospective territory to navigate. We have performed time-lapse experiments in interneurons migrating in cortical slices, a three dimensional context where the migratory signals are preserved and found that the branches play a central role in the migratory program. The bifurcations are landmarks where the nucleus wait until one of the branches is stabilized and the other is retracted. We are also analyzing the intracellular distribution of small GTPases, components of the cytoskeleton and intracellular calcium to correlate signaling events with branch dynamics and cell navigation. Supported by Grant BFU2005–02393