Lpd depletion reveals that SRF specifies radial versus tangential migration of pyramidal neurons

Abstract

During corticogenesis, pyramidal neurons (~80% of cortical neurons) arise from the ventricular zone (VZ) pass through a multipolar stage to become bipolar and attach to radial glia1, 3, and then migrate to their proper position within the cortex1, 2. As pyramidal neurons migrate radially, they remain attached to their glial substrate as they pass through the subventricular (SVZ) and intermediate (IZ) zones, regions rich in tangentially migrating interneurons and axon fiber tracts. We examined the role of Lamellipodin (Lpd), a homolog of a key regulator of neuronal migration and polarization in C. elegans, in corticogenesis. Lpd depletion caused bipolar pyramidal neurons to adopt a tangential, rather than radial-glial, migration mode without affecting cell fate. Mechanistically, Lpd depletion reduced the activity of SRF, a transcription factor regulated by changes in the ratio of polymerized to unpolymerized actin. Therefore, Lpd depletion exposes a role for SRF in directing pyramidal neurons to select a radial migration pathway along glia rather than a tangential migration mode.