LAUSR

Transient instruction changes migration The brain neocortex is built by waves of neurons migrating from deep within the brain to the surface layers. Ohtaka-Maruyama et al. found that a layer of neurons that multipolar neurons encounter on their travels instructs the migrating neurons to change phenotype and direction (see the Perspective by Schinder and Lanuza). These subplate neurons form transient glutamatergic synapses with the immature migrants. This results in the migrating multipolar neurons becoming bipolar, more directed, and faster in their final migrations. Science, this issue p. 313; see also p. 265 In the developing mouse neocortex, subplate neurons form transient synapses on immature migrating multipolar neurons. The neocortex exhibits a six-layered structure that is formed by radial migration of excitatory neurons, for which the multipolar-to-bipolar transition of immature migrating multipolar neurons is required. Here, we report that subplate neurons, one of the first neuron types born in the neocortex, manage the multipolar-to-bipolar transition of migrating neurons. By histochemical, imaging, and microarray analyses on the mouse embryonic cortex, we found that subplate neurons extend neurites toward the ventricular side of the subplate and form transient glutamatergic synapses on the multipolar neurons just below the subplate. NMDAR (N-methyl-d-aspartate receptor)–mediated synaptic transmission from subplate neurons to multipolar neurons induces the multipolar-to-bipolar transition, leading to a change in migration mode from slow multipolar migration to faster radial glial-guided locomotion. Our data suggested that transient synapses formed on early immature neurons regulate radial migration.