Neuronal migration occurs through contact-dependent mechanisms [requiring cell-adhesion molecules (CAMs)] and contact-independent mechanisms (involving diffusible molecules). Classic cadherins are calcium-dependent homophilic CAMs with roles in neuronal development and in the migration of non-neuronal cells;Murakami and colleagues now provide the first evidence (on p. 1923) that they also contribute to contact-dependent neuronal migration. The authors focused on the lateral reticular nucleus (LRN) and external cuneate nucleus (ECN) neurons that relay information to the cerebellum. They showed that cadherin mRNAs(specifically CAD6, CAD8, CAD11 and NCAD) are expressed in the migratory streams of LRN and ECN neurons in vivo, and that dominant-negative NCAD perturbs neuron migration in vitro and in vivo. But through what mechanism?Dominant-negative cadherin does not change the responsiveness of neurons to the attractive guidance molecules arising from the floor plate; neither does it affect TAG1, known to be involved in their migration. Instead, the authors suggest that cadherins' adhesive...

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