Facial motor neuron migration advances

- Facial branchiomotor neurons migrate tangentially through the vertebrate hindbrain.
- Genetics and imaging are providing new insights into FBM neuron migration processes.
- Planar cell polarity plays both intrinsic and extrinsic roles in neuron migration.
- Pre-laid axon tracts provide structural cues for FBM neurons to migrate along.
- Migration occurs in both mouse and zebrafish, but mechanistic details differ.

During development, the migration of specific neuronal subtypes is required for the correct establishment of neural circuits. In mice and zebrafish, facial branchiomotor (FBM) neurons undergo a tangential migration from rhombomere 4 caudally through the hindbrain. Recent advances in the field have capitalized on genetic studies in zebrafish and mouse, and high-resolution time-lapse imaging in zebrafish. Planar cell polarity signaling has emerged as a critical conserved factor in FBM neuron migration, functioning both within the neurons and their environment. In zebrafish, migration depends on specialized 'pioneer' neurons to lead follower FBM neurons through the hindbrain, and on interactions with structural components including pre-laid axon tracts and the basement membrane. Despite fundamental conservation, species-specific differences in migration mechanisms are being uncovered.