Research Article

Hoxa2- and Rhombomere-Dependent Development of the Mouse Facial Somatosensory Map

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Science  08 Sep 2006:
Vol. 313, Issue 5792, pp. 1408-1413
DOI: 10.1126/science.1130042

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In the mouse trigeminal pathway, sensory inputs from distinct facial structures, such as whiskers or lower jaw and lip, are topographically mapped onto the somatosensory cortex through relay stations in the thalamus and hindbrain. In the developing hindbrain, the mechanisms generating such maps remain elusive. We found that in the principal sensory nucleus, the whisker-related map is contributed by rhombomere 3–derived neurons, whereas the rhombomere 2–derived progeny supply the lower jaw and lip representation. Moreover, early Hoxa2 expression in neuroepithelium prevents the trigeminal nerve from ectopically projecting to the cerebellum, whereas late expression in the principal sensory nucleus promotes selective arborization of whisker-related afferents and topographic connectivity to the thalamus. Hoxa2 inactivation further results in the absence of whisker-related maps in the postnatal brain. Thus, Hoxa2- and rhombomere 3–dependent cues determine the whisker area map and are required for the assembly of the whisker-to-barrel somatosensory circuit.

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